From 02490f521e06597800c396c985bed4cd01189fcf Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Thu, 6 Jul 2023 16:00:11 +0200
Subject: [PATCH 01/32] Add test for ploutos large graph pattern.

---
 .../engine/reasoner/api/MatchTest.java        | 42 +++++++++++++++++++
 .../knowledge/engine/reasoner/api/Util.java   | 35 +++++++++++++---
 .../knowledge/engine/rest/api/RestServer.java |  3 ++
 3 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
index 790f69f1..7f6a8bf1 100644
--- a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
+++ b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
@@ -13,6 +13,7 @@
 import java.util.Map;
 import java.util.Set;
 
+import org.apache.jena.atlas.logging.Log;
 import org.apache.jena.sparql.sse.SSE;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
@@ -540,4 +541,45 @@ public void testTranslateEmptyBindingSet() {
 
 		assertTrue(tvbs2.isEmpty());
 	}
+
+	@Test
+	public void testPloutosGPMatcher() {
+
+		String gp = """
+				?operation <type> <HarvestingOperation> .
+				?operation <hasOutput> ?output .
+				?operation <isOperatedOn> ?parcel .
+				?parcel <contains> ?crop .
+				?crop <type> ?cropType .
+				?cropType <label> ?cropName .
+				?parcel <hasArea> ?area .
+				?farm <type> <Farm> .
+				?farm <location> ?location .
+				?location <lat> ?latitude .
+				?location <long> ?longitude .
+				?farm <hasName> ?farmName .
+				?farm <contains> ?parcel .
+				?farmer <managesFarm> ?farm .
+				?association <type> <FarmAssociation> .
+				?farmer <isMemberOf> ?association .
+				?association <hasName> ?associationName .
+				?parcel <hasAdministrator> ?parcelAdminName .
+				?parcel <hasToponym> ?parcelToponym .
+				?parcel <inRegion> ?parcelRegion .
+				?output <isMeantFor> ?purpose .
+				?parcel <hasCultivator> ?cultivatorName .
+				?farm <hasCountry> ?country .
+				?country <name> ?countryLabel .""";
+
+		Set<TriplePattern> obj = Util.toGP(gp);
+
+		Rule r = new Rule(new HashSet<>(), obj);
+
+		System.out.println("NrOfMatches with " + obj.size() + " triple patterns: " + getNumberOfMatches(obj.size()));
+
+		Set<Match> findMatchesWithConsequent = r.consequentMatches(obj, MatchStrategy.FIND_ONLY_BIGGEST_MATCHES);
+
+		System.out.println("Size: " + findMatchesWithConsequent.size());
+
+	}
 }
diff --git a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/Util.java b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/Util.java
index 3297ae4e..9bb362c8 100644
--- a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/Util.java
+++ b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/Util.java
@@ -4,6 +4,8 @@
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.nio.charset.StandardCharsets;
+import java.util.HashSet;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.apache.jena.graph.Node;
@@ -15,10 +17,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import eu.knowledge.engine.reasoner.api.Binding;
-import eu.knowledge.engine.reasoner.api.BindingSet;
-import eu.knowledge.engine.reasoner.api.TriplePattern;
-
 public class Util {
 
 	private static final Logger LOG = LoggerFactory.getLogger(Util.class);
@@ -92,7 +90,7 @@ public static Model generateModel(TriplePattern tp, BindingSet variableBindings)
 						if (b.get(n.getName()).isURI()) {
 							repr = "<" + b.get(n.getName()).toString() + ">";
 						} else {
-							repr = b.get(n.getName()).toString(); //"\"" + b.get(n.getName()).toString() + "\"";
+							repr = b.get(n.getName()).toString(); // "\"" + b.get(n.getName()).toString() + "\"";
 						}
 
 						LOG.trace("Parsing: {}", repr);
@@ -109,4 +107,31 @@ public static Model generateModel(TriplePattern tp, BindingSet variableBindings)
 		return m;
 	}
 
+	/**
+	 * parses every line of the string into a triple pattern and combines them into
+	 * a set. Note that if it ends with a period (.) it will be removed.
+	 * 
+	 * @param gp
+	 * @return
+	 */
+	public static Set<TriplePattern> toGP(String gp) {
+
+		var set = new HashSet<TriplePattern>();
+		String[] lines = gp.split("\n");
+
+		for (String line : lines) {
+
+			String trimmed = line.strip();
+			if (trimmed.endsWith("."))
+				trimmed = trimmed.substring(0, trimmed.length() - 2);
+
+			if (!trimmed.isEmpty()) {
+				System.out.println("line: " + trimmed);
+				set.add(new TriplePattern(trimmed));
+			}
+		}
+
+		return set;
+	}
+
 }
diff --git a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/RestServer.java b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/RestServer.java
index 170b8fb0..66e294dc 100644
--- a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/RestServer.java
+++ b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/RestServer.java
@@ -1,5 +1,7 @@
 package eu.knowledge.engine.rest.api;
 
+import java.net.InetSocketAddress;
+
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.servlet.ServletContextHandler;
 import org.eclipse.jetty.servlet.ServletHolder;
@@ -28,6 +30,7 @@ public static void main(String[] args) {
 		}
 
 		LOG.info("Starting Knowledge Engine REST API on port {}.", port);
+
 		Server server = new Server(port);
 		System.setProperty("org.jboss.logging.provider", "slf4j");
 		ServletContextHandler ctx = new ServletContextHandler(ServletContextHandler.NO_SESSIONS);

From b2b73237ed751eedab1fb9c8f3550600e7fea6db Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 11 Aug 2023 12:01:22 +0200
Subject: [PATCH 02/32] Merge branch 'master' of
 git@github.com:TNO/knowledge-engine.git

---
 .../main/java/eu/knowledge/engine/reasoner/BaseRule.java  | 8 ++++++++
 .../java/eu/knowledge/engine/reasoner/api/MatchTest.java  | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/reasoner/src/main/java/eu/knowledge/engine/reasoner/BaseRule.java b/reasoner/src/main/java/eu/knowledge/engine/reasoner/BaseRule.java
index 7ccf4fe5..0655be69 100644
--- a/reasoner/src/main/java/eu/knowledge/engine/reasoner/BaseRule.java
+++ b/reasoner/src/main/java/eu/knowledge/engine/reasoner/BaseRule.java
@@ -14,6 +14,8 @@
 import java.util.concurrent.CompletableFuture;
 
 import org.apache.jena.sparql.core.Var;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import eu.knowledge.engine.reasoner.api.Binding;
 import eu.knowledge.engine.reasoner.api.BindingSet;
@@ -23,6 +25,8 @@
 
 public class BaseRule {
 
+	private static final Logger LOG = LoggerFactory.getLogger(BaseRule.class);
+
 	public static final String EMPTY = "";
 
 	public static final String ARROW = "->";
@@ -178,7 +182,11 @@ public static Set<Match> matches(Set<TriplePattern> aFirstPattern, Set<TriplePat
 			biggestMatches.addAll(matchIter.next().getValue());
 		}
 
+		int idx = 0;
 		while (matchIter.hasNext()) {
+			idx++;
+			LOG.trace("Processing triple pattern {}/{} with {} biggest and {} smaller matches.", idx,
+					matchesPerTriple.size(), biggestMatches.size(), smallerMatches.size());
 
 			long innerStart = System.currentTimeMillis();
 
diff --git a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
index 7f6a8bf1..c9314e90 100644
--- a/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
+++ b/reasoner/src/test/java/eu/knowledge/engine/reasoner/api/MatchTest.java
@@ -13,8 +13,8 @@
 import java.util.Map;
 import java.util.Set;
 
-import org.apache.jena.atlas.logging.Log;
 import org.apache.jena.sparql.sse.SSE;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 import org.junit.jupiter.api.TestInstance.Lifecycle;
@@ -542,6 +542,7 @@ public void testTranslateEmptyBindingSet() {
 		assertTrue(tvbs2.isEmpty());
 	}
 
+	@Disabled // this unit test causes a out of memory after about 30 to 45 minutes.
 	@Test
 	public void testPloutosGPMatcher() {
 

From 8d815aa8213c6bdf6896b5a4ab5b5849bbbf8dbc Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 29 Sep 2023 08:35:13 +0200
Subject: [PATCH 03/32] Prevent ConcurrentModificationExceptions in
 MessageDispatcher.

---
 .../smartconnector/runtime/messaging/MessageDispatcher.java    | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
index 8d9cb2c0..c72a9ac5 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.net.URI;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -74,7 +75,7 @@ private static enum State {
 	 * replying to this message. Instead, we wait until the (remote) known Smart
 	 * Connectors change, and then try again.
 	 */
-	private final List<KnowledgeMessage> undeliverableMail = new LinkedList<>();
+	private final List<KnowledgeMessage> undeliverableMail = Collections.synchronizedList(new LinkedList<>());
 
 	/**
 	 * Construct the {@link MessageDispatcher} in a distributed mode, with an

From 7f26e4ab2a3386a99fdfd153d4c0c731b4a60637 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Wed, 4 Oct 2023 21:01:04 +0200
Subject: [PATCH 04/32] Improved the handling of connection errors.

Todo:
- remove unnecessary log statements
- determine correct delays in RemoteKerConnection.
---
 .../impl/MessageRouterImpl.java               |   3 +-
 .../impl/ReasonerProcessor.java               |   6 +-
 .../impl/SerialMatchingProcessor.java         |   9 +-
 .../runtime/messaging/MessageDispatcher.java  |   7 +-
 .../messaging/RemoteKerConnection.java        | 204 ++++++++++++------
 .../messaging/RemoteKerConnectionManager.java |  33 ++-
 6 files changed, 182 insertions(+), 80 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
index 4f69d81a..ac55f8c4 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
@@ -103,7 +103,8 @@ public void handleAskMessage(AskMessage message) {
 				try {
 					messageDispatcher.send(reply);
 				} catch (Throwable e) {
-					this.LOG.warn("Could not send reply to message " + message.getMessageId(), e);
+					this.LOG.warn("Could not send reply to message " + message.getMessageId());
+					this.LOG.debug("", e);
 				}
 			}).handle((r, e) -> {
 
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
index 9af8b96a..37c73879 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
@@ -432,7 +432,8 @@ public CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet> handle(
 				});
 
 			} catch (IOException e) {
-				LOG.error("No errors should occur while sending an AskMessage.", e);
+				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), askMessage);
+				LOG.debug("", e);
 				bsFuture = new CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet>();
 				bsFuture.complete(new eu.knowledge.engine.reasoner.api.BindingSet());
 			}
@@ -493,7 +494,8 @@ public CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet> handle(
 				});
 
 			} catch (IOException e) {
-				LOG.error("No errors should occur while sending an PostMessage.", e);
+				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), postMessage);
+				LOG.debug("", e);
 				bsFuture = new CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet>();
 				bsFuture.complete(new eu.knowledge.engine.reasoner.api.BindingSet());
 			}
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
index 23b09e23..45162b92 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
@@ -137,8 +137,8 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 								}
 							});
 						} catch (IOException e) {
-							this.LOG.warn("An error occured while sending and processing a message: {}", e);
-							this.LOG.debug("This is the message where the error occured: {}", askMessage);
+							this.LOG.warn("Error '{}' occurred while sending and processing: {}", e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), askMessage);
+							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.
 							this.checkOtherKnowledgeInteraction(bindingSet);
@@ -187,8 +187,9 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 								}
 							});
 						} catch (IOException e) {
-							this.LOG.warn("An error occured while sending and processing a message: {}", e);
-							this.LOG.debug("This is the message where the error occured: {}", postMessage);
+							
+							this.LOG.warn("Error '{}' occurred while sending and processing: {}", e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), postMessage);
+							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.
 							this.checkOtherKnowledgeInteraction(bindingSet);
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
index c72a9ac5..7be4dede 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
@@ -8,7 +8,9 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.LinkedBlockingQueue;
 import java.util.stream.Collectors;
 
 import org.eclipse.jetty.server.Server;
@@ -306,16 +308,19 @@ public void removeListener(KnowledgeDirectoryProxyListener listener) {
 	 * comes.
 	 */
 	private void tryDeliverUndeliveredMail() throws IOException {
+
 		Iterator<KnowledgeMessage> it = undeliverableMail.iterator();
+		Set<KnowledgeMessage> toBeRemoved = new HashSet<>();
 		while (it.hasNext()) {
 			KnowledgeMessage message = it.next();
 			Set<URI> knowledgeBaseIds = this.getKnowledgeBaseIds();
 			if (knowledgeBaseIds.contains(message.getFromKnowledgeBase())) {
 				LOG.info("I can now deliver the message I received from " + message.getFromKnowledgeBase());
 				deliverToLocalSmartConnector(message);
-				it.remove();
+				toBeRemoved.add(message);
 			}
 		}
+		undeliverableMail.removeAll(toBeRemoved);
 	}
 
 	void notifySmartConnectorsChanged() {
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index ef5143b2..5fe1db89 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -1,5 +1,7 @@
 package eu.knowledge.engine.smartconnector.runtime.messaging;
 
+import static eu.knowledge.engine.smartconnector.runtime.messaging.Utils.stripUserInfoFromURI;
+
 import java.io.IOException;
 import java.net.Authenticator;
 import java.net.PasswordAuthentication;
@@ -10,6 +12,7 @@
 import java.net.http.HttpRequest.BodyPublishers;
 import java.net.http.HttpResponse;
 import java.net.http.HttpResponse.BodyHandlers;
+import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -30,7 +33,6 @@
 import eu.knowledge.engine.smartconnector.runtime.messaging.inter_ker.api.RFC3339DateFormat;
 import eu.knowledge.engine.smartconnector.runtime.messaging.inter_ker.model.KnowledgeEngineRuntimeDetails;
 import eu.knowledge.engine.smartconnector.runtime.messaging.kd.model.KnowledgeEngineRuntimeConnectionDetails;
-import static eu.knowledge.engine.smartconnector.runtime.messaging.Utils.stripUserInfoFromURI;
 
 /**
  * This class is responsible for sending messages to a single remote Knowledge
@@ -49,6 +51,9 @@ public class RemoteKerConnection {
 	private final HttpClient httpClient;
 	private final ObjectMapper objectMapper;
 
+	private LocalDateTime tryAgainAfter = null;
+	private int errorCounter = 0;
+
 	public RemoteKerConnection(MessageDispatcher dispatcher,
 			KnowledgeEngineRuntimeConnectionDetails kerConnectionDetails) {
 		this.dispatcher = dispatcher;
@@ -70,7 +75,8 @@ protected PasswordAuthentication getPasswordAuthentication() {
 					}
 				});
 			} else {
-				throw new IllegalArgumentException("Found user information in remote KER URL, but it does not have two parts. Make sure you don't use a colon inside the parts.");
+				throw new IllegalArgumentException(
+						"Found user information in remote KER URL, but it does not have two parts. Make sure you don't use a colon inside the parts.");
 			}
 		} else {
 			this.remoteKerUri = kerConnectionDetails.getExposedUrl();
@@ -83,40 +89,84 @@ protected PasswordAuthentication getPasswordAuthentication() {
 				.setDateFormat(new RFC3339DateFormat());
 	}
 
+	private void noError() {
+		this.errorCounter = 0;
+		this.tryAgainAfter = null;
+	}
+
+	private int errorOccurred() {
+		this.errorCounter++;
+		int waitTime = getWaitTime(this.errorCounter);
+		this.tryAgainAfter = LocalDateTime.now().plusMinutes(waitTime);
+		return waitTime;
+	}
+
 	/**
 	 * Contact the Knowledge Engine Runtime to retrieve the latest
 	 * {@link KnowledgeEngineRuntimeDetails}
 	 */
 	private void updateRemoteKerDataFromPeer() {
 		try {
-			HttpRequest request = HttpRequest
-				.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-				.header("Content-Type", "application/json").GET().build();
+			HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
+					.header("Content-Type", "application/json").GET().build();
 
 			HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
 			if (response.statusCode() == 200) {
 				KnowledgeEngineRuntimeDetails runtimeDetails = objectMapper.readValue(response.body(),
 						KnowledgeEngineRuntimeDetails.class);
-				LOG.info("Successfully received runtimedetails from " + this.remoteKerUri + " with " + runtimeDetails.getSmartConnectorIds().size()
-						+ " Smart Connectors: " + runtimeDetails.getSmartConnectorIds());
+				LOG.info("Successfully received runtimedetails from " + this.remoteKerUri + " with "
+						+ runtimeDetails.getSmartConnectorIds().size() + " Smart Connectors: "
+						+ runtimeDetails.getSmartConnectorIds());
 				// TODO validate
 				this.remoteKerDetails = runtimeDetails;
-				dispatcher.notifySmartConnectorsChanged();
+				noError();
 			} else {
-				LOG.warn("Failed to received runtimedetails from " + this.remoteKerUri + ", got status code " + response.statusCode());
+				this.remoteKerDetails = null;
+				int waitTime = errorOccurred();
+				LOG.warn(
+						"Failed to receive runtimedetails from {}, got status code {}. Trying KER again in {} minutes.",
+						this.remoteKerUri, response.statusCode(), waitTime);
 			}
 		} catch (IOException | URISyntaxException | InterruptedException e) {
-			LOG.warn("Failed to received runtimedetails from " + this.remoteKerConnectionDetails.getId(), e);
+			this.remoteKerDetails = null;
+			int waitTime = errorOccurred();
+			LOG.warn("Failed to receive runtimedetails from " + this.remoteKerConnectionDetails.getId()
+					+ ". Trying KER again in " + waitTime + " minutes.");
+			LOG.debug("", e);
 		}
+		dispatcher.notifySmartConnectorsChanged();
+	}
+
+	private boolean isAvailable() {
+		if (tryAgainAfter != null) {
+			boolean after = LocalDateTime.now().isAfter(tryAgainAfter);
+			if (after) {
+				LOG.info("KER {} available again.", this.remoteKerUri);
+			}
+			return after;
+		} else
+			return true;
 	}
 
 	public KnowledgeEngineRuntimeDetails getRemoteKerDetails() {
-		if (remoteKerDetails == null) {
+		if (this.isAvailable() && remoteKerDetails == null) {
 			updateRemoteKerDataFromPeer();
 		}
+
 		return remoteKerDetails;
 	}
 
+	private int getWaitTime(int i) {
+		if (i == 1)
+			return 1; // 1
+		else if (i == 2)
+			return 2; // 5
+		else if (i == 3)
+			return 5; // 10
+		else
+			return 10; // 15
+	}
+
 	public List<URI> getRemoteSmartConnectorIds() {
 		List<URI> list = new ArrayList<>();
 		KnowledgeEngineRuntimeDetails remoteKerDetails = getRemoteKerDetails();
@@ -129,6 +179,9 @@ public List<URI> getRemoteSmartConnectorIds() {
 				}
 			}
 		}
+
+		LOG.info("Returning {} SCs for {}.", list.size(), this.remoteKerUri);
+
 		return list;
 	}
 
@@ -155,71 +208,98 @@ public void start() {
 	}
 
 	public void stop() {
-		try {
-			HttpRequest request = HttpRequest
-					.newBuilder(
-						new URI(this.remoteKerUri + "/runtimedetails/"
-									+ dispatcher.getKnowledgeDirectoryConnectionManager().getMyKnowledgeDirectoryId()))
-					.header("Content-Type", "application/json").DELETE().build();
+		if (this.isAvailable()) {
+			try {
+				HttpRequest request = HttpRequest
+						.newBuilder(new URI(this.remoteKerUri + "/runtimedetails/"
+								+ dispatcher.getKnowledgeDirectoryConnectionManager().getMyKnowledgeDirectoryId()))
+						.header("Content-Type", "application/json").DELETE().build();
 
-			HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
-			if (response.statusCode() == 200) {
-				LOG.trace("Successfully said goodbye to {}", this.remoteKerUri);
-			} else {
-				LOG.warn("Failed to say goodbye to {}, got response {}: {}",
-						this.remoteKerUri,
-						response.statusCode(), response.body());
+				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				if (response.statusCode() == 200) {
+					LOG.trace("Successfully said goodbye to {}", this.remoteKerUri);
+				} else {
+					LOG.warn("Failed to say goodbye to {}, got response {}: {}", this.remoteKerUri,
+							response.statusCode(), response.body());
+				}
+			} catch (IOException | URISyntaxException | InterruptedException e) {
+				LOG.warn("Failed to say goodby to " + remoteKerConnectionDetails.getId(), e);
 			}
-		} catch (IOException | URISyntaxException | InterruptedException e) {
-			LOG.warn("Failed to say goodby to " + remoteKerConnectionDetails.getId(), e);
-		}
+		} else
+			LOG.info("Still ignoring KER {}.", this.remoteKerUri);
 	}
 
 	public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOException {
-		assert getRemoteKerDetails().getSmartConnectorIds().contains(message.getToKnowledgeBase().toString());
+		assert (getRemoteKerDetails() == null ? true
+				: getRemoteKerDetails().getSmartConnectorIds().contains(message.getToKnowledgeBase().toString()));
 
-		try {
-			String jsonMessage = objectMapper.writeValueAsString(MessageConverter.toJson(message));
-			HttpRequest request = HttpRequest
-					.newBuilder(
-							new URI(this.remoteKerUri + getPathForMessageType(message)))
-					.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
+		if (this.isAvailable()) {
 
-			HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
-			if (response.statusCode() == 202) {
-				LOG.trace("Successfully sent message {} to {}", message.getMessageId(),
-						this.remoteKerUri);
-			} else {
-				LOG.warn("Failed to send message {} to {}, got response {}: {}", message.getMessageId(),
-					this.remoteKerUri, response.statusCode(), response.body());
-				throw new IOException("Message not accepted by remote host, status code " + response.statusCode()
-						+ ", body " + response.body());
+			try {
+				String jsonMessage = objectMapper.writeValueAsString(MessageConverter.toJson(message));
+				HttpRequest request = HttpRequest
+						.newBuilder(new URI(this.remoteKerUri + getPathForMessageType(message)))
+						.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
+
+				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				if (response.statusCode() == 202) {
+					this.noError();
+					LOG.trace("Successfully sent message {} to {}", message.getMessageId(), this.remoteKerUri);
+				} else {
+					this.remoteKerDetails = null;
+					int time = this.errorOccurred();
+					LOG.warn("Ignoring KER {} for {} minutes. Failed to send message {} to {}, got response {}: {}",
+							this.remoteKerUri, time, message.getMessageId(), this.remoteKerUri, response.statusCode(),
+							response.body());
+					dispatcher.notifySmartConnectorsChanged();
+					throw new IOException("Message not accepted by remote host, status code " + response.statusCode()
+							+ ", body " + response.body());
+				}
+			} catch (JsonProcessingException | URISyntaxException | InterruptedException e) {
+				this.remoteKerDetails = null;
+				int time = this.errorOccurred();
+				LOG.warn("Ignoring KER {} for {} minutes.", this.remoteKerUri, time);
+				dispatcher.notifySmartConnectorsChanged();
+				throw new IOException("Could not send message to remote SmartConnector.", e);
+			} catch (IOException e) {
+				this.remoteKerDetails = null;
+				int time = this.errorOccurred();
+				dispatcher.notifySmartConnectorsChanged();
+				LOG.warn("Ignoring KER {} for {} minutes.", this.remoteKerUri, time);
+				throw e;
 			}
-		} catch (JsonProcessingException | URISyntaxException | InterruptedException e) {
-			throw new IOException("Could not send message to remote SmartConnector", e);
+		} else {
+			LOG.warn("Still ignoring KER {}.", this.remoteKerUri);
+			throw new IOException("KER " + this.remoteKerUri + " is currently unavalable. Trying again later.");
 		}
 	}
 
 	public void sendMyKerDetailsToPeer(KnowledgeEngineRuntimeDetails details) {
-		try {
-			String jsonMessage = objectMapper.writeValueAsString(details);
-			HttpRequest request = HttpRequest
-					.newBuilder(
-							new URI(this.remoteKerUri + "/runtimedetails"))
-					.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
+		if (this.isAvailable()) {
+			try {
+				String jsonMessage = objectMapper.writeValueAsString(details);
+				HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
+						.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
 
-			HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
-			if (response.statusCode() == 200) {
-				LOG.trace("Successfully sent updated KnowledgeEngineRuntimeDetails to {}",
-						this.remoteKerUri);
-			} else {
-				LOG.warn("Failed to send updated KnowledgeEngineRuntimeDetails to {}, got response {}: {}",
-					this.remoteKerUri, response.statusCode(), response.body());
+				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				if (response.statusCode() == 200) {
+					this.noError();
+					LOG.trace("Successfully sent updated KnowledgeEngineRuntimeDetails to {}", this.remoteKerUri);
+				} else {
+					this.remoteKerDetails = null;
+					this.errorOccurred();
+					LOG.warn("Failed to send updated KnowledgeEngineRuntimeDetails to {}, got response {}: {}",
+							this.remoteKerUri, response.statusCode(), response.body());
+				}
+			} catch (IOException | URISyntaxException | InterruptedException e) {
+				this.remoteKerDetails = null;
+				this.errorOccurred();
+				LOG.warn("Failed to send updated KnowledgeEngineRuntimeDetails to "
+						+ remoteKerConnectionDetails.getId());
+				LOG.debug("", e);
 			}
-		} catch (IOException | URISyntaxException | InterruptedException e) {
-			LOG.warn("Failed to send updated KnowledgeEngineRuntimeDetails to "
-					+ remoteKerConnectionDetails.getId(), e);
-		}
+		} else
+			LOG.info("Still ignoring KER {}.", this.remoteKerUri);
 	}
 
 	private String getPathForMessageType(KnowledgeMessage message) {
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
index 3acc44ab..8e7b1003 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
@@ -58,15 +58,18 @@ public void start() {
 	}
 
 	public void scheduleQueryKnowledgeDirectory() {
-		if (this.scheduledKnowledgeDirectoryQueryFuture != null && !this.scheduledKnowledgeDirectoryQueryFuture.isDone()) {
+		if (this.scheduledKnowledgeDirectoryQueryFuture != null
+				&& !this.scheduledKnowledgeDirectoryQueryFuture.isDone()) {
 			// There was already a scheduled update, so we don't have to do anything.
-			LOG.debug("It was requested to schedule a query to the Knowledge Directory but there was already a scheduled query! Doing nothing. ");
+			LOG.debug(
+					"It was requested to schedule a query to the Knowledge Directory but there was already a scheduled query! Doing nothing. ");
 			return;
 		}
 
 		var now = new Date();
-		
-		if (knowledgeDirectoryUpdateCooldownEnds == null || knowledgeDirectoryUpdateCooldownEnds.getTime() - now.getTime() < 0) {
+
+		if (knowledgeDirectoryUpdateCooldownEnds == null
+				|| knowledgeDirectoryUpdateCooldownEnds.getTime() - now.getTime() < 0) {
 			// Cooldown already ended: schedule it on the KeRuntime right away.
 			LOG.debug("Scheduling to query the Knowledge Directory right away.");
 			this.scheduledKnowledgeDirectoryQueryFuture = KeRuntime.executorService().schedule(() -> {
@@ -75,7 +78,8 @@ public void scheduleQueryKnowledgeDirectory() {
 			}, 0, TimeUnit.MILLISECONDS);
 		} else {
 			// Cooldown not yet ended: schedule to update when the cooldown ends.
-			LOG.debug("Scheduling to query the Knowledge Directory when the cooldown ends (in {} ms).", knowledgeDirectoryUpdateCooldownEnds.getTime() - now.getTime());
+			LOG.debug("Scheduling to query the Knowledge Directory when the cooldown ends (in {} ms).",
+					knowledgeDirectoryUpdateCooldownEnds.getTime() - now.getTime());
 			this.scheduledKnowledgeDirectoryQueryFuture = KeRuntime.executorService().schedule(() -> {
 				queryKnowledgeDirectory();
 				this.scheduledKnowledgeDirectoryQueryFuture = null;
@@ -87,8 +91,8 @@ private synchronized void queryKnowledgeDirectory() {
 		List<KnowledgeEngineRuntimeConnectionDetails> kerConnectionDetails;
 		try {
 			LOG.info("Querying Knowledge Directory for new peers");
-			kerConnectionDetails = messageDispatcher
-				.getKnowledgeDirectoryConnectionManager().getOtherKnowledgeEngineRuntimeConnectionDetails();
+			kerConnectionDetails = messageDispatcher.getKnowledgeDirectoryConnectionManager()
+					.getOtherKnowledgeEngineRuntimeConnectionDetails();
 			// Check if there are new KERs
 		} catch (Exception e) {
 			LOG.error("Error while querying the Knowledge Directory", e);
@@ -109,16 +113,25 @@ private synchronized void queryKnowledgeDirectory() {
 		for (Iterator<Entry<String, RemoteKerConnection>> it = remoteKerConnections.entrySet().iterator(); it
 				.hasNext();) {
 			Entry<String, RemoteKerConnection> e = it.next();
+
 			if (!kerIds.contains(e.getKey())) {
 				// According the the Knowledge Directory, this KER doesn't exist (anymore)
-				LOG.info("Removing peer that is now gone: " + e.getValue().getRemoteKerDetails().getRuntimeId());
+				KnowledgeEngineRuntimeDetails remoteKerDetails = e.getValue().getRemoteKerDetails();
+				String runtimeId;
+				if (remoteKerDetails == null)
+					runtimeId = "unavailable";
+				else
+					runtimeId = remoteKerDetails.getRuntimeId();
+
+				LOG.info("Removing peer that is now gone: " + runtimeId);
 				e.getValue().stop();
 				it.remove();
 			}
 		}
-		this.knowledgeDirectoryUpdateCooldownEnds = new Date(new Date().getTime() + KNOWLEDGE_DIRECTORY_UPDATE_COOLDOWN * 1000);
+		this.knowledgeDirectoryUpdateCooldownEnds = new Date(
+				new Date().getTime() + KNOWLEDGE_DIRECTORY_UPDATE_COOLDOWN * 1000);
 	}
-	
+
 	public void stop() {
 		this.scheduledScheduleFuture.cancel(false);
 	}

From e2955fa888fd6e4a7f405eec3d6d8cd9eb0927e2 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Thu, 5 Oct 2023 11:58:51 +0200
Subject: [PATCH 05/32] Remove username and password from log file.

---
 .../runtime/messaging/RemoteKerConnection.java        |  5 +++++
 .../runtime/messaging/RemoteKerConnectionManager.java | 11 ++---------
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index 5fe1db89..fcf9ac6f 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -88,6 +88,11 @@ protected PasswordAuthentication getPasswordAuthentication() {
 				.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS).findAndRegisterModules()
 				.setDateFormat(new RFC3339DateFormat());
 	}
+	
+	public URI getRemoteKerUri()
+	{
+		return this.remoteKerUri;
+	}
 
 	private void noError() {
 		this.errorCounter = 0;
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
index 8e7b1003..e46bb2dc 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
@@ -116,14 +116,7 @@ private synchronized void queryKnowledgeDirectory() {
 
 			if (!kerIds.contains(e.getKey())) {
 				// According the the Knowledge Directory, this KER doesn't exist (anymore)
-				KnowledgeEngineRuntimeDetails remoteKerDetails = e.getValue().getRemoteKerDetails();
-				String runtimeId;
-				if (remoteKerDetails == null)
-					runtimeId = "unavailable";
-				else
-					runtimeId = remoteKerDetails.getRuntimeId();
-
-				LOG.info("Removing peer that is now gone: " + runtimeId);
+				LOG.info("Removing peer that is now gone: {}", e.getValue().getRemoteKerUri());
 				e.getValue().stop();
 				it.remove();
 			}
@@ -170,7 +163,7 @@ public Response runtimedetailsPost(KnowledgeEngineRuntimeDetails knowledgeEngine
 		} else {
 			// The KER has changed its details
 			LOG.info("Received new or removed Smart Connectors from peer "
-					+ knowledgeEngineRuntimeDetails.getRuntimeId() + " with "
+					+ remoteKerConnection.getRemoteKerUri() + " with "
 					+ knowledgeEngineRuntimeDetails.getSmartConnectorIds().size() + " smart connectors");
 			remoteKerConnection.updateKerDetails(knowledgeEngineRuntimeDetails);
 		}

From 7949823f546761625232b78945a364645221f878 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Sat, 7 Oct 2023 13:15:34 +0200
Subject: [PATCH 06/32] A working version of the Knowledge Engine for testing
 robustness.

It adds the `Connection: close` header to all inter-KER http requests so
that iptables immediate blocks traffic because a new connection will be
established. Without this header, it will keep working (after blocking
using iptables) because the connection was already established.
---
 examples/unreachable-runtimes/.gitignore      |  1 +
 .../unreachable-runtimes/docker-compose.yml   | 93 +++++++++++++++++++
 examples/unreachable-runtimes/readme.md       | 33 +++++++
 .../smartconnector/runtime/KeRuntime.java     | 19 ++--
 .../messaging/RemoteKerConnection.java        | 33 ++++---
 .../messaging/RemoteKerConnectionManager.java | 16 +++-
 6 files changed, 169 insertions(+), 26 deletions(-)
 create mode 100644 examples/unreachable-runtimes/.gitignore
 create mode 100644 examples/unreachable-runtimes/docker-compose.yml
 create mode 100644 examples/unreachable-runtimes/readme.md

diff --git a/examples/unreachable-runtimes/.gitignore b/examples/unreachable-runtimes/.gitignore
new file mode 100644
index 00000000..d6e830be
--- /dev/null
+++ b/examples/unreachable-runtimes/.gitignore
@@ -0,0 +1 @@
+.python-version
\ No newline at end of file
diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
new file mode 100644
index 00000000..0ed57892
--- /dev/null
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -0,0 +1,93 @@
+services:
+  # This is the knowledge directory, facilitating discovery between different
+  # runtimes. It exposes its service over port 8282.
+  knowledge-directory:
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.1
+
+  # These services are seperate Knowledge Engine runtime, which can host
+  # multiple smart connectors. Note that the REST API port is a DIFFERENT port
+  # number than the ones configured below. It is still the default 8280.
+  runtime-1:
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    environment: 
+      KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
+      KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
+      KD_URL: http://knowledge-directory:8282
+      ENABLE_REASONER: false
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+  runtime-2:
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    environment: 
+      KE_RUNTIME_PORT: 8081
+      KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
+      KD_URL: http://knowledge-directory:8282
+      ENABLE_REASONER: false
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+  runtime-3:
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    cap_add:
+      - NET_ADMIN
+    environment: 
+      KE_RUNTIME_PORT: 8081
+      KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
+      KD_URL: http://knowledge-directory:8282
+      ENABLE_REASONER: false
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+     
+  
+  # These Knowledge Bases use the different runtimes, and exchange data with eachother.
+  kb1:
+    build: ../common/asking_kb
+    environment:
+      KE_URL: http://runtime-1:8280/rest
+      KB_ID: http://example.org/kb1
+      PREFIXES: |
+        {
+          "ex": "http://example.org/"
+        }
+      GRAPH_PATTERN: |
+        ?a ex:relatedTo ?b .
+  kb2:
+    build: ../common/answering_kb
+    environment:
+      KE_URL: http://runtime-2:8280/rest
+      KB_ID: http://example.org/kb2
+      PREFIXES: |
+        {
+          "ex": "http://example.org/"
+        }
+      GRAPH_PATTERN: |
+        ?a ex:relatedTo ?b .
+      KB_DATA: |
+        [
+          {
+            "a": "<http://example.org/Math>",
+            "b": "<http://example.org/Science>"
+          },
+          {
+            "a": "<http://example.org/Books>",
+            "b": "<http://example.org/Magazines>"
+          }
+        ]
+  kb3:
+    build: ../common/answering_kb
+    environment:
+      KE_URL: http://runtime-3:8280/rest
+      KB_ID: http://example.org/kb3
+      PREFIXES: |
+        {
+          "ex": "http://example.org/"
+        }
+      GRAPH_PATTERN: |
+        ?a ex:relatedTo ?b .
+      KB_DATA: |
+        [
+          {
+            "a": "<http://example.org/Music>",
+            "b": "<http://example.org/Songs>"
+          },
+          {
+            "a": "<http://example.org/Red>",
+            "b": "<http://example.org/Blue>"
+          }
+        ]
diff --git a/examples/unreachable-runtimes/readme.md b/examples/unreachable-runtimes/readme.md
new file mode 100644
index 00000000..68f2b11e
--- /dev/null
+++ b/examples/unreachable-runtimes/readme.md
@@ -0,0 +1,33 @@
+## Knowledge Engine's distributed mode test
+This docker compose project is used to test the Knowledge Engine's behavior in distributed mode when something exceptional happens (i.e. divergence from the happy flow). For example, one participant in the Knowledge Network configured its KER incorrectly and therefore it can reach out, but no one can contact the KER from the outside (via the Inter-KER protocol). Under such circumstances, we want the Knowledge Engine to keep functioning and behave as normal as possible.
+
+To test this, we setup a distributed KER environment with 3 KER+KB combis that exchange data. We have `runtime-1+kb1`, `runtime-2+kb2` and `runtime-3+kb3`. By using the `iptables` tool for `runtime-3` we can simulate a misconfigured KER and test how the other Knowledge Engines behave. Use the following instructions to simulate the misconfigured KER.
+
+Start the docker compose project: `docker compose up -d`
+
+Retrieve the internal IP address of the KB3 (because it needs to always be able to contact it `runtime-3` we need its IP to make an exception in `iptables`.
+`docker compose exec kb3 sh`
+`hostname -i`
+
+Make sure runtime-3 is configured to switch between being reachable to being unreachable.
+`docker compose exec runtime-3 bash`
+`apt update -y`
+`apt-get install iptables sudo -y`
+
+Configure `iptables-legacy` to allow the following packets to go through when we block incoming traffic:
+
+```
+iptables-legacy -A INPUT -i lo -j ACCEPT
+iptables-legacy -A INPUT -p tcp -s 172.32.5.6 -j ACCEPT
+iptables-legacy -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
+```
+
+You can quickly test from inside a container whether another container that contains a KER is reachable from there using the following command: `wget -qO- http://runtime-3:8081/runtimedetails`
+
+For example, if `iptables-legacy` is active and blocking all input traffic, you should no longer be able to receive JSON if you go to `runtime-2` and execute a `wget` to `runtime-3`, but you should be able to do the same from `runtime-3` to `runtime-2`.
+
+You can quickly test from inside a container whether another container that contains a KER is reachable from there using the following command: `wget -qO- http://runtime-3:8081/runtimedetails`. You should receive some JSON that looks like:
+ 
+ ```
+ {"runtimeId":"http://runtime-3:8081","smartConnectorIds":["http://example.org/kb3"]}
+ ```
\ No newline at end of file
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/KeRuntime.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/KeRuntime.java
index b92fbb04..f74b9abf 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/KeRuntime.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/KeRuntime.java
@@ -34,8 +34,10 @@ public class KeRuntime {
 
 	static {
 		if (hasConfigProperty(CONF_KEY_MY_EXPOSED_URL) && hasConfigProperty(CONF_KEY_MY_HOSTNAME)) {
-			LOG.error("KE runtime must be configured with {} or {}, not both.", CONF_KEY_MY_EXPOSED_URL, CONF_KEY_MY_HOSTNAME);
-			LOG.info("Using {} allows the use of a reverse proxy for TLS connections, which is recommended.", CONF_KEY_MY_EXPOSED_URL);
+			LOG.error("KE runtime must be configured with {} or {}, not both.", CONF_KEY_MY_EXPOSED_URL,
+					CONF_KEY_MY_HOSTNAME);
+			LOG.info("Using {} allows the use of a reverse proxy for TLS connections, which is recommended.",
+					CONF_KEY_MY_EXPOSED_URL);
 			System.exit(1);
 		}
 
@@ -45,9 +47,13 @@ public class KeRuntime {
 			@Override
 			public Thread newThread(Runnable r) {
 				Thread t = Executors.defaultThreadFactory().newThread(r);
+				t.setUncaughtExceptionHandler((aThread, e) -> {
+					LOG.error("The following uncaught exception should not occur in thread {}.", aThread.getName(), e);
+				});
 				t.setDaemon(true);
 				return t;
 			}
+
 		});
 
 		// Make sure the MessageDispatcher initializes
@@ -76,7 +82,7 @@ public static MessageDispatcher getMessageDispatcher() {
 				} else {
 					var myHostname = getConfigProperty(CONF_KEY_MY_HOSTNAME, "localhost");
 					var myPort = Integer.parseInt(getConfigProperty(CONF_KEY_MY_PORT, "8081"));
-					
+
 					URI myExposedUrl;
 					if (hasConfigProperty(CONF_KEY_MY_EXPOSED_URL)) {
 						myExposedUrl = new URI(getConfigProperty(CONF_KEY_MY_EXPOSED_URL, null));
@@ -86,11 +92,8 @@ public static MessageDispatcher getMessageDispatcher() {
 						myExposedUrl = new URI(EXPOSED_URL_DEFAULT_PROTOCOL + "://" + myHostname + ":" + myPort);
 					}
 
-					messageDispatcher = new MessageDispatcher(
-						myPort,
-						myExposedUrl,
-						new URI(getConfigProperty(CONF_KEY_KD_URL, "http://localhost:8080"))
-					);
+					messageDispatcher = new MessageDispatcher(myPort, myExposedUrl,
+							new URI(getConfigProperty(CONF_KEY_KD_URL, "http://localhost:8080")));
 				}
 			} catch (NumberFormatException | URISyntaxException e) {
 				LOG.error("Could not parse configuration properties, cannot start Knowledge Engine", e);
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index fcf9ac6f..ea6939e0 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -8,10 +8,12 @@
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.http.HttpClient;
+import java.net.http.HttpClient.Version;
 import java.net.http.HttpRequest;
 import java.net.http.HttpRequest.BodyPublishers;
 import java.net.http.HttpResponse;
 import java.net.http.HttpResponse.BodyHandlers;
+import java.time.Duration;
 import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.List;
@@ -113,9 +115,9 @@ private int errorOccurred() {
 	private void updateRemoteKerDataFromPeer() {
 		try {
 			HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-					.header("Content-Type", "application/json").GET().build();
+					.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).GET().build();
 
-			HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+			HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 			if (response.statusCode() == 200) {
 				KnowledgeEngineRuntimeDetails runtimeDetails = objectMapper.readValue(response.body(),
 						KnowledgeEngineRuntimeDetails.class);
@@ -163,13 +165,15 @@ public KnowledgeEngineRuntimeDetails getRemoteKerDetails() {
 
 	private int getWaitTime(int i) {
 		if (i == 1)
-			return 1; // 1
+			return 1;
 		else if (i == 2)
-			return 2; // 5
+			return 2;
 		else if (i == 3)
-			return 5; // 10
-		else
-			return 10; // 15
+			return 5;
+		else if (i == 4)
+			return 10;
+		else 
+			return 15;
 	}
 
 	public List<URI> getRemoteSmartConnectorIds() {
@@ -185,7 +189,7 @@ public List<URI> getRemoteSmartConnectorIds() {
 			}
 		}
 
-		LOG.info("Returning {} SCs for {}.", list.size(), this.remoteKerUri);
+		LOG.debug("Returning {} SCs for {}.", list.size(), this.remoteKerUri);
 
 		return list;
 	}
@@ -218,9 +222,9 @@ public void stop() {
 				HttpRequest request = HttpRequest
 						.newBuilder(new URI(this.remoteKerUri + "/runtimedetails/"
 								+ dispatcher.getKnowledgeDirectoryConnectionManager().getMyKnowledgeDirectoryId()))
-						.header("Content-Type", "application/json").DELETE().build();
+						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).DELETE().build();
 
-				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				if (response.statusCode() == 200) {
 					LOG.trace("Successfully said goodbye to {}", this.remoteKerUri);
 				} else {
@@ -244,9 +248,10 @@ public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOExcept
 				String jsonMessage = objectMapper.writeValueAsString(MessageConverter.toJson(message));
 				HttpRequest request = HttpRequest
 						.newBuilder(new URI(this.remoteKerUri + getPathForMessageType(message)))
-						.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
 
-				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
+				
 				if (response.statusCode() == 202) {
 					this.noError();
 					LOG.trace("Successfully sent message {} to {}", message.getMessageId(), this.remoteKerUri);
@@ -284,9 +289,9 @@ public void sendMyKerDetailsToPeer(KnowledgeEngineRuntimeDetails details) {
 			try {
 				String jsonMessage = objectMapper.writeValueAsString(details);
 				HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-						.header("Content-Type", "application/json").POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
 
-				HttpResponse<String> response = httpClient.send(request, BodyHandlers.ofString());
+				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				if (response.statusCode() == 200) {
 					this.noError();
 					LOG.trace("Successfully sent updated KnowledgeEngineRuntimeDetails to {}", this.remoteKerUri);
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
index e46bb2dc..9ef54287 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnectionManager.java
@@ -53,7 +53,11 @@ public RemoteKerConnectionManager(MessageDispatcher messageDispatcher) {
 	public void start() {
 		// Make a schedule to schedule a knowledge directory update every minute.
 		scheduledScheduleFuture = KeRuntime.executorService().scheduleAtFixedRate(() -> {
-			scheduleQueryKnowledgeDirectory();
+			try {
+				scheduleQueryKnowledgeDirectory();
+			} catch (Throwable t) {
+				LOG.error("", t);
+			}
 		}, 5, KNOWLEDGE_DIRECTORY_UPDATE_INTERVAL, TimeUnit.SECONDS);
 	}
 
@@ -73,13 +77,18 @@ public void scheduleQueryKnowledgeDirectory() {
 			// Cooldown already ended: schedule it on the KeRuntime right away.
 			LOG.debug("Scheduling to query the Knowledge Directory right away.");
 			this.scheduledKnowledgeDirectoryQueryFuture = KeRuntime.executorService().schedule(() -> {
+				try {
 				queryKnowledgeDirectory();
+				} catch (Throwable t) {
+					LOG.error("", t);
+				}
 				this.scheduledKnowledgeDirectoryQueryFuture = null;
 			}, 0, TimeUnit.MILLISECONDS);
 		} else {
 			// Cooldown not yet ended: schedule to update when the cooldown ends.
 			LOG.debug("Scheduling to query the Knowledge Directory when the cooldown ends (in {} ms).",
 					knowledgeDirectoryUpdateCooldownEnds.getTime() - now.getTime());
+
 			this.scheduledKnowledgeDirectoryQueryFuture = KeRuntime.executorService().schedule(() -> {
 				queryKnowledgeDirectory();
 				this.scheduledKnowledgeDirectoryQueryFuture = null;
@@ -162,9 +171,8 @@ public Response runtimedetailsPost(KnowledgeEngineRuntimeDetails knowledgeEngine
 			KeRuntime.executorService().execute(() -> scheduleQueryKnowledgeDirectory());
 		} else {
 			// The KER has changed its details
-			LOG.info("Received new or removed Smart Connectors from peer "
-					+ remoteKerConnection.getRemoteKerUri() + " with "
-					+ knowledgeEngineRuntimeDetails.getSmartConnectorIds().size() + " smart connectors");
+			LOG.info("Received new or removed Smart Connectors from peer " + remoteKerConnection.getRemoteKerUri()
+					+ " with " + knowledgeEngineRuntimeDetails.getSmartConnectorIds().size() + " smart connectors");
 			remoteKerConnection.updateKerDetails(knowledgeEngineRuntimeDetails);
 		}
 		return Response.status(200).build();

From f59256ffe9e5f976d50c9cde2ab9ff940f664ca8 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Sat, 7 Oct 2023 16:48:25 +0200
Subject: [PATCH 07/32] Remove the connection: close header

This header interferes with optimal functioning of the http client and
we do not want that in our code. We can achieve the same using the
jdk.httpclient.keepalive.timeout property set to 1 second.
---
 examples/unreachable-runtimes/Dockerfile             |  4 ++++
 examples/unreachable-runtimes/docker-compose.yml     | 12 ++++++------
 .../runtime/messaging/RemoteKerConnection.java       |  8 ++++----
 3 files changed, 14 insertions(+), 10 deletions(-)
 create mode 100644 examples/unreachable-runtimes/Dockerfile

diff --git a/examples/unreachable-runtimes/Dockerfile b/examples/unreachable-runtimes/Dockerfile
new file mode 100644
index 00000000..2c41b4ca
--- /dev/null
+++ b/examples/unreachable-runtimes/Dockerfile
@@ -0,0 +1,4 @@
+FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+
+RUN apt update -y
+RUN apt-get install iptables sudo -y
diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
index 0ed57892..554a5e52 100644
--- a/examples/unreachable-runtimes/docker-compose.yml
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -8,23 +8,23 @@ services:
   # multiple smart connectors. Note that the REST API port is a DIFFERENT port
   # number than the ones configured below. It is still the default 8280.
   runtime-1:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    build: .
     environment: 
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-2:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    build: .
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-3:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+    build: .
     cap_add:
       - NET_ADMIN
     environment: 
@@ -32,7 +32,7 @@ services:
       KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.allowRestrictedHeaders=Connection"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
      
   
   # These Knowledge Bases use the different runtimes, and exchange data with eachother.
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index ea6939e0..93dc00b2 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -115,7 +115,7 @@ private int errorOccurred() {
 	private void updateRemoteKerDataFromPeer() {
 		try {
 			HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-					.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).GET().build();
+					.header("Content-Type", "application/json").version(Version.HTTP_1_1).GET().build();
 
 			HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 			if (response.statusCode() == 200) {
@@ -222,7 +222,7 @@ public void stop() {
 				HttpRequest request = HttpRequest
 						.newBuilder(new URI(this.remoteKerUri + "/runtimedetails/"
 								+ dispatcher.getKnowledgeDirectoryConnectionManager().getMyKnowledgeDirectoryId()))
-						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).DELETE().build();
+						.header("Content-Type", "application/json").version(Version.HTTP_1_1).DELETE().build();
 
 				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				if (response.statusCode() == 200) {
@@ -248,7 +248,7 @@ public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOExcept
 				String jsonMessage = objectMapper.writeValueAsString(MessageConverter.toJson(message));
 				HttpRequest request = HttpRequest
 						.newBuilder(new URI(this.remoteKerUri + getPathForMessageType(message)))
-						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
 
 				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				
@@ -289,7 +289,7 @@ public void sendMyKerDetailsToPeer(KnowledgeEngineRuntimeDetails details) {
 			try {
 				String jsonMessage = objectMapper.writeValueAsString(details);
 				HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-						.header("Content-Type", "application/json").header("Connection", "close").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
 
 				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				if (response.statusCode() == 200) {

From 8e303d96c0cb76958a80ee60fd215721c659bc65 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Tue, 10 Oct 2023 11:04:06 +0200
Subject: [PATCH 08/32] Improve example.

---
 README.md                                        |  2 +-
 examples/unreachable-runtimes/docker-compose.yml | 11 ++++++++---
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 1071dfcb..22c1ad59 100644
--- a/README.md
+++ b/README.md
@@ -187,7 +187,7 @@ The Knowledge Engine project consists of the following Maven modules:
 - `smart-connector-rest-server`
 	- This module contains the REST API layer that is built on top of the Java Developer API.
 - `smart-connector-rest-dist`
-  - A distribution of the server that provides the REST API layer for your smart connector(s), and uses the smart connector implementation from the `smart-connector` module. For instructions on how to use it, refer to [the section below](#how-to-use-the-rest-api). For instructions on how to set it up, refer to [this section](#how-to-administer-the-rest-api).
+  - A distribution of the server that provides the REST API layer for your smart connector(s), and uses the smart connector implementation from the `smart-connector` module. For instructions on how to use it, refer to [the section below](#using-the-rest-api). For instructions on how to set it up, refer to [this section](#advanced-administering-a-knowledge-engine-runtime).
 - `admin-ui`
 	- A REST API which provides meta-data about smart connectors in a knowledge network. Can be used in an administration inferface for a knowledge network. It is implemented as a knowledge base that uses metadata of other knowledge bases.
 
diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
index 554a5e52..32709b99 100644
--- a/examples/unreachable-runtimes/docker-compose.yml
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -9,20 +9,25 @@ services:
   # number than the ones configured below. It is still the default 8280.
   runtime-1:
     build: .
+    #to allow configuring iptables
+    cap_add:
+      - NET_ADMIN
     environment: 
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-2:
     build: .
+    cap_add:
+      - NET_ADMIN
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-3:
     build: .
     cap_add:
@@ -32,7 +37,7 @@ services:
       KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
      
   
   # These Knowledge Bases use the different runtimes, and exchange data with eachother.

From 1f24d5a0ec66c4ac6c31a40a497e94a8e6b15f4d Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Tue, 10 Oct 2023 16:29:50 +0200
Subject: [PATCH 09/32] Improve docs.

---
 .../unreachable-runtimes/docker-compose.yml   |  6 ++--
 examples/unreachable-runtimes/readme.md       | 34 +++++++++++++------
 2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
index 32709b99..8ee4629e 100644
--- a/examples/unreachable-runtimes/docker-compose.yml
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -17,7 +17,7 @@ services:
       KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-2:
     build: .
     cap_add:
@@ -27,7 +27,7 @@ services:
       KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
   runtime-3:
     build: .
     cap_add:
@@ -37,7 +37,7 @@ services:
       KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
       KD_URL: http://knowledge-directory:8282
       ENABLE_REASONER: false
-      #JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
+      JAVA_TOOL_OPTIONS: "-Djdk.httpclient.keepalive.timeout=1"
      
   
   # These Knowledge Bases use the different runtimes, and exchange data with eachother.
diff --git a/examples/unreachable-runtimes/readme.md b/examples/unreachable-runtimes/readme.md
index 68f2b11e..e5d1fc0f 100644
--- a/examples/unreachable-runtimes/readme.md
+++ b/examples/unreachable-runtimes/readme.md
@@ -5,20 +5,24 @@ To test this, we setup a distributed KER environment with 3 KER+KB combis that e
 
 Start the docker compose project: `docker compose up -d`
 
-Retrieve the internal IP address of the KB3 (because it needs to always be able to contact it `runtime-3` we need its IP to make an exception in `iptables`.
-`docker compose exec kb3 sh`
-`hostname -i`
+Retrieve the internal IP address of the KB3 (because it needs to always be able to contact it `runtime-3` we need its IP to make an exception in `iptables`). This is not really necessary if we use the hostname `kb3` of knowledge base 3 like we do below, but if you use an IP address there you should use the commands below to retrieve this IP. It changes everytime you restart the docker compose project.
 
-Make sure runtime-3 is configured to switch between being reachable to being unreachable.
-`docker compose exec runtime-3 bash`
-`apt update -y`
-`apt-get install iptables sudo -y`
+```
+> docker compose exec kb3 sh
+> hostname -i
+```
+
+Make sure runtime-3 is configured to switch between being reachable to being unreachable. First open a shell for runtime-3.
+
+```
+docker compose exec runtime-3 bash
+```
 
 Configure `iptables-legacy` to allow the following packets to go through when we block incoming traffic:
 
 ```
 iptables-legacy -A INPUT -i lo -j ACCEPT
-iptables-legacy -A INPUT -p tcp -s 172.32.5.6 -j ACCEPT
+iptables-legacy -A INPUT -p tcp -s kb3 -j ACCEPT
 iptables-legacy -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
 ```
 
@@ -28,6 +32,16 @@ For example, if `iptables-legacy` is active and blocking all input traffic, you
 
 You can quickly test from inside a container whether another container that contains a KER is reachable from there using the following command: `wget -qO- http://runtime-3:8081/runtimedetails`. You should receive some JSON that looks like:
  
- ```
+```
  {"runtimeId":"http://runtime-3:8081","smartConnectorIds":["http://example.org/kb3"]}
- ```
\ No newline at end of file
+```
+
+Now, keep an eye on the log file with `docker compose logs -f` and use the following `iptables-legacy` commands to switch between unreachable and reachable.
+
+```
+iptables-legacy -P INPUT DROP
+#runtime-3 is now unreachable for other KERs, but can still reach the Knowledge Directory (KD) and other KERs.
+
+iptables-legacy -P INPUT ACCEPT
+#runtime-3 is now reachable again for other KERs and can also reach the KD and other KERs.
+```
\ No newline at end of file

From 90f75b5e4fc5bd157786aa8280ed8fcb2d3f7d84 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Thu, 12 Oct 2023 09:30:59 +0200
Subject: [PATCH 10/32] Implement a timeout.

We need a timeout after all. Does this interfere with our strive to
support human-in-the-loop and some KBs might take days to answer? I do
not think this interferes, because the timeout is on sending the REST
message and receiving a 200. The timeout for human-in-the-loop is on how
long the SerialMatchingProcessor will wait until it continues with
processing the next matching KI. Here we want to be able to wait
indefinitely.
---
 .../messaging/RemoteKerConnection.java        | 22 ++++++++++++-------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index 93dc00b2..45c7b152 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -43,6 +43,11 @@
  */
 public class RemoteKerConnection {
 
+	/**
+	 * A maximum amount of time to wait for othe HTTP REST call to fail/succeed.
+	 */
+	private static final int HTTP_TIMEOUT = 30;
+
 	public static final Logger LOG = LoggerFactory.getLogger(RemoteKerConnection.class);
 
 	private final KnowledgeEngineRuntimeConnectionDetails remoteKerConnectionDetails;
@@ -84,15 +89,14 @@ protected PasswordAuthentication getPasswordAuthentication() {
 			this.remoteKerUri = kerConnectionDetails.getExposedUrl();
 		}
 
-		this.httpClient = builder.build();
+		this.httpClient = builder.connectTimeout(Duration.ofSeconds(HTTP_TIMEOUT)).build();
 
 		objectMapper = new ObjectMapper().disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
 				.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS).findAndRegisterModules()
 				.setDateFormat(new RFC3339DateFormat());
 	}
-	
-	public URI getRemoteKerUri()
-	{
+
+	public URI getRemoteKerUri() {
 		return this.remoteKerUri;
 	}
 
@@ -172,7 +176,7 @@ else if (i == 3)
 			return 5;
 		else if (i == 4)
 			return 10;
-		else 
+		else
 			return 15;
 	}
 
@@ -248,10 +252,11 @@ public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOExcept
 				String jsonMessage = objectMapper.writeValueAsString(MessageConverter.toJson(message));
 				HttpRequest request = HttpRequest
 						.newBuilder(new URI(this.remoteKerUri + getPathForMessageType(message)))
-						.header("Content-Type", "application/json").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").version(Version.HTTP_1_1)
+						.POST(BodyPublishers.ofString(jsonMessage)).build();
 
 				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
-				
+
 				if (response.statusCode() == 202) {
 					this.noError();
 					LOG.trace("Successfully sent message {} to {}", message.getMessageId(), this.remoteKerUri);
@@ -289,7 +294,8 @@ public void sendMyKerDetailsToPeer(KnowledgeEngineRuntimeDetails details) {
 			try {
 				String jsonMessage = objectMapper.writeValueAsString(details);
 				HttpRequest request = HttpRequest.newBuilder(new URI(this.remoteKerUri + "/runtimedetails"))
-						.header("Content-Type", "application/json").version(Version.HTTP_1_1).POST(BodyPublishers.ofString(jsonMessage)).build();
+						.header("Content-Type", "application/json").version(Version.HTTP_1_1)
+						.POST(BodyPublishers.ofString(jsonMessage)).build();
 
 				HttpResponse<String> response = this.httpClient.send(request, BodyHandlers.ofString());
 				if (response.statusCode() == 200) {

From c024758d74b561be6fca1dbf8420f8dcdb1f0dbd Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Thu, 12 Oct 2023 10:47:31 +0200
Subject: [PATCH 11/32] Use the latest version of the TKE.

---
 examples/unreachable-runtimes/Dockerfile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/unreachable-runtimes/Dockerfile b/examples/unreachable-runtimes/Dockerfile
index 2c41b4ca..c2300f41 100644
--- a/examples/unreachable-runtimes/Dockerfile
+++ b/examples/unreachable-runtimes/Dockerfile
@@ -1,4 +1,4 @@
-FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.2-SNAPSHOT
+FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
 
 RUN apt update -y
 RUN apt-get install iptables sudo -y

From 76d4ce0f3aae0d8fa6070df8f7050e717e05fba9 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 13 Oct 2023 08:45:48 +0200
Subject: [PATCH 12/32] Prepare for release.

---
 README.md                                     | 24 +++++++++----------
 .../src/main/resources/openapi-admin-ui.yaml  |  2 +-
 docs/04_distributed_mode.md                   |  4 ++--
 examples/authentication/docker-compose.yml    |  6 ++---
 examples/multiple-runtimes/docker-compose.yml |  8 +++----
 examples/reasoner/docker-compose.yml          |  2 +-
 examples/rest-api/docker-compose.yml          |  2 +-
 .../unreachable-runtimes/docker-compose.yml   |  2 +-
 pom.xml                                       |  2 +-
 .../src/main/resources/openapi-sc.yaml        |  2 +-
 10 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/README.md b/README.md
index 22c1ad59..f5aab820 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ The easiest way to start a Knowledge Engine runtime is with Docker:
 ```bash
 docker run \
 	-p 8280:8280 \
-	ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+	ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
 ```
 
 The Knowledge Engine runtime is now available to use via the REST API at base URL `http://localhost:8280/rest` on your host machine.
@@ -93,7 +93,7 @@ docker run \
   -p 8081:8081 \
   -e KD_URL=https://knowledge-directory.example.org \
   -e KE_RUNTIME_EXPOSED_URL=https://your-domain.example.org:8081 \
-  ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+  ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
 ```
 
 ### Running with Java
@@ -111,7 +111,7 @@ export KE_RUNTIME_EXPOSED_URL=https://your-domain.example.org:8081
 # Start it. The argument (8280) denotes the port number at which it
 # will listen for connections to the Knowledge Engine REST API.
 java -jar -Dorg.slf4j.simpleLogger.logFile=smart-connector.log \
-  smart-connector-rest-dist-1.2.1-with-dependencies.jar 8280
+  smart-connector-rest-dist-1.2.2-with-dependencies.jar 8280
 ```
 
 The JAR can be retrieved by compiling the project:
@@ -205,17 +205,17 @@ These are instructions on what to do when we release a new version of the knowle
 5. Build and push the new Docker images to GitLab:
 
 ```bash
-docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/smart-connector-rest-dist:1.2.1 --push
-docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/knowledge-directory:1.2.1 --push
-docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/admin-ui:1.2.1 --push
+docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/smart-connector-rest-dist:1.2.2 --push
+docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/knowledge-directory:1.2.2 --push
+docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/admin-ui:1.2.2 --push
 ```
 
 6. Build and push the new Docker images to GitHub:
 
 ```bash
-docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/smart-connector:1.2.1 --push
-docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.1 --push
-docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/admin-ui:1.2.1 --push
+docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/smart-connector:1.2.2 --push
+docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2 --push
+docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/admin-ui:1.2.2 --push
 ```
 
 7. Prepare the next SNAPSHOT version and make a commit for that too.
@@ -232,7 +232,7 @@ docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/
 10. Inform mailing list(s) (and [the blog](https://www.knowledge-engine.eu/blog/)) about the new release.
 
 ## (advanced) Administering a Knowledge Engine runtime
-To start a new instance of the REST API knowledge engine version 1.2.1, make sure you have `git checkout 1.2.1` the tag `1.2.1`. Now make sure you run the `mvn clean install` command successfully from the root of the repository.
+To start a new instance of the REST API knowledge engine version 1.2.2, make sure you have `git checkout 1.2.2` the tag `1.2.2`. Now make sure you run the `mvn clean install` command successfully from the root of the repository.
 
 ### Starting the Knowledge Engine in local mode
 When no additional configuration parameters are provided, the Knowledge Engine will by default run in local mode. This means you can create multiple smart connectors that can communicate with each other through the REST API, but the Knowledge Engine will not connect to a knowledge directory and will not be able to connect with smart connectors running in other runtimes.
@@ -246,13 +246,13 @@ cd smart-connector-rest-dist/target
 Finally, start the server (note that you can configure a log file by including the `-Dorg.slf4j.simpleLogger.logFile=ke.log` system property to the JVM):
 
 ```bash
-java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.1.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
+java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
 ```
 
 If you want to run in it in the background, you can use the `nohup` linux command (which does not use the simpleLogger configuration system property, but redirects the standard err/out):
 
 ```bash
-nohup java -cp "smart-connector-rest-dist-1.2.1.jar:dependency/*" eu.knowledge.engine.rest.Main 8280 > ke.log
+nohup java -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280 > ke.log
 ```
 
 ### Starting the Knowledge Engine in distributed mode
diff --git a/admin-ui/src/main/resources/openapi-admin-ui.yaml b/admin-ui/src/main/resources/openapi-admin-ui.yaml
index 93baa872..0e3e0e12 100644
--- a/admin-ui/src/main/resources/openapi-admin-ui.yaml
+++ b/admin-ui/src/main/resources/openapi-admin-ui.yaml
@@ -5,7 +5,7 @@ info:
   description:
     This API provides information on Knowledge Engine Runtimes (todo), Smart Connectors, Knowledge Bases, and Knowledge
     Interactions in a Knowledge Engine Network.
-  version: 1.0.1-SNAPSHOT
+  version: 1.2.2
   
 paths:
   /rest/admin/sc/all/{include-meta}:
diff --git a/docs/04_distributed_mode.md b/docs/04_distributed_mode.md
index 601bbfb2..604e70c7 100644
--- a/docs/04_distributed_mode.md
+++ b/docs/04_distributed_mode.md
@@ -16,7 +16,7 @@ First of all, you need to start a knowledge directory. The desired port number f
 ```bash
 cd knowledge-directory/target/
 
-java -Dorg.slf4j.simpleLogger.logFile=kd.log -cp "knowledge-directory-1.2.1.jar:dependency/*" eu.knowledge.engine.knowledgedirectory.Main 8080
+java -Dorg.slf4j.simpleLogger.logFile=kd.log -cp "knowledge-directory-1.2.2.jar:dependency/*" eu.knowledge.engine.knowledgedirectory.Main 8080
 ```
 
 The `nohup` command can be used to run the process in the background. On overview of the registered Knowledge Engine runtimes can be found on `http://localhost:8080/ker/` (or another host or port if you desire).
@@ -39,7 +39,7 @@ export KD_URL=http://localhost:8080
 export KE_RUNTIME_EXPOSED_URL=http://localhost:8081
 export KE_RUNTIME_PORT=8081
 
-java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.1.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
+java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
 ```
 
 ### Using Basic Authentication to secure data exchange
diff --git a/examples/authentication/docker-compose.yml b/examples/authentication/docker-compose.yml
index fd49c4d7..75fd046d 100644
--- a/examples/authentication/docker-compose.yml
+++ b/examples/authentication/docker-compose.yml
@@ -9,15 +9,15 @@ services:
     depends_on:
       - knowledge-directory
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.1
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
   runtime-1:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     environment:
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KD_URL: http://thisisausername:thisisapassword@nginx/kd
       KE_RUNTIME_EXPOSED_URL: http://thisisausername:thisisapassword@nginx/ker1
   runtime-2:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     environment:
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KD_URL: http://thisisausername:thisisapassword@nginx/kd
diff --git a/examples/multiple-runtimes/docker-compose.yml b/examples/multiple-runtimes/docker-compose.yml
index dfe7818f..f02a3626 100644
--- a/examples/multiple-runtimes/docker-compose.yml
+++ b/examples/multiple-runtimes/docker-compose.yml
@@ -2,25 +2,25 @@ services:
   # This is the knowledge directory, facilitating discovery between different
   # runtimes. It exposes its service over port 8282.
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.1
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
 
   # These services are seperate Knowledge Engine runtime, which can host
   # multiple smart connectors. Note that the REST API port is a DIFFERENT port
   # number than the ones configured below. It is still the default 8280.
   runtime-1:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     environment: 
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
       KD_URL: http://knowledge-directory:8282
   runtime-2:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
       KD_URL: http://knowledge-directory:8282
   runtime-3:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
diff --git a/examples/reasoner/docker-compose.yml b/examples/reasoner/docker-compose.yml
index c5a23a29..c9bd43e3 100644
--- a/examples/reasoner/docker-compose.yml
+++ b/examples/reasoner/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   knowledge-engine:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
   kb1:
     build: ../common/asking_kb
     environment:
diff --git a/examples/rest-api/docker-compose.yml b/examples/rest-api/docker-compose.yml
index 54743264..483a0c2d 100644
--- a/examples/rest-api/docker-compose.yml
+++ b/examples/rest-api/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   knowledge-engine:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
     healthcheck:
       test: curl -f http://localhost:8280/rest/sc
       interval: 1s
diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
index 8ee4629e..2498873f 100644
--- a/examples/unreachable-runtimes/docker-compose.yml
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -2,7 +2,7 @@ services:
   # This is the knowledge directory, facilitating discovery between different
   # runtimes. It exposes its service over port 8282.
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.1
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
 
   # These services are seperate Knowledge Engine runtime, which can host
   # multiple smart connectors. Note that the REST API port is a DIFFERENT port
diff --git a/pom.xml b/pom.xml
index 174bebd5..7de073f1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -74,7 +74,7 @@
 		<java.version>17</java.version>
 		<maven.compiler.source>17</maven.compiler.source>
 		<maven.compiler.target>17</maven.compiler.target>
-		<revision>1.2.2-SNAPSHOT</revision>
+		<revision>1.2.2</revision>
 	</properties>
 
 	<dependencyManagement>
diff --git a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
index f683791f..e93730f9 100644
--- a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
+++ b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
@@ -7,7 +7,7 @@ info:
     Interactions are (un)registered and data is exchanged. Each Smart Connector
     is coupled with a Knowledge Base Id, so every rest call uses this Knowledge
     Base Id to identify yourself.
-  version: 1.2.2-SNAPSHOT
+  version: 1.2.2
   
 paths:
   /sc:

From 740ca7e3448902914fb8a2c8950bd96f821346d4 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 13 Oct 2023 09:48:40 +0200
Subject: [PATCH 13/32] Prepare snapshot.

---
 pom.xml                                                        | 2 +-
 smart-connector-rest-server/src/main/resources/openapi-sc.yaml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pom.xml b/pom.xml
index 7de073f1..70c66722 100644
--- a/pom.xml
+++ b/pom.xml
@@ -74,7 +74,7 @@
 		<java.version>17</java.version>
 		<maven.compiler.source>17</maven.compiler.source>
 		<maven.compiler.target>17</maven.compiler.target>
-		<revision>1.2.2</revision>
+		<revision>1.2.3-SNAPSHOT</revision>
 	</properties>
 
 	<dependencyManagement>
diff --git a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
index e93730f9..97a04814 100644
--- a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
+++ b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
@@ -7,7 +7,7 @@ info:
     Interactions are (un)registered and data is exchanged. Each Smart Connector
     is coupled with a Knowledge Base Id, so every rest call uses this Knowledge
     Base Id to identify yourself.
-  version: 1.2.2
+  version: 1.2.3-SNAPSHOT
   
 paths:
   /sc:

From 7273599f1459cdc4341b15ace15f7d388e56be34 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 13 Oct 2023 10:26:10 +0200
Subject: [PATCH 14/32] Forgot to update tag to 1.2.2.

After updating, the unreachable example works as expected. This is too
small of an error to justify another release. Just remember that the
example does not work in tag 1.2.2
---
 examples/unreachable-runtimes/Dockerfile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/examples/unreachable-runtimes/Dockerfile b/examples/unreachable-runtimes/Dockerfile
index c2300f41..108fd9a3 100644
--- a/examples/unreachable-runtimes/Dockerfile
+++ b/examples/unreachable-runtimes/Dockerfile
@@ -1,4 +1,4 @@
-FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.1
+FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
 
 RUN apt update -y
 RUN apt-get install iptables sudo -y

From d3a3c3e0108fd19e6445873a39205f7bcfeb52c6 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 10 Nov 2023 13:05:36 +0100
Subject: [PATCH 15/32] Refactored tests to use KnowledgeNetwork

---
 .../smartconnector/api/TestAskAnswer.java     |  62 ++------
 .../smartconnector/api/TestPostReact.java     | 142 +++++++-----------
 2 files changed, 69 insertions(+), 135 deletions(-)

diff --git a/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestAskAnswer.java b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestAskAnswer.java
index 13711649..a04a1ffe 100644
--- a/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestAskAnswer.java
+++ b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestAskAnswer.java
@@ -11,9 +11,7 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.concurrent.BrokenBarrierException;
-import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
 import org.apache.jena.rdf.model.Resource;
@@ -25,16 +23,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import eu.knowledge.engine.smartconnector.api.AnswerHandler;
-import eu.knowledge.engine.smartconnector.api.AnswerKnowledgeInteraction;
-import eu.knowledge.engine.smartconnector.api.AskKnowledgeInteraction;
-import eu.knowledge.engine.smartconnector.api.AskResult;
-import eu.knowledge.engine.smartconnector.api.Binding;
-import eu.knowledge.engine.smartconnector.api.BindingSet;
-import eu.knowledge.engine.smartconnector.api.CommunicativeAct;
-import eu.knowledge.engine.smartconnector.api.GraphPattern;
-import eu.knowledge.engine.smartconnector.api.SmartConnector;
-import eu.knowledge.engine.smartconnector.api.Vocab;
+import eu.knowledge.engine.smartconnector.util.KnowledgeNetwork;
 import eu.knowledge.engine.smartconnector.util.MockedKnowledgeBase;
 
 public class TestAskAnswer {
@@ -55,23 +44,20 @@ public void testAskAnswer() throws InterruptedException {
 		prefixes.setNsPrefixes(PrefixMapping.Standard);
 		prefixes.setNsPrefix("ex", "https://www.tno.nl/example/");
 
-		int wait = 2;
-		final CountDownLatch kb2ReceivedData = new CountDownLatch(1);
+		var kn = new KnowledgeNetwork();
+		kb1 = new MockedKnowledgeBase("kb1");
+		kn.addKB(kb1);
+		kb2 = new MockedKnowledgeBase("kb2");
+		kn.addKB(kb2);
 
-		kb1 = new MockedKnowledgeBase("kb1") {
-			@Override
-			public void smartConnectorReady(SmartConnector aSC) {
-				LOG.info("smartConnector of {} ready.", this.name);
-			}
-		};
+		LOG.info("Waiting for ready...");
 
 		GraphPattern gp1 = new GraphPattern(prefixes, "?a <https://www.tno.nl/example/b> ?c.");
 
-		CommunicativeAct act1 = new CommunicativeAct(new HashSet<Resource>(Arrays.asList(Vocab.INFORM_PURPOSE)),
-				new HashSet<Resource>(Arrays.asList(Vocab.RETRIEVE_KNOWLEDGE_PURPOSE)));
+		CommunicativeAct act1 = new CommunicativeAct(new HashSet<>(Arrays.asList(Vocab.INFORM_PURPOSE)),
+				new HashSet<>(Arrays.asList(Vocab.RETRIEVE_KNOWLEDGE_PURPOSE)));
 		AnswerKnowledgeInteraction aKI = new AnswerKnowledgeInteraction(act1, gp1);
-		kb1.register(aKI, (AnswerHandler) (anAKI, anAnswerExchangeInfo) -> {
-			var aBindingSet = anAnswerExchangeInfo.getIncomingBindings();
+		kb1.register(aKI, (anAKI, anAnswerExchangeInfo) -> {
 			assertTrue(
 					anAnswerExchangeInfo.getIncomingBindings().isEmpty()
 							|| anAnswerExchangeInfo.getIncomingBindings().iterator().next().getVariables().isEmpty(),
@@ -85,28 +71,17 @@ public void smartConnectorReady(SmartConnector aSC) {
 
 			return bindingSet;
 		});
-		kb1.start();
-		kb1.syncKIs();
-		Thread.sleep(5000);
+		LOG.info("Registered first AKI");
 
-		kb2 = new MockedKnowledgeBase("kb2") {
-			@Override
-			public void smartConnectorReady(SmartConnector aSC) {
-				LOG.info("smartConnector of {} ready.", this.name);
-
-			}
-		};
 
 		GraphPattern gp2 = new GraphPattern(prefixes, "?x <https://www.tno.nl/example/b> ?y.");
-		CommunicativeAct act2 = new CommunicativeAct(new HashSet<Resource>(Arrays.asList(Vocab.INFORM_PURPOSE)),
-				new HashSet<Resource>(Arrays.asList(Vocab.RETRIEVE_KNOWLEDGE_PURPOSE)));
+		CommunicativeAct act2 = new CommunicativeAct(new HashSet<>(Arrays.asList(Vocab.INFORM_PURPOSE)),
+				new HashSet<>(Arrays.asList(Vocab.RETRIEVE_KNOWLEDGE_PURPOSE)));
 		AskKnowledgeInteraction askKI = new AskKnowledgeInteraction(act2, gp2);
 		kb2.register(askKI);
-
-		kb2.start();
-		kb2.syncKIs();
-		LOG.trace("After kb2 register");
-		Thread.sleep(10000);
+		LOG.info("Registered second AKI");
+		kn.sync();
+		LOG.info("Synced knowledge network");
 
 		BindingSet bindings = null;
 		try {
@@ -134,11 +109,6 @@ public void smartConnectorReady(SmartConnector aSC) {
 		assertEquals("<https://www.tno.nl/example/c>", b.get("y"), "Binding of 'y' is incorrect.");
 
 		assertFalse(iter.hasNext(), "This BindingSet should only have a single binding.");
-		kb2ReceivedData.countDown();
-
-		assertTrue(kb2ReceivedData.await(wait, TimeUnit.SECONDS),
-				"KB2 should have initialized within " + wait + " seconds.");
-
 	}
 
 	@AfterAll
diff --git a/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestPostReact.java b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestPostReact.java
index 85a243c6..81e98c7a 100644
--- a/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestPostReact.java
+++ b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestPostReact.java
@@ -6,8 +6,7 @@
 import static org.junit.jupiter.api.Assertions.fail;
 
 import java.util.Iterator;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.ExecutionException;
 
 import org.apache.jena.shared.PrefixMapping;
 import org.apache.jena.sparql.graph.PrefixMappingMem;
@@ -16,21 +15,15 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import eu.knowledge.engine.smartconnector.api.Binding;
-import eu.knowledge.engine.smartconnector.api.BindingSet;
-import eu.knowledge.engine.smartconnector.api.CommunicativeAct;
-import eu.knowledge.engine.smartconnector.api.GraphPattern;
-import eu.knowledge.engine.smartconnector.api.PostKnowledgeInteraction;
-import eu.knowledge.engine.smartconnector.api.PostResult;
-import eu.knowledge.engine.smartconnector.api.ReactHandler;
-import eu.knowledge.engine.smartconnector.api.ReactKnowledgeInteraction;
-import eu.knowledge.engine.smartconnector.api.SmartConnector;
+import eu.knowledge.engine.smartconnector.util.KnowledgeNetwork;
 import eu.knowledge.engine.smartconnector.util.MockedKnowledgeBase;
 
 public class TestPostReact {
 	private static MockedKnowledgeBase kb1;
 	private static MockedKnowledgeBase kb2;
 
+	public boolean kb2Received = false;
+
 	private static final Logger LOG = LoggerFactory.getLogger(TestPostReact.class);
 
 	@Test
@@ -39,85 +32,56 @@ public void testPostReact() throws InterruptedException {
 		prefixes.setNsPrefixes(PrefixMapping.Standard);
 		prefixes.setNsPrefix("ex", "https://www.tno.nl/example/");
 
-		int wait = 15;
-		final CountDownLatch kb2Initialized = new CountDownLatch(1);
-		final CountDownLatch kb2ReceivedKnowledge = new CountDownLatch(1);
-		final CountDownLatch kb1ReceivedPostResult = new CountDownLatch(1);
-
-		kb1 = new MockedKnowledgeBase("kb1") {
-			private PostKnowledgeInteraction ki;
-
-			@Override
-			public void smartConnectorReady(SmartConnector aSC) {
-				GraphPattern gp = new GraphPattern(prefixes, "?a <https://www.tno.nl/example/b> ?c.");
-				this.ki = new PostKnowledgeInteraction(new CommunicativeAct(), gp, null);
-				aSC.register(this.ki);
-
-				this.waitForOtherKbAndPostSomething();
-			}
-
-			private void waitForOtherKbAndPostSomething() {
-				// Wait until KB2 completed its latch.
-				try {
-					assertTrue(kb2Initialized.await(wait, TimeUnit.SECONDS),
-							"kb2 should have been initialized within " + wait + " seconds.");
-				} catch (InterruptedException e) {
-					fail("Should not throw any exception.");
-				}
-
-				BindingSet bindingSet = new BindingSet();
-				Binding binding = new Binding();
-				binding.put("a", "<https://www.tno.nl/example/a>");
-				binding.put("c", "<https://www.tno.nl/example/c>");
-				bindingSet.add(binding);
-
-				try {
-					Thread.sleep(4000); // we wait with posting until all Smart Connectors are up-to-date.
-					PostResult result = this.post(this.ki, bindingSet).get();
-					LOG.info("After post!");
-					kb1ReceivedPostResult.countDown();
-				} catch (Exception e) {
-					LOG.error("Erorr", e);
-				}
-			}
-		};
-		kb1.start();
-
-		kb2 = new MockedKnowledgeBase("kb2") {
-			@Override
-			public void smartConnectorReady(SmartConnector aSC) {
-
-				GraphPattern gp = new GraphPattern(prefixes, "?d <https://www.tno.nl/example/b> ?e.");
-				ReactKnowledgeInteraction ki = new ReactKnowledgeInteraction(new CommunicativeAct(), gp, null);
-
-				aSC.register(ki, (ReactHandler) (anRKI, aReactExchangeInfo) -> {
-					LOG.trace("Reacting...");
-					var argument = aReactExchangeInfo.getArgumentBindings();
-
-					Iterator<Binding> iter = argument.iterator();
-					Binding b = iter.next();
-
-					assertEquals("<https://www.tno.nl/example/a>", b.get("d"), "Binding of 'd' is incorrect.");
-					assertEquals("<https://www.tno.nl/example/c>", b.get("e"), "Binding of 'e' is incorrect.");
-
-					assertFalse(iter.hasNext(), "This BindingSet should only have a single binding.");
-
-					// Complete the latch to make the test pass.
-					kb2ReceivedKnowledge.countDown();
-
-					return new BindingSet();
-				});
-				kb2Initialized.countDown();
-			}
-		};
-		kb2.start();
-
-		assertTrue(kb2ReceivedKnowledge.await(wait, TimeUnit.SECONDS),
-				"KB2 should receive knowledge within " + wait + " seconds.");
-
-		assertTrue(kb1ReceivedPostResult.await(wait, TimeUnit.SECONDS),
-				"KB1 should receive PostResult within " + wait + " seconds.");
+		KnowledgeNetwork kn = new KnowledgeNetwork();
+		kb1 = new MockedKnowledgeBase("kb1");
+		kn.addKB(kb1);
+		kb2 = new MockedKnowledgeBase("kb2");
+		kn.addKB(kb2);
+
+		GraphPattern gp1 = new GraphPattern(prefixes, "?a <https://www.tno.nl/example/b> ?c.");
+		PostKnowledgeInteraction pKI = new PostKnowledgeInteraction(new CommunicativeAct(), gp1, null);
+		kb1.register(pKI);
+
+		GraphPattern gp2 = new GraphPattern(prefixes, "?d <https://www.tno.nl/example/b> ?e.");
+		ReactKnowledgeInteraction rKI = new ReactKnowledgeInteraction(new CommunicativeAct(), gp2, null);
+		kb2.register(rKI, ((anRKI, aReactExchangeInfo) -> {
+			LOG.trace("KB2 reacting...");
+			TestPostReact.this.kb2Received = true;
+			var argument = aReactExchangeInfo.getArgumentBindings();
+			Iterator<Binding> iter = argument.iterator();
+			assertTrue(iter.hasNext(), "There should be at least a single binding.");
+			Binding b = iter.next();
+
+			assertEquals("<https://www.tno.nl/example/a>", b.get("d"), "Binding of 'd' is incorrect.");
+			assertEquals("<https://www.tno.nl/example/c>", b.get("e"), "Binding of 'e' is incorrect.");
+
+			assertFalse(iter.hasNext(), "This BindingSet should only have a single binding.");
+
+			return new BindingSet();
+		}));
+
+		kn.sync();
+		LOG.info("Everyone is up-to-date!");
 
+
+		BindingSet bindingSet = new BindingSet();
+		Binding binding = new Binding();
+		binding.put("a", "<https://www.tno.nl/example/a>");
+		binding.put("c", "<https://www.tno.nl/example/c>");
+		bindingSet.add(binding);
+
+		try {
+			PostResult result = kb1.post(pKI, bindingSet).get();
+
+			assertTrue(this.kb2Received, "KB2 should have received the posted data.");
+
+			BindingSet bs = result.getBindings();
+			assertTrue(bs.isEmpty());
+
+			LOG.info("After post!");
+		} catch (ExecutionException e) {
+			LOG.error("Error", e);
+		}
 	}
 
 	@AfterAll

From b366770b8f9db8ff9469209db290622cf50d34a1 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Tue, 28 Nov 2023 21:28:24 +0100
Subject: [PATCH 16/32] Add max capacity on maps to prevent memory leaks.

Done:
- Two maps in MessageRouterImpl now remove (and cancel) oldest entry
when max capacity has been reached.
- beingProcessed in RestKnowledgeBase now also removes) and cancels)
oldest eentry when max capacity has been reached.
- Improve error handling of SerialMatchingProcessor when max capacity
has been reached.

The RestKnowledgeBase max capacity is much lower than that of the
MessageRouterImpl, because we expect the RestKnowledgeBase to correctly
deal with too many handle request (and this prevents the
messageRouterImpl maps to reach max capacity).
---
 .../engine/rest/api/TestPostMemoryLeak.java   | 180 ++++++++++++++++++
 .../rest/api/impl/RestKnowledgeBase.java      |  28 ++-
 .../impl/MessageRouterImpl.java               |  65 ++++---
 .../impl/SerialMatchingProcessor.java         |  36 +++-
 4 files changed, 282 insertions(+), 27 deletions(-)
 create mode 100644 smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java

diff --git a/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java
new file mode 100644
index 00000000..5e9d03a4
--- /dev/null
+++ b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java
@@ -0,0 +1,180 @@
+package eu.knowledge.engine.rest.api;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+
+import eu.knowledge.engine.rest.RestServerHelper;
+import eu.knowledge.engine.test_utils.AsyncTester;
+import eu.knowledge.engine.test_utils.HttpTester;
+import jakarta.json.Json;
+import jakarta.json.JsonObject;
+import jakarta.json.JsonObjectBuilder;
+import jakarta.json.JsonReader;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+public class TestPostMemoryLeak {
+	private static final int SLEEPTIME = 10;
+	private final RestServerHelper rsh = new RestServerHelper();
+	private static int PORT = 8280;
+	private URL url;
+
+	@BeforeAll
+	public void setUpServer() throws InterruptedException {
+		rsh.start(PORT);
+	}
+
+	@Test
+	public void testManyPosts() throws IOException, InterruptedException {
+		url = new URL("http://localhost:" + PORT + "/rest/sc");
+
+		final var reactKBReady = new CountDownLatch(1);
+
+		String kb2Id = "http://example.org/kb2";
+
+		var reactingSc = new AsyncTester(new Runnable() {
+			@Override
+			public void run() {
+
+				String kiId = "http://example.org/kb2/interaction/reactki";
+
+				try {
+					new HttpTester(url, "POST",
+							"{\"knowledgeBaseId\": \"" + kb2Id
+									+ "\", \"knowledgeBaseName\": \"KB2\", \"knowledgeBaseDescription\": \"KB2\"}",
+							Map.of("Content-Type", "application/json", "Accept", "*/*")).expectStatus(200);
+
+					HttpTester registerKi = new HttpTester(new URL(url.toString() + "/ki"), "POST", """
+								{
+								  "knowledgeInteractionType": "ReactKnowledgeInteraction",
+								  "knowledgeInteractionName": "reactki",
+								  "argumentGraphPattern": "?a rdf:type ex:Something .",
+								  "prefixes": {
+								    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+								    "ex": "http://example.org/"
+								  }
+								}
+							""",
+							Map.of("Knowledge-Base-Id", kb2Id, "Content-Type", "application/json", "Accept", "*/*"));
+
+					registerKi.expectStatus(200);
+
+					reactKBReady.countDown();
+
+					while (true) {
+						var test = new HttpTester(new URL(url.toString() + "/handle"), "GET", null, Map
+								.of("Knowledge-Base-Id", kb2Id, "Content-Type", "application/json", "Accept", "*/*"));
+						test.expectStatus(200);
+//						System.out.println("Body: " + test.getBody());
+
+						if (false) {
+							JsonReader jp = Json.createReader(new StringReader(test.getBody()));
+							JsonObject jo = jp.readObject();
+							int handleRequestId = jo.getInt("handleRequestId");
+							JsonObjectBuilder builder = Json.createObjectBuilder();
+
+							builder.add("handleRequestId", handleRequestId);
+							builder.add("bindingSet", JsonObject.EMPTY_JSON_ARRAY);
+							JsonObject jo2 = builder.build();
+
+							String body = jo2.toString();
+
+							System.out.println("Body2: " + body);
+
+							var test2 = new HttpTester(new URL(url.toString() + "/handle"), "POST", body,
+									Map.of("Knowledge-Base-Id", kb2Id, "Knowledge-Interaction-Id", kiId, "Content-Type",
+											"application/json", "Accept", "*/*"));
+							test2.expectStatus(200);
+						}
+						try {
+							Thread.sleep(SLEEPTIME);
+						} catch (InterruptedException e) {
+							fail();
+						}
+					}
+				} catch (MalformedURLException e) {
+					fail();
+				}
+			}
+		});
+		reactingSc.start();
+
+		String kb1Id = "http://example.org/kb1";
+		String kiId = "http://example.org/kb1/interaction/postki";
+
+		new HttpTester(url, "POST",
+				"{\"knowledgeBaseId\": \"" + kb1Id
+						+ "\", \"knowledgeBaseName\": \"KB1\", \"knowledgeBaseDescription\": \"KB1\"}",
+				Map.of("Content-Type", "application/json", "Accept", "*/*")).expectStatus(200);
+
+		HttpTester registerKi = new HttpTester(new URL(url.toString() + "/ki"), "POST", """
+					{
+					  "knowledgeInteractionType": "PostKnowledgeInteraction",
+					  "knowledgeInteractionName": "postki",
+					  "argumentGraphPattern": "?a rdf:type ex:Something .",
+					  "prefixes": {
+					    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+					    "ex": "http://example.org/"
+					  }
+					}
+				""", Map.of("Knowledge-Base-Id", kb1Id, "Content-Type", "application/json", "Accept", "*/*"));
+
+		registerKi.expectStatus(200);
+		reactKBReady.await();
+
+		int counter = 0;
+
+		while (true) {
+			counter++;
+			Thread.sleep(SLEEPTIME);
+			System.out.println("post data");
+			new AsyncTester(new Runnable() {
+				@Override
+				public void run() {
+					try {
+
+						var test = new HttpTester(new URL(TestPostMemoryLeak.this.url.toString() + "/post"), "POST", """
+									[
+									  {
+									    "a": "<http://www.tno.nl/s1>"
+									  },
+									  {
+									    "a": "<http://www.tno.nl/s2>"
+									  }
+									]
+								""", Map.of("Content-Type", "application/json", "Accept", "*/*", "Knowledge-Base-Id",
+								kb1Id, "Knowledge-Interaction-Id", kiId));
+						test.expectStatus(200);
+						System.out.println("finshed posting: " + test.getBody());
+					} catch (MalformedURLException e) {
+						fail();
+					}
+
+				}
+			}).start();
+//			if (counter > 5000)
+//				break;
+		}
+
+		// Start both threads
+//		postingSc.start();
+
+//		postingSc.joinAndRethrow();
+
+	}
+
+	@AfterAll
+	public void cleanUp() {
+		rsh.cleanUp();
+	}
+}
diff --git a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
index c09c4244..a4a1835e 100644
--- a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
+++ b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
@@ -3,9 +3,11 @@
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Queue;
@@ -199,7 +201,31 @@ public RestKnowledgeBase(eu.knowledge.engine.rest.model.SmartConnector scModel,
 		this.knowledgeBaseDescription = scModel.getKnowledgeBaseDescription();
 		this.knowledgeInteractions = new HashMap<>();
 		this.toBeProcessedHandleRequests = new ArrayBlockingQueue<>(QUEUE_SIZE);
-		this.beingProcessedHandleRequests = new ConcurrentHashMap<Integer, HandleRequest>();
+
+		// use a mapping with a maximum capacity and removing the oldest one if new
+		// entries come in when the max capacity is reached. When a KB accepts many
+		// handle requests, but fails to respond to many of them, this causes a memory
+		// leak. With the following code we basically say that a KB is only allowed to
+		// have 100 parallel handle requests outstanding.
+		this.beingProcessedHandleRequests = Collections.synchronizedMap(new LinkedHashMap<Integer, HandleRequest>() {
+			private static final long serialVersionUID = 1L;
+			private static final int MAX_ENTRIES = 100;
+
+			@Override
+			protected boolean removeEldestEntry(Map.Entry<Integer, HandleRequest> eldest) {
+				if (size() > MAX_ENTRIES) {
+					eldest.getValue().getFuture()
+							.completeExceptionally(new KnowledgeEngineException(new Exception("Knowledge base "
+									+ RestKnowledgeBase.this.knowledgeBaseId + " should have max " + MAX_ENTRIES
+									+ " outstanding handle requests. Cancelling oldest handle request "
+									+ eldest.getValue().getHandleRequestId() + ".")));
+					return true;
+				} else {
+					return false;
+				}
+			}
+		});
+
 		this.handleRequestId = new AtomicInteger(0);
 		this.onReady = onReady;
 		this.leaseRenewalTime = scModel.getLeaseRenewalTime();
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
index ac55f8c4..a63ec497 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/MessageRouterImpl.java
@@ -2,6 +2,8 @@
 
 import java.io.IOException;
 import java.net.URI;
+import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
@@ -21,13 +23,48 @@ public class MessageRouterImpl implements MessageRouter, SmartConnectorEndpoint
 
 	private final Logger LOG;
 
+	/**
+	 * In principle the open ask/post messages mappings should not have a max
+	 * capacity, but to prevent memory leaks we cap them at the number below.
+	 */
+	private static final int MAX_ENTRIES = 5000;
+
 	private final SmartConnectorImpl smartConnector;
-	private final Map<UUID, CompletableFuture<AnswerMessage>> openAskMessages = new ConcurrentHashMap<>();
-	private final Map<UUID, CompletableFuture<ReactMessage>> openPostMessages = new ConcurrentHashMap<>();
+	private final Map<UUID, CompletableFuture<AnswerMessage>> openAskMessages = Collections
+			.synchronizedMap(new LinkedHashMap<UUID, CompletableFuture<AnswerMessage>>() {
+				private static final long serialVersionUID = 1L;
+
+				@Override
+				protected boolean removeEldestEntry(Map.Entry<UUID, CompletableFuture<AnswerMessage>> eldest) {
+					if (size() > MAX_ENTRIES) {
+						eldest.getValue().completeExceptionally(new Exception("There should not be " + MAX_ENTRIES
+								+ " open AskMessages. Oldest message with id " + eldest.getKey() + " removed."));
+						return true;
+					} else {
+						return false;
+					}
+				}
+			});
+	private final Map<UUID, CompletableFuture<ReactMessage>> openPostMessages = Collections
+			.synchronizedMap(new LinkedHashMap<UUID, CompletableFuture<ReactMessage>>() {
+				private static final long serialVersionUID = 1L;
+
+				@Override
+				protected boolean removeEldestEntry(Map.Entry<UUID, CompletableFuture<ReactMessage>> eldest) {
+					if (size() > MAX_ENTRIES) {
+						eldest.getValue().completeExceptionally(new Exception("There should not be " + MAX_ENTRIES
+								+ " open PostMessages. Oldest message with id " + eldest.getKey() + " removed."));
+						return true;
+					} else {
+						return false;
+					}
+				}
+			});
 
 	private MessageDispatcherEndpoint messageDispatcherEndpoint = null;
-	
-	//TODO remove metaknowledgebase if it is no longer needed (since the interaction processor is now fully responsible for message handling).
+
+	// TODO remove metaknowledgebase if it is no longer needed (since the
+	// interaction processor is now fully responsible for message handling).
 	private MetaKnowledgeBase metaKnowledgeBase;
 	private InteractionProcessor interactionProcessor;
 
@@ -52,15 +89,7 @@ public CompletableFuture<AnswerMessage> sendAskMessage(AskMessage askMessage) th
 
 		LOG.debug("Sent AskMessage: {}", askMessage);
 
-		return future.handle((r, e) -> {
-
-			if (r == null) {
-				LOG.error("An exception has occured while sending Ask Message ", e);
-				return null;
-			} else {
-				return r;
-			}
-		});
+		return future;
 	}
 
 	@Override
@@ -74,15 +103,7 @@ public CompletableFuture<ReactMessage> sendPostMessage(PostMessage postMessage)
 		messageDispatcher.send(postMessage);
 		LOG.debug("Sent PostMessage: {}", postMessage);
 
-		return future.handle((r, e) -> {
-
-			if (r == null) {
-				LOG.error("An exception has occured while sending Post Message ", e);
-				return null;
-			} else {
-				return r;
-			}
-		});
+		return future;
 	}
 
 	/**
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
index 45162b92..9e5d20e7 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
@@ -118,6 +118,18 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 						try {
 							this.answerMessageFuture = this.messageRouter.sendAskMessage(askMessage);
 							this.previousSend = Instant.now();
+							
+							answerMessageFuture.exceptionally(e -> {
+								this.LOG.warn("Error '{}' occurred while waiting for response to: {}",
+										e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
+										askMessage);
+								this.LOG.debug("", e);
+
+								// continue with the work, otherwise this process will come to a halt.
+								this.checkOtherKnowledgeInteraction(bindingSet);
+								return null;
+							});
+							
 							this.answerMessageFuture.thenAccept(aMessage -> {
 								try {
 									this.answerMessageFuture = null;
@@ -137,7 +149,8 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 								}
 							});
 						} catch (IOException e) {
-							this.LOG.warn("Error '{}' occurred while sending and processing: {}", e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), askMessage);
+							this.LOG.warn("Error '{}' occurred while sending: {}",
+									e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), askMessage);
 							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.
@@ -152,7 +165,8 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 
 					PostKnowledgeInteraction pKI = (PostKnowledgeInteraction) this.myKnowledgeInteraction
 							.getKnowledgeInteraction();
-					if (this.matches(pKI.getArgument(), rKI.getArgument()) && this.matches(pKI.getResult(), rKI.getResult())) {
+					if (this.matches(pKI.getArgument(), rKI.getArgument())
+							&& this.matches(pKI.getResult(), rKI.getResult())) {
 
 						BindingSet transformedArgBindingSet = GraphPatternMatcher.transformBindingSet(pKI.getArgument(),
 								rKI.getArgument(), bindingSet);
@@ -163,6 +177,18 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 						try {
 							this.reactMessageFuture = this.messageRouter.sendPostMessage(postMessage);
 							this.previousSend = Instant.now();
+
+							reactMessageFuture.exceptionally(e -> {
+								this.LOG.warn("Error '{}' occurred while waiting for response to: {}",
+										e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
+										postMessage);
+								this.LOG.debug("", e);
+
+								// continue with the work, otherwise this process will come to a halt.
+								this.checkOtherKnowledgeInteraction(bindingSet);
+								return null;
+							});
+
 							this.reactMessageFuture.thenAccept(aMessage -> {
 								try {
 									this.reactMessageFuture = null;
@@ -187,8 +213,10 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 								}
 							});
 						} catch (IOException e) {
-							
-							this.LOG.warn("Error '{}' occurred while sending and processing: {}", e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), postMessage);
+
+							this.LOG.warn("Error '{}' occurred while sending: {}",
+									e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
+									postMessage);
 							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.

From 69fcc4d3f60c0a27e9c143cef84d445f7cb69d20 Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Wed, 29 Nov 2023 11:27:37 +0100
Subject: [PATCH 17/32] Disable the memory leak test.

---
 .../java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java
index 5e9d03a4..b3e88b25 100644
--- a/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java
+++ b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestPostMemoryLeak.java
@@ -11,6 +11,7 @@
 
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 
@@ -23,6 +24,7 @@
 import jakarta.json.JsonReader;
 
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
+@Disabled
 public class TestPostMemoryLeak {
 	private static final int SLEEPTIME = 10;
 	private final RestServerHelper rsh = new RestServerHelper();
@@ -77,7 +79,7 @@ public void run() {
 						test.expectStatus(200);
 //						System.out.println("Body: " + test.getBody());
 
-						if (false) {
+						if (Math.random() > 0.95) {
 							JsonReader jp = Json.createReader(new StringReader(test.getBody()));
 							JsonObject jo = jp.readObject();
 							int handleRequestId = jo.getInt("handleRequestId");

From 67130cb5bb243209a560b25325d4089f7ac2ea10 Mon Sep 17 00:00:00 2001
From: lathouwerssam <sophie.lathouwers@tno.nl>
Date: Thu, 30 Nov 2023 14:42:17 +0100
Subject: [PATCH 18/32] Removed notifies & resetting of remoteKerDetails

---
 .../runtime/messaging/RemoteKerConnection.java        | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index 45c7b152..af72148b 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -236,7 +236,8 @@ public void stop() {
 							response.statusCode(), response.body());
 				}
 			} catch (IOException | URISyntaxException | InterruptedException e) {
-				LOG.warn("Failed to say goodby to " + remoteKerConnectionDetails.getId(), e);
+				LOG.warn("Failed to say goodbye to " + remoteKerConnectionDetails.getId());
+				LOG.debug("", e);
 			}
 		} else
 			LOG.info("Still ignoring KER {}.", this.remoteKerUri);
@@ -261,31 +262,25 @@ public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOExcept
 					this.noError();
 					LOG.trace("Successfully sent message {} to {}", message.getMessageId(), this.remoteKerUri);
 				} else {
-					this.remoteKerDetails = null;
 					int time = this.errorOccurred();
 					LOG.warn("Ignoring KER {} for {} minutes. Failed to send message {} to {}, got response {}: {}",
 							this.remoteKerUri, time, message.getMessageId(), this.remoteKerUri, response.statusCode(),
 							response.body());
-					dispatcher.notifySmartConnectorsChanged();
 					throw new IOException("Message not accepted by remote host, status code " + response.statusCode()
 							+ ", body " + response.body());
 				}
 			} catch (JsonProcessingException | URISyntaxException | InterruptedException e) {
-				this.remoteKerDetails = null;
 				int time = this.errorOccurred();
 				LOG.warn("Ignoring KER {} for {} minutes.", this.remoteKerUri, time);
-				dispatcher.notifySmartConnectorsChanged();
 				throw new IOException("Could not send message to remote SmartConnector.", e);
 			} catch (IOException e) {
-				this.remoteKerDetails = null;
 				int time = this.errorOccurred();
-				dispatcher.notifySmartConnectorsChanged();
 				LOG.warn("Ignoring KER {} for {} minutes.", this.remoteKerUri, time);
 				throw e;
 			}
 		} else {
 			LOG.warn("Still ignoring KER {}.", this.remoteKerUri);
-			throw new IOException("KER " + this.remoteKerUri + " is currently unavalable. Trying again later.");
+			throw new IOException("KER " + this.remoteKerUri + " is currently unavailable. Trying again later.");
 		}
 	}
 

From 1e3cd98a9a13c4dc05ab702a8892b3beeba9d4fa Mon Sep 17 00:00:00 2001
From: Barry Nouwt <barry.nouwt@tno.nl>
Date: Fri, 1 Dec 2023 18:54:00 +0100
Subject: [PATCH 19/32] When a KER is removed, its KBs should be removed also.

---
 .../runtime/messaging/RemoteKerConnection.java              | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
index af72148b..734e1835 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/RemoteKerConnection.java
@@ -241,6 +241,12 @@ public void stop() {
 			}
 		} else
 			LOG.info("Still ignoring KER {}.", this.remoteKerUri);
+
+		// if someone calls this stop method, all smart connectors should be removed
+		// from the other knowledge base store. We do this by removing the ker details
+		// and calling this method.
+		this.remoteKerDetails = null;
+		dispatcher.notifySmartConnectorsChanged();
 	}
 
 	public void sendToRemoteSmartConnector(KnowledgeMessage message) throws IOException {

From 0b455bb66205519c469a76bd60e79d947ee628c9 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Tue, 12 Dec 2023 08:22:00 +0000
Subject: [PATCH 20/32] Resolve "Improve logging when KB is stopped and its
 open handle requests are cancelled."

---
 .../rest/api/TestSuspendedKnowledgeBase.java  | 178 ++++++++++++++++++
 .../rest/api/impl/RestKnowledgeBase.java      |   6 +-
 2 files changed, 182 insertions(+), 2 deletions(-)
 create mode 100644 smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestSuspendedKnowledgeBase.java

diff --git a/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestSuspendedKnowledgeBase.java b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestSuspendedKnowledgeBase.java
new file mode 100644
index 00000000..7b14f0ff
--- /dev/null
+++ b/smart-connector-rest-dist/src/test/java/eu/knowledge/engine/rest/api/TestSuspendedKnowledgeBase.java
@@ -0,0 +1,178 @@
+package eu.knowledge.engine.rest.api;
+
+import eu.knowledge.engine.rest.RestServerHelper;
+import eu.knowledge.engine.test_utils.AsyncTester;
+import eu.knowledge.engine.test_utils.HttpTester;
+import org.junit.jupiter.api.*;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
+
+@Disabled
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+public class TestSuspendedKnowledgeBase {
+    int NUM_UNHANDLED_REQUESTS = 5;
+    CountDownLatch latch = new CountDownLatch(NUM_UNHANDLED_REQUESTS);
+    private final RestServerHelper rsh = new RestServerHelper();
+    private static final int PORT = 8280;
+
+    @BeforeAll
+    public void setUpServer() {
+        rsh.start(PORT);
+    }
+
+    @Test
+    public void testSuspendingKnowledgeBase() throws MalformedURLException {
+        URL url = new URL("http://localhost:" + PORT + "/rest");
+        HttpTester registerKb = new HttpTester(new URL(url + "/sc"),
+                "POST",
+                "{\"knowledgeBaseId\": \"http://example.com/kb1\", " +
+                        "\"knowledgeBaseName\": \"KB1\", " +
+                        "\"knowledgeBaseDescription\": \"KB1\"}", Map.of(
+                "Content-Type", "application/json",
+                "Accept", "*/*"
+        ));
+        registerKb.expectStatus(200);
+        HttpTester registerKb2 = new HttpTester(new URL(url + "/sc"),
+                "POST",
+                "{\"knowledgeBaseId\": \"http://example.com/kb2\", " +
+                        "\"knowledgeBaseName\": \"KB2\", " +
+                        "\"knowledgeBaseDescription\": \"KB2\"}", Map.of(
+                "Content-Type", "application/json",
+                "Accept", "*/*"
+        ));
+        registerKb2.expectStatus(200);
+
+
+        var sc1 = new AsyncTester(() -> {
+            try {
+                HttpTester registerAsk = new HttpTester(new URL(url + "/sc/ki"),
+                        "POST",
+                        "{\"knowledgeInteractionType\": \"AskKnowledgeInteraction\", " +
+                                "\"knowledgeInteractionName\": \"ask\"," +
+                                "\"graphPattern\": \"?a ?b ?c.\"}",
+                        Map.of(
+                                "Knowledge-Base-Id", "http://example.com/kb1",
+                                "Content-Type", "application/json",
+                                "Accept", "*/*"
+                        )
+                );
+                registerAsk.expectStatus(200);
+                System.out.println("Registered Ask");
+                HttpTester executeAsk = new HttpTester(new URL(url + "/sc/ask"),
+                        "POST", "[{}]",
+                        Map.of(
+                                "Knowledge-Base-Id", "http://example.com/kb1",
+                                "Knowledge-Interaction-Id", "http://example.com/kb1/interaction/ask",
+                                "Content-Type", "application/json",
+                                "Accept", "*/*"
+                        )
+                );
+                System.out.println("Executing Ask");
+                var body = executeAsk.getBody();
+                System.out.println(body);
+
+                for (int i = 0; i < NUM_UNHANDLED_REQUESTS; i++) {
+                    System.out.println("Making another ask");
+                    new AsyncTester(() -> {
+                        HttpTester executeAsk1;
+                        try {
+                            executeAsk1 = new HttpTester(new URL(url + "/sc/ask"),
+                                    "POST", "[{}]",
+                                    Map.of(
+                                            "Knowledge-Base-Id", "http://example.com/kb1",
+                                            "Knowledge-Interaction-Id", "http://example.com/kb1/interaction/ask",
+                                            "Content-Type", "application/json",
+                                            "Accept", "*/*"
+                                    )
+                            );
+                        } catch (MalformedURLException e) {
+                            throw new RuntimeException(e);
+                        }
+                        System.out.println("Executing Ask");
+                        latch.countDown();
+                        var body1 = executeAsk1.getBody();
+                        System.out.println(body1);
+                    }).start();
+                }
+            } catch (MalformedURLException e) {
+                System.err.println(e.getMessage());
+            }
+        });
+
+        var sc2 = new AsyncTester(() -> {
+            try {
+                HttpTester registerAnswer = new HttpTester(new URL(url + "/sc/ki"),
+                        "POST",
+                        "{\"knowledgeInteractionType\": \"AnswerKnowledgeInteraction\", " +
+                                "\"knowledgeInteractionName\": \"answer\"," +
+                                "\"graphPattern\": \"?a ?b ?c.\"}",
+                        Map.of(
+                                "Knowledge-Base-Id", "http://example.com/kb2",
+                                "Content-Type", "application/json",
+                                "Accept", "*/*"
+                        )
+                );
+                registerAnswer.expectStatus(200);
+                System.out.println("Registered Answer");
+
+                HttpTester waitForRequest = new HttpTester(new URL(url + "/sc/handle"),
+                        "GET", null,
+                        Map.of(
+                                "Knowledge-Base-Id", "http://example.com/kb2",
+                                "Content-Type", "application/json",
+                                "Accept", "*/*"
+                        )
+                );
+                var body = waitForRequest.getBody();
+                System.out.println(body);
+
+                System.out.println("Waiting for requests");
+                var postAnswer = new HttpTester(new URL(url + "/sc/handle"), "POST", """
+                          {
+                            "handleRequestId": 1,
+                            "bindingSet": [{
+                                "a": "<http://www.tno.nl/s1>",
+                                "b": "<http://www.tno.nl/s2>",
+                                "c": "<http://www.tno.nl/s3>"
+                            }]
+                          }
+                        """,
+                        Map.of("Content-Type", "application/json",
+                                "Accept", "*/*",
+                                "Knowledge-Base-Id", "http://example.com/kb2",
+                                "Knowledge-Interaction-Id", "http://example.com/kb2/interaction/answer"));
+                postAnswer.getBody();
+                System.out.println("Posted answer");
+
+                latch.await();
+
+                HttpTester deleteSC = new HttpTester(new URL(url + "/sc/"),
+                        "DELETE", "",
+                        Map.of(
+                                "Knowledge-Base-Id", "http://example.com/kb2",
+                                "Content-Type", "application/json",
+                                "Accept", "*/*"
+                        ));
+                deleteSC.expectStatus(200);
+            } catch (MalformedURLException e) {
+                System.err.println(e.getMessage());
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+        sc1.start();
+        sc2.start();
+        sc1.joinAndRethrow();
+        sc2.joinAndRethrow();
+
+    }
+
+    @AfterAll
+    public void cleanUp() {
+        rsh.cleanUp();
+    }
+}
diff --git a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
index a4a1835e..1780cfb3 100644
--- a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
+++ b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/RestKnowledgeBase.java
@@ -17,7 +17,6 @@
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
@@ -743,7 +742,10 @@ public void stop() {
 	}
 
 	private void cancelAndClearAllHandleRequests() {
-		String cancelMessage = "This KB will no longer respond, because it is stopped.";
+		List<Integer> cancelledRequests = this.toBeProcessedHandleRequests.stream().map(HandleRequest::getHandleRequestId).toList();
+		LOG.warn("KB with id " + this.knowledgeBaseId+ " has stopped. The following handle requests will be cancelled: "+cancelledRequests);
+
+		String cancelMessage = "KB with id "+ this.knowledgeBaseId +" will no longer respond, because it stopped.";
 		this.toBeProcessedHandleRequests.forEach(hr -> {
 			hr.getFuture().completeExceptionally(new CancellationException(cancelMessage));
 		});

From f457a80add84c6e0de564ac13775b103e282d57a Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 15 Dec 2023 10:36:23 +0000
Subject: [PATCH 21/32] Resolve "The ConcurrentModificationException in
 MessageDispatcher should not occur."

---
 .../runtime/messaging/MessageDispatcher.java     | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
index 7be4dede..4bc0ae5f 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/runtime/messaging/MessageDispatcher.java
@@ -2,15 +2,11 @@
 
 import java.io.IOException;
 import java.net.URI;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Set;
-import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.concurrent.LinkedBlockingQueue;
 import java.util.stream.Collectors;
 
 import org.eclipse.jetty.server.Server;
@@ -77,7 +73,8 @@ private static enum State {
 	 * replying to this message. Instead, we wait until the (remote) known Smart
 	 * Connectors change, and then try again.
 	 */
-	private final List<KnowledgeMessage> undeliverableMail = Collections.synchronizedList(new LinkedList<>());
+	private final List<KnowledgeMessage> undeliverableMail = new CopyOnWriteArrayList<>();
+	private final static int MAX_ENTRIES_UNDELIVERABLE_MAIL = 5000;
 
 	/**
 	 * Construct the {@link MessageDispatcher} in a distributed mode, with an
@@ -237,6 +234,14 @@ void deliverToLocalSmartConnector(KnowledgeMessage message) throws IOException {
 			// might cause other Smart Connectors to wait for responses indefinately
 			LOG.warn("Received message from unknown Knowledge Base: " + message.getFromKnowledgeBase()
 					+ ", I only know " + knowledgeBaseIds);
+
+			if (this.undeliverableMail.size() >= MAX_ENTRIES_UNDELIVERABLE_MAIL) {
+				int numMessagesToRemove = this.undeliverableMail.size() - MAX_ENTRIES_UNDELIVERABLE_MAIL;
+				for (int i = 0; i <= numMessagesToRemove; i++) {
+					KnowledgeMessage removedMessage = this.undeliverableMail.remove(0);
+					LOG.warn("Too many undelivered messages. Removing the oldest message with ID " + removedMessage.getMessageId() + " to make space for a new message.");
+				}
+			}
 			this.undeliverableMail.add(message);
 
 			// Force a refresh of the KERs from the Knowledge Directory
@@ -308,7 +313,6 @@ public void removeListener(KnowledgeDirectoryProxyListener listener) {
 	 * comes.
 	 */
 	private void tryDeliverUndeliveredMail() throws IOException {
-
 		Iterator<KnowledgeMessage> it = undeliverableMail.iterator();
 		Set<KnowledgeMessage> toBeRemoved = new HashSet<>();
 		while (it.hasNext()) {

From d17312bf900c4be67fc2aec2687178a3ada890e4 Mon Sep 17 00:00:00 2001
From: lathouwerssam <sophie.lathouwers@tno.nl>
Date: Fri, 15 Dec 2023 13:28:57 +0100
Subject: [PATCH 22/32] Prepare for version 1.2.3

---
 README.md                                     | 24 +++++++++----------
 .../src/main/resources/openapi-admin-ui.yaml  |  2 +-
 docs/04_distributed_mode.md                   |  6 ++---
 examples/authentication/docker-compose.yml    |  6 ++---
 examples/multiple-runtimes/docker-compose.yml |  8 +++----
 examples/reasoner/docker-compose.yml          |  2 +-
 examples/rest-api/docker-compose.yml          |  2 +-
 examples/unreachable-runtimes/Dockerfile      |  2 +-
 .../unreachable-runtimes/docker-compose.yml   |  2 +-
 pom.xml                                       |  2 +-
 .../src/main/resources/openapi-sc.yaml        |  2 +-
 11 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/README.md b/README.md
index f5aab820..5247f22c 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ The easiest way to start a Knowledge Engine runtime is with Docker:
 ```bash
 docker run \
 	-p 8280:8280 \
-	ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+	ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
 ```
 
 The Knowledge Engine runtime is now available to use via the REST API at base URL `http://localhost:8280/rest` on your host machine.
@@ -93,7 +93,7 @@ docker run \
   -p 8081:8081 \
   -e KD_URL=https://knowledge-directory.example.org \
   -e KE_RUNTIME_EXPOSED_URL=https://your-domain.example.org:8081 \
-  ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+  ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
 ```
 
 ### Running with Java
@@ -111,7 +111,7 @@ export KE_RUNTIME_EXPOSED_URL=https://your-domain.example.org:8081
 # Start it. The argument (8280) denotes the port number at which it
 # will listen for connections to the Knowledge Engine REST API.
 java -jar -Dorg.slf4j.simpleLogger.logFile=smart-connector.log \
-  smart-connector-rest-dist-1.2.2-with-dependencies.jar 8280
+  smart-connector-rest-dist-1.2.3-with-dependencies.jar 8280
 ```
 
 The JAR can be retrieved by compiling the project:
@@ -205,17 +205,17 @@ These are instructions on what to do when we release a new version of the knowle
 5. Build and push the new Docker images to GitLab:
 
 ```bash
-docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/smart-connector-rest-dist:1.2.2 --push
-docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/knowledge-directory:1.2.2 --push
-docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/admin-ui:1.2.2 --push
+docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/smart-connector-rest-dist:1.2.3 --push
+docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/knowledge-directory:1.2.3 --push
+docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag docker-registry.inesctec.pt/interconnect/knowledge-engine/admin-ui:1.2.3 --push
 ```
 
 6. Build and push the new Docker images to GitHub:
 
 ```bash
-docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/smart-connector:1.2.2 --push
-docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2 --push
-docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/admin-ui:1.2.2 --push
+docker buildx build ./smart-connector-rest-dist --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/smart-connector:1.2.3 --push
+docker buildx build ./knowledge-directory --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.3 --push
+docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/tno/knowledge-engine/admin-ui:1.2.3 --push
 ```
 
 7. Prepare the next SNAPSHOT version and make a commit for that too.
@@ -232,7 +232,7 @@ docker buildx build ./admin-ui --platform linux/arm64,linux/amd64 --tag ghcr.io/
 10. Inform mailing list(s) (and [the blog](https://www.knowledge-engine.eu/blog/)) about the new release.
 
 ## (advanced) Administering a Knowledge Engine runtime
-To start a new instance of the REST API knowledge engine version 1.2.2, make sure you have `git checkout 1.2.2` the tag `1.2.2`. Now make sure you run the `mvn clean install` command successfully from the root of the repository.
+To start a new instance of the REST API knowledge engine version 1.2.3, make sure you have `git checkout 1.2.3` the tag `1.2.3`. Now make sure you run the `mvn clean install` command successfully from the root of the repository.
 
 ### Starting the Knowledge Engine in local mode
 When no additional configuration parameters are provided, the Knowledge Engine will by default run in local mode. This means you can create multiple smart connectors that can communicate with each other through the REST API, but the Knowledge Engine will not connect to a knowledge directory and will not be able to connect with smart connectors running in other runtimes.
@@ -246,13 +246,13 @@ cd smart-connector-rest-dist/target
 Finally, start the server (note that you can configure a log file by including the `-Dorg.slf4j.simpleLogger.logFile=ke.log` system property to the JVM):
 
 ```bash
-java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
+java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.3.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
 ```
 
 If you want to run in it in the background, you can use the `nohup` linux command (which does not use the simpleLogger configuration system property, but redirects the standard err/out):
 
 ```bash
-nohup java -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280 > ke.log
+nohup java -cp "smart-connector-rest-dist-1.2.3.jar:dependency/*" eu.knowledge.engine.rest.Main 8280 > ke.log
 ```
 
 ### Starting the Knowledge Engine in distributed mode
diff --git a/admin-ui/src/main/resources/openapi-admin-ui.yaml b/admin-ui/src/main/resources/openapi-admin-ui.yaml
index 0e3e0e12..f5d6a6b2 100644
--- a/admin-ui/src/main/resources/openapi-admin-ui.yaml
+++ b/admin-ui/src/main/resources/openapi-admin-ui.yaml
@@ -5,7 +5,7 @@ info:
   description:
     This API provides information on Knowledge Engine Runtimes (todo), Smart Connectors, Knowledge Bases, and Knowledge
     Interactions in a Knowledge Engine Network.
-  version: 1.2.2
+  version: 1.2.3
   
 paths:
   /rest/admin/sc/all/{include-meta}:
diff --git a/docs/04_distributed_mode.md b/docs/04_distributed_mode.md
index 604e70c7..410b61f0 100644
--- a/docs/04_distributed_mode.md
+++ b/docs/04_distributed_mode.md
@@ -16,7 +16,7 @@ First of all, you need to start a knowledge directory. The desired port number f
 ```bash
 cd knowledge-directory/target/
 
-java -Dorg.slf4j.simpleLogger.logFile=kd.log -cp "knowledge-directory-1.2.2.jar:dependency/*" eu.knowledge.engine.knowledgedirectory.Main 8080
+java -Dorg.slf4j.simpleLogger.logFile=kd.log -cp "knowledge-directory-1.2.3.jar:dependency/*" eu.knowledge.engine.knowledgedirectory.Main 8080
 ```
 
 The `nohup` command can be used to run the process in the background. On overview of the registered Knowledge Engine runtimes can be found on `http://localhost:8080/ker/` (or another host or port if you desire).
@@ -26,7 +26,7 @@ Once the knowledge directory is up and running, the REST server can be started.
 | Key    | Descrption                                     |
 |--------|------------------------------------------------|
 | KD_URL | URL where the knowledge directory can be found. This url should not end with a slash (`/`).|
-| KE_RUNTIME_EXPOSED_URL | URL where other smart connectors (peers) can contact this Knowledge Engine runtime. This allows your Knowledge Engine to be behind a reverse proxy and use TLS. Note that the URL should include the scheme like `http://...` or `https://...` and should not end with a slash (`/`).
+| KE_RUNTIME_EXPOSED_URL | URL where other smart connectors (peers) can contact this Knowledge Engine runtime. This allows your Knowledge Engine to be behind a reverse proxy and use TLS. Note that the URL should include the scheme like `http://...` or `https://...` and should not end with a slash (`/`).|
 | KE_RUNTIME_PORT | Port where where this Knowledge Engine instance will listen for new peer connections |
 | KE_RUNTIME_HOSTNAME (deprecated) | Hostname where other smart connectors (peers) can contact this Knowledge Engine instance. This variable is superseded by (and conflicts with) KE_RUNTIME_EXPOSED_URL|
 
@@ -39,7 +39,7 @@ export KD_URL=http://localhost:8080
 export KE_RUNTIME_EXPOSED_URL=http://localhost:8081
 export KE_RUNTIME_PORT=8081
 
-java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.2.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
+java -Dorg.slf4j.simpleLogger.logFile=ke.log -cp "smart-connector-rest-dist-1.2.3.jar:dependency/*" eu.knowledge.engine.rest.Main 8280
 ```
 
 ### Using Basic Authentication to secure data exchange
diff --git a/examples/authentication/docker-compose.yml b/examples/authentication/docker-compose.yml
index 75fd046d..0212f006 100644
--- a/examples/authentication/docker-compose.yml
+++ b/examples/authentication/docker-compose.yml
@@ -9,15 +9,15 @@ services:
     depends_on:
       - knowledge-directory
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.3
   runtime-1:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     environment:
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KD_URL: http://thisisausername:thisisapassword@nginx/kd
       KE_RUNTIME_EXPOSED_URL: http://thisisausername:thisisapassword@nginx/ker1
   runtime-2:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     environment:
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KD_URL: http://thisisausername:thisisapassword@nginx/kd
diff --git a/examples/multiple-runtimes/docker-compose.yml b/examples/multiple-runtimes/docker-compose.yml
index f02a3626..65f64eac 100644
--- a/examples/multiple-runtimes/docker-compose.yml
+++ b/examples/multiple-runtimes/docker-compose.yml
@@ -2,25 +2,25 @@ services:
   # This is the knowledge directory, facilitating discovery between different
   # runtimes. It exposes its service over port 8282.
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.3
 
   # These services are seperate Knowledge Engine runtime, which can host
   # multiple smart connectors. Note that the REST API port is a DIFFERENT port
   # number than the ones configured below. It is still the default 8280.
   runtime-1:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     environment: 
       KE_RUNTIME_PORT: 8081 # The port that the KE uses to listen for inter-KE-runtime communication.
       KE_RUNTIME_EXPOSED_URL: http://runtime-1:8081 # The URL where the runtime is available for inter-runtime communication from the outside.
       KD_URL: http://knowledge-directory:8282
   runtime-2:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-2:8081
       KD_URL: http://knowledge-directory:8282
   runtime-3:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     environment: 
       KE_RUNTIME_PORT: 8081
       KE_RUNTIME_EXPOSED_URL: http://runtime-3:8081
diff --git a/examples/reasoner/docker-compose.yml b/examples/reasoner/docker-compose.yml
index c9bd43e3..107bc2e5 100644
--- a/examples/reasoner/docker-compose.yml
+++ b/examples/reasoner/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   knowledge-engine:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
   kb1:
     build: ../common/asking_kb
     environment:
diff --git a/examples/rest-api/docker-compose.yml b/examples/rest-api/docker-compose.yml
index 483a0c2d..10731bff 100644
--- a/examples/rest-api/docker-compose.yml
+++ b/examples/rest-api/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   knowledge-engine:
-    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+    image: ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
     healthcheck:
       test: curl -f http://localhost:8280/rest/sc
       interval: 1s
diff --git a/examples/unreachable-runtimes/Dockerfile b/examples/unreachable-runtimes/Dockerfile
index 108fd9a3..5114f37f 100644
--- a/examples/unreachable-runtimes/Dockerfile
+++ b/examples/unreachable-runtimes/Dockerfile
@@ -1,4 +1,4 @@
-FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.2
+FROM ghcr.io/tno/knowledge-engine/smart-connector:1.2.3
 
 RUN apt update -y
 RUN apt-get install iptables sudo -y
diff --git a/examples/unreachable-runtimes/docker-compose.yml b/examples/unreachable-runtimes/docker-compose.yml
index 2498873f..95573d9a 100644
--- a/examples/unreachable-runtimes/docker-compose.yml
+++ b/examples/unreachable-runtimes/docker-compose.yml
@@ -2,7 +2,7 @@ services:
   # This is the knowledge directory, facilitating discovery between different
   # runtimes. It exposes its service over port 8282.
   knowledge-directory:
-    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.2
+    image: ghcr.io/tno/knowledge-engine/knowledge-directory:1.2.3
 
   # These services are seperate Knowledge Engine runtime, which can host
   # multiple smart connectors. Note that the REST API port is a DIFFERENT port
diff --git a/pom.xml b/pom.xml
index 70c66722..77e5c0ea 100644
--- a/pom.xml
+++ b/pom.xml
@@ -74,7 +74,7 @@
 		<java.version>17</java.version>
 		<maven.compiler.source>17</maven.compiler.source>
 		<maven.compiler.target>17</maven.compiler.target>
-		<revision>1.2.3-SNAPSHOT</revision>
+		<revision>1.2.3</revision>
 	</properties>
 
 	<dependencyManagement>
diff --git a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
index 97a04814..274a2ef1 100644
--- a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
+++ b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
@@ -7,7 +7,7 @@ info:
     Interactions are (un)registered and data is exchanged. Each Smart Connector
     is coupled with a Knowledge Base Id, so every rest call uses this Knowledge
     Base Id to identify yourself.
-  version: 1.2.3-SNAPSHOT
+  version: 1.2.3
   
 paths:
   /sc:

From ab451fc4883a841bf602884067cecca88c67edcb Mon Sep 17 00:00:00 2001
From: lathouwerssam <sophie.lathouwers@tno.nl>
Date: Fri, 15 Dec 2023 14:12:46 +0100
Subject: [PATCH 23/32] Prepare for version 1.2.4-SNAPSHOT

---
 pom.xml                                                        | 2 +-
 smart-connector-rest-server/src/main/resources/openapi-sc.yaml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pom.xml b/pom.xml
index 77e5c0ea..16e7c9b0 100644
--- a/pom.xml
+++ b/pom.xml
@@ -74,7 +74,7 @@
 		<java.version>17</java.version>
 		<maven.compiler.source>17</maven.compiler.source>
 		<maven.compiler.target>17</maven.compiler.target>
-		<revision>1.2.3</revision>
+		<revision>1.2.4-SNAPSHOT</revision>
 	</properties>
 
 	<dependencyManagement>
diff --git a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
index 274a2ef1..0a253492 100644
--- a/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
+++ b/smart-connector-rest-server/src/main/resources/openapi-sc.yaml
@@ -7,7 +7,7 @@ info:
     Interactions are (un)registered and data is exchanged. Each Smart Connector
     is coupled with a Knowledge Base Id, so every rest call uses this Knowledge
     Base Id to identify yourself.
-  version: 1.2.3
+  version: 1.2.4-SNAPSHOT
   
 paths:
   /sc:

From c76be470088399e5af2d6c1c865e1fe17f69a797 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Wed, 20 Dec 2023 13:34:50 +0000
Subject: [PATCH 24/32] Resolve "Improve logging by removing possibly sensitive
 data to end up in the log file of a Knowledge Engine Runtime."

---
 .../smartconnector/impl/ReasonerProcessor.java   |  4 ++--
 .../impl/SerialMatchingProcessor.java            | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
index 37c73879..7518d363 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/ReasonerProcessor.java
@@ -432,7 +432,7 @@ public CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet> handle(
 				});
 
 			} catch (IOException e) {
-				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), askMessage);
+				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), askMessage.getMessageId());
 				LOG.debug("", e);
 				bsFuture = new CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet>();
 				bsFuture.complete(new eu.knowledge.engine.reasoner.api.BindingSet());
@@ -494,7 +494,7 @@ public CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet> handle(
 				});
 
 			} catch (IOException e) {
-				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), postMessage);
+				LOG.warn("Errors like '{}' should not occur while sending: {}", e.getMessage(), postMessage.getMessageId());
 				LOG.debug("", e);
 				bsFuture = new CompletableFuture<eu.knowledge.engine.reasoner.api.BindingSet>();
 				bsFuture.complete(new eu.knowledge.engine.reasoner.api.BindingSet());
diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
index 9e5d20e7..72472c6c 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/SerialMatchingProcessor.java
@@ -118,18 +118,18 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 						try {
 							this.answerMessageFuture = this.messageRouter.sendAskMessage(askMessage);
 							this.previousSend = Instant.now();
-							
+
 							answerMessageFuture.exceptionally(e -> {
 								this.LOG.warn("Error '{}' occurred while waiting for response to: {}",
 										e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
-										askMessage);
+										askMessage.getMessageId());
 								this.LOG.debug("", e);
 
 								// continue with the work, otherwise this process will come to a halt.
 								this.checkOtherKnowledgeInteraction(bindingSet);
 								return null;
 							});
-							
+
 							this.answerMessageFuture.thenAccept(aMessage -> {
 								try {
 									this.answerMessageFuture = null;
@@ -149,8 +149,8 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 								}
 							});
 						} catch (IOException e) {
-							this.LOG.warn("Error '{}' occurred while sending: {}",
-									e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), askMessage);
+							this.LOG.warn("Error '{}' occurred while sending {}",
+									e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(), askMessage.getClass().getSimpleName());
 							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.
@@ -181,7 +181,7 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 							reactMessageFuture.exceptionally(e -> {
 								this.LOG.warn("Error '{}' occurred while waiting for response to: {}",
 										e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
-										postMessage);
+										postMessage.getMessageId());
 								this.LOG.debug("", e);
 
 								// continue with the work, otherwise this process will come to a halt.
@@ -214,9 +214,9 @@ private void checkOtherKnowledgeInteraction(BindingSet bindingSet) {
 							});
 						} catch (IOException e) {
 
-							this.LOG.warn("Error '{}' occurred while sending: {}",
+							this.LOG.warn("Error '{}' occurred while sending {}",
 									e.getMessage() != null ? e.getMessage() : e.getClass().getSimpleName(),
-									postMessage);
+									postMessage.getClass().getSimpleName());
 							this.LOG.debug("", e);
 
 							// continue with the work, otherwise this process will come to a halt.

From e2d309c2e6da3f23046978f75913d9ec3e0f6c5d Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Wed, 20 Dec 2023 14:27:22 +0000
Subject: [PATCH 25/32] Resolve "Check whether the FULL_MATCH_ONLY strategy for
 the reasoner for meta knowledge interactions does not allow a KB to subscribe
 to part of the metadata and receive updates."

---
 ...tMetadataKnowledgeInteractionMatching.java | 125 ++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestMetadataKnowledgeInteractionMatching.java

diff --git a/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestMetadataKnowledgeInteractionMatching.java b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestMetadataKnowledgeInteractionMatching.java
new file mode 100644
index 00000000..05f3bab8
--- /dev/null
+++ b/smart-connector/src/test/java/eu/knowledge/engine/smartconnector/api/TestMetadataKnowledgeInteractionMatching.java
@@ -0,0 +1,125 @@
+package eu.knowledge.engine.smartconnector.api;
+
+import eu.knowledge.engine.smartconnector.util.KnowledgeNetwork;
+import eu.knowledge.engine.smartconnector.util.MockedKnowledgeBase;
+import org.apache.jena.shared.PrefixMapping;
+import org.apache.jena.sparql.graph.PrefixMappingMem;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.concurrent.ExecutionException;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * This test checks whether we can use knowledge interactions to react to (part of) the metadata of a knowledge base
+ * We thought this would be impossible right now as someone tried to disable this because of the slow graph matching algorithm.
+ * However, we can still match on a small graph pattern, this may be caused by the order in which it is checked whether
+ * one pattern is a subset of the other.
+ */
+public class TestMetadataKnowledgeInteractionMatching {
+    private static final Logger LOG = LoggerFactory.getLogger(TestDynamicSemanticComposition.class);
+
+    private static KnowledgeNetwork kn;
+    private static MockedKnowledgeBase kb1, kb2;
+    private static PrefixMappingMem prefixes;
+
+
+    @BeforeEach
+    public void setup() {
+        kn = new KnowledgeNetwork();
+        kb1 = new MockedKnowledgeBase("Kb1");
+        kb1.setReasonerEnabled(true);
+
+        prefixes = new PrefixMappingMem();
+        prefixes.setNsPrefixes(PrefixMapping.Standard);
+        prefixes.setNsPrefix("ke", Vocab.ONTO_URI);
+    }
+
+    @Test
+    public void testNewKB() {
+        ReactKnowledgeInteraction rKI =  new ReactKnowledgeInteraction(new CommunicativeAct(new HashSet<>(Arrays.asList(Vocab.INFORM_PURPOSE)),
+                new HashSet<>(Arrays.asList(Vocab.NEW_KNOWLEDGE_PURPOSE))), new GraphPattern(prefixes,
+                "?k ke:hasName ?n . ?k ke:hasDescription ?d ."
+        ), null, true);
+        kb1.register(rKI, ((anRKI, aReactExchangeInfo) -> {
+            var argument = aReactExchangeInfo.getArgumentBindings();
+            Iterator<Binding> iter = argument.iterator();
+            assertTrue(iter.hasNext(), "There should be matches on metadata when a new KB is registered.");
+            return new BindingSet();
+        }));
+        kn.addKB(kb1);
+        kn.sync();
+
+        kb2 = new MockedKnowledgeBase("Kb2");
+        kb2.setReasonerEnabled(true);
+        kn.addKB(kb2);
+        kn.sync();
+    }
+
+    @Test
+    public void testChangedKB() {
+        ReactKnowledgeInteraction rKI =  new ReactKnowledgeInteraction(new CommunicativeAct(new HashSet<>(Arrays.asList(Vocab.INFORM_PURPOSE)),
+                new HashSet<>(Arrays.asList(Vocab.CHANGED_KNOWLEDGE_PURPOSE))), new GraphPattern(prefixes,
+                "?k ke:hasName ?n . ?k ke:hasDescription ?d ."
+        ), null, true);
+        kb1.register(rKI, ((anRKI, aReactExchangeInfo) -> {
+            var argument = aReactExchangeInfo.getArgumentBindings();
+            Iterator<Binding> iter = argument.iterator();
+            assertTrue(iter.hasNext(), "There should be matches on metadata when the network changes.");
+            return new BindingSet();
+        }));
+        kn.addKB(kb1);
+        kn.sync();
+
+        kb2 = new MockedKnowledgeBase("Kb2");
+        kb2.setReasonerEnabled(true);
+        kn.addKB(kb2);
+        kn.sync();
+
+        GraphPattern gp1 = new GraphPattern(prefixes, "?a <https://www.tno.nl/example/b> ?c.");
+        AnswerKnowledgeInteraction aKI = new AnswerKnowledgeInteraction(new CommunicativeAct(), gp1);
+        kb1.register(aKI, (anAKI, anAnswerExchangeInfo) -> new BindingSet());
+    }
+
+    @Test
+    public void testRemovedKB() {
+        ReactKnowledgeInteraction rKI =  new ReactKnowledgeInteraction(new CommunicativeAct(new HashSet<>(Arrays.asList(Vocab.INFORM_PURPOSE)),
+                new HashSet<>(Arrays.asList(Vocab.REMOVED_KNOWLEDGE_PURPOSE))), new GraphPattern(prefixes,
+                "?k ke:hasName ?n . ?k ke:hasDescription ?d ."
+        ), null, true);
+        kb1.register(rKI, ((anRKI, aReactExchangeInfo) -> {
+            var argument = aReactExchangeInfo.getArgumentBindings();
+            Iterator<Binding> iter = argument.iterator();
+            assertTrue(iter.hasNext(), "There should be matches on metadata when a KB is removed from the network.");
+            return new BindingSet();
+        }));
+        kn.addKB(kb1);
+        kb2 = new MockedKnowledgeBase("Kb2");
+        kb2.setReasonerEnabled(true);
+        kn.addKB(kb2);
+        kn.sync();
+
+        kb2.stop();
+    }
+
+    @AfterEach
+    public void cleanup() {
+        try {
+            kb1.stop();
+        } catch (IllegalStateException e) {
+            LOG.error("Stopping a knowledge base should succeed: {}", e.getMessage());
+        }
+        try {
+            kb2.stop();
+        } catch (IllegalStateException e) {
+            LOG.error("Stopping a knowledge base should succeed. {}", e.getMessage());
+        }
+    }
+}

From 210369b08f132228ae9d56d79c171378fc429246 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Mon, 8 Jan 2024 10:23:36 +0000
Subject: [PATCH 26/32] Resolve "Improve logging of "The SmartConnector cannot
 be used anymore once it is stopped" this error."

---
 .../api/impl/KnowledgeInteractionLifeCycleApiServiceImpl.java   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/KnowledgeInteractionLifeCycleApiServiceImpl.java b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/KnowledgeInteractionLifeCycleApiServiceImpl.java
index d817e2f1..a4e11766 100644
--- a/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/KnowledgeInteractionLifeCycleApiServiceImpl.java
+++ b/smart-connector-rest-server/src/main/java/eu/knowledge/engine/rest/api/impl/KnowledgeInteractionLifeCycleApiServiceImpl.java
@@ -68,7 +68,7 @@ public Response scKiPost(String knowledgeBaseId, KnowledgeInteractionBase knowle
 		String kiId;
 		try {
 			kiId = restKb.register(knowledgeInteraction);
-		} catch (IllegalArgumentException e) {
+		} catch (IllegalStateException | IllegalArgumentException e) {
 			var resposne = new ResponseMessage();
 			resposne.setMessageType("error");
 			resposne.setMessage(e.getMessage());

From d806a069c3bd4851c1be4dee4f38b8c5ecbb5411 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 12 Jan 2024 09:16:40 +0000
Subject: [PATCH 27/32] Resolve "Move log statement regarding meta data
 exchange to debug level."

---
 .../impl/InteractionProcessorImpl.java               | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/InteractionProcessorImpl.java b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/InteractionProcessorImpl.java
index 7c8f03d2..61859e79 100644
--- a/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/InteractionProcessorImpl.java
+++ b/smart-connector/src/main/java/eu/knowledge/engine/smartconnector/impl/InteractionProcessorImpl.java
@@ -211,7 +211,11 @@ public CompletableFuture<AnswerMessage> processAskFromMessageRouter(AskMessage a
 		var handler = this.myKnowledgeBaseStore.getAnswerHandler(answerKnowledgeInteractionId);
 		// TODO This should happen in the single thread for the knowledge base
 
-		LOG.info("Contacting my KB to answer KI <{}>", answerKnowledgeInteractionId);
+		if (answerKnowledgeInteraction.isMeta()) {
+			LOG.debug("Contacting my KB to answer KI <{}>", answerKnowledgeInteractionId);
+		} else {
+			LOG.info("Contacting my KB to answer KI <{}>", answerKnowledgeInteractionId);
+		}
 
 		var aei = new AnswerExchangeInfo(anAskMsg.getBindings(), anAskMsg.getFromKnowledgeBase(),
 				anAskMsg.getFromKnowledgeInteraction());
@@ -311,7 +315,11 @@ public CompletableFuture<ReactMessage> processPostFromMessageRouter(PostMessage
 				aPostMsg.getFromKnowledgeInteraction());
 
 		// TODO This should happen in the single thread for the knowledge base
-		LOG.info("Contacting my KB to react to KI <{}>", reactKnowledgeInteractionId);
+		if (reactKnowledgeInteraction.isMeta()) {
+			LOG.debug("Contacting my KB to react to KI <{}>", reactKnowledgeInteractionId);
+		} else {
+			LOG.info("Contacting my KB to react to KI <{}>", reactKnowledgeInteractionId);
+		}
 
 		future = handler.reactAsync(reactKnowledgeInteraction, rei);
 

From fbf952f81fad6aec53b6e02eccdbae7c8b44ddea Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 12 Jan 2024 11:52:48 +0100
Subject: [PATCH 28/32] Update README.md

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 5247f22c..ffcd37a6 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-*This software is in development ([TRL 6](https://en.wikipedia.org/wiki/Technology_readiness_level)).*
+bla*This software is in development ([TRL 6](https://en.wikipedia.org/wiki/Technology_readiness_level)).*
 
 # Knowledge Engine
 

From 07bf7877cac4635821ce9bfe99bb0a2f2c7de432 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 12 Jan 2024 11:59:49 +0100
Subject: [PATCH 29/32] Update README.md

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index ffcd37a6..5247f22c 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-bla*This software is in development ([TRL 6](https://en.wikipedia.org/wiki/Technology_readiness_level)).*
+*This software is in development ([TRL 6](https://en.wikipedia.org/wiki/Technology_readiness_level)).*
 
 # Knowledge Engine
 

From ef5273a10c269a105cb2dad7c639a1ec1526b9e1 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Fri, 12 Jan 2024 17:18:29 +0100
Subject: [PATCH 30/32] Create initial workflow

---
 .github/workflows/maven.yml | 42 +++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 .github/workflows/maven.yml

diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
new file mode 100644
index 00000000..8f417d0c
--- /dev/null
+++ b/.github/workflows/maven.yml
@@ -0,0 +1,42 @@
+# This workflow will build a Java project with Maven, and cache/restore any dependencies to improve the workflow execution time
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-java-with-maven
+
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: Java CI with Maven
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  MAVEN_OPTS: -Dhttps.protocols=TLSv1.2 -Dmaven.repo.local=$CI_PROJECT_DIR/.m2/repository -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=WARN -Dorg.slf4j.simpleLogger.showDateTime=true -Djava.awt.headless=true
+  MAVEN_CLI_OPTS: --batch-mode --errors --fail-at-end --show-version
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    container: maven:3.8.7-eclipse-temurin-17-alpine
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Compile test source code with Maven
+      run: mvn $MAVEN_CLI_OPTS test-compile
+  verify:
+    needs: [build]
+    runs-on: ubuntu-latest
+    container: maven:3.8.7-eclipse-temurin-17-alpine
+    
+    steps:
+    - name: Run the Maven verify phase
+      run: mvn $MAVEN_CLI_OPTS verify
+    
+
+    # Optional: Uploads the full dependency graph to GitHub to improve the quality of Dependabot alerts this repository can receive
+    - name: Update dependency graph
+      uses: advanced-security/maven-dependency-submission-action@571e99aab1055c2e71a1e2309b9691de18d6b7d6

From c698e9ff544c136e63be51df49e0bca6dea371f7 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Mon, 15 Jan 2024 09:33:44 +0100
Subject: [PATCH 31/32] Update maven.yml

---
 .github/workflows/maven.yml | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index 8f417d0c..e9a83555 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -27,15 +27,8 @@ jobs:
     - uses: actions/checkout@v4
     - name: Compile test source code with Maven
       run: mvn $MAVEN_CLI_OPTS test-compile
-  verify:
-    needs: [build]
-    runs-on: ubuntu-latest
-    container: maven:3.8.7-eclipse-temurin-17-alpine
-    
-    steps:
     - name: Run the Maven verify phase
       run: mvn $MAVEN_CLI_OPTS verify
-    
 
     # Optional: Uploads the full dependency graph to GitHub to improve the quality of Dependabot alerts this repository can receive
     - name: Update dependency graph

From 3c1a1230369f78ca755bf8d87bd8b0432f34f4c1 Mon Sep 17 00:00:00 2001
From: Sophie Lathouwers <sophie.lathouwers@tno.nl>
Date: Mon, 15 Jan 2024 09:52:12 +0100
Subject: [PATCH 32/32] Update maven.yml

---
 .github/workflows/maven.yml | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index e9a83555..170a9c74 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -29,7 +29,3 @@ jobs:
       run: mvn $MAVEN_CLI_OPTS test-compile
     - name: Run the Maven verify phase
       run: mvn $MAVEN_CLI_OPTS verify
-
-    # Optional: Uploads the full dependency graph to GitHub to improve the quality of Dependabot alerts this repository can receive
-    - name: Update dependency graph
-      uses: advanced-security/maven-dependency-submission-action@571e99aab1055c2e71a1e2309b9691de18d6b7d6