Added Prioritybased rate limiter

solr/core/src/java/org/apache/solr/core/RateLimiterConfig.java

@@ -32,6 +32,7 @@ public class RateLimiterConfig {
   public final int allowedRequests;
   public final boolean isSlotBorrowingEnabled;
   public final int guaranteedSlotsThreshold;
+  public final boolean priorityBasedEnabled;
 
   /**
    * We store the config definition in order to determine whether anything has changed that would
@@ -49,29 +50,33 @@ public RateLimiterConfig(
       int guaranteedSlotsThreshold,
       long waitForSlotAcquisition,
       int allowedRequests,
-      boolean isSlotBorrowingEnabled) {
+      boolean isSlotBorrowingEnabled,
+      boolean priorityBasedEnabled) {
     this(
         requestType,
         makePayload(
             isEnabled,
             guaranteedSlotsThreshold,
             waitForSlotAcquisition,
             allowedRequests,
-            isSlotBorrowingEnabled));
+            isSlotBorrowingEnabled,
+            priorityBasedEnabled));
   }
 
   private static RateLimiterPayload makePayload(
       boolean isEnabled,
       int guaranteedSlotsThreshold,
       long waitForSlotAcquisition,
       int allowedRequests,
-      boolean isSlotBorrowingEnabled) {
+      boolean isSlotBorrowingEnabled,
+      boolean priorityBasedEnabled) {
     RateLimiterPayload ret = new RateLimiterPayload();
     ret.enabled = isEnabled;
     ret.allowedRequests = allowedRequests;
     ret.guaranteedSlots = guaranteedSlotsThreshold;
     ret.slotBorrowingEnabled = isSlotBorrowingEnabled;
     ret.slotAcquisitionTimeoutInMS = Math.toIntExact(waitForSlotAcquisition);
+    ret.priorityBasedEnabled = priorityBasedEnabled;
     return ret;
   }
 
@@ -98,6 +103,9 @@ public RateLimiterConfig(SolrRequest.SolrRequestType requestType, RateLimiterPay
             ? DEFAULT_SLOT_ACQUISITION_TIMEOUT_MS
             : definition.slotAcquisitionTimeoutInMS.longValue();
 
+    priorityBasedEnabled =
+        definition.priorityBasedEnabled == null ? false : definition.priorityBasedEnabled;
+
     this.definition = definition;
   }
 
@@ -125,6 +133,7 @@ public String toString() {
     sb.append(", guaranteedSlots=").append(guaranteedSlotsThreshold);
     sb.append(", borrowEnabled=").append(isSlotBorrowingEnabled);
     sb.append(", waitForSlotMillis=").append(waitForSlotAcquisition);
+    sb.append(", priorityBasedEnabled=").append(priorityBasedEnabled);
     return sb.append('}').toString();
   }
 }

solr/core/src/java/org/apache/solr/servlet/PriorityBasedRateLimiter.java

@@ -0,0 +1,127 @@
+package org.apache.solr.servlet;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import javax.servlet.http.HttpServletRequest;
+import org.apache.solr.common.SolrException;
+import org.apache.solr.core.RateLimiterConfig;
+
+/**
+ * PriorityBasedRateLimiter allocates the slot based on their request priority Currently, it has two
+ * priorities FOREGROUND and BACKGROUND Requests. Client can pass the {@link
+ * org.apache.solr.common.params.CommonParams} SOLR_REQUEST_TYPE_PARAM request header to indicate
+ * the foreground and background request. Foreground requests has high priority than background
+ * requests
+ */
+public class PriorityBasedRateLimiter extends RequestRateLimiter {
+  public static final String SOLR_REQUEST_PRIORITY_PARAM = "Solr-Request-Priority";
+  private final AtomicInteger activeRequests = new AtomicInteger();
+  private final Semaphore numRequestsAllowed;
+
+  private final int totalAllowedRequests;
+
+  private final LinkedBlockingQueue<CountDownLatch> waitingList = new LinkedBlockingQueue<>();
+
+  private final long waitTimeoutInMillis;
+
+  public PriorityBasedRateLimiter(RateLimiterConfig rateLimiterConfig) {
+    super(rateLimiterConfig);
+    this.numRequestsAllowed = new Semaphore(rateLimiterConfig.allowedRequests, true);
+    this.totalAllowedRequests = rateLimiterConfig.allowedRequests;
+    this.waitTimeoutInMillis = rateLimiterConfig.waitForSlotAcquisition;
+  }
+
+  @Override
+  public SlotReservation handleRequest(HttpServletRequest request) {
+    if (!rateLimiterConfig.isEnabled) {
+      return UNLIMITED;
+    }
+    RequestPriorities requestPriority = getRequestPriority(request);
+    if (requestPriority == null) {
+      throw new SolrException(
+          SolrException.ErrorCode.BAD_REQUEST,
+          "Request priority header is not defined or not set properly");
+    }
+    try {
+      if (!acquire(requestPriority)) {
+        return null;
+      }
+    } catch (InterruptedException ie) {
+      return null;
+    }
+    return () -> PriorityBasedRateLimiter.this.release();
+  }
+
+  private boolean acquire(RequestPriorities priority) throws InterruptedException {
+    if (priority.equals(RequestPriorities.FOREGROUND)) {
+      return nextInQueue();
+    } else if (priority.equals(RequestPriorities.BACKGROUND)) {
+      if (this.activeRequests.get() < this.totalAllowedRequests) {
+        return nextInQueue();
+      } else {
+        CountDownLatch wait = new CountDownLatch(1);
+        this.waitingList.put(wait);
+        return wait.await(this.waitTimeoutInMillis, TimeUnit.MILLISECONDS) && nextInQueue();
+      }
+    }
+    return true;
+  }
+
+  private boolean nextInQueue() throws InterruptedException {
+    boolean acquired =
+        this.numRequestsAllowed.tryAcquire(1, this.waitTimeoutInMillis, TimeUnit.MILLISECONDS);
+    if (!acquired) {
+      return false;
+    }
+    this.activeRequests.addAndGet(1);
+    return true;
+  }
+
+  private void exitFromQueue() {
+    this.numRequestsAllowed.release(1);
+    this.activeRequests.addAndGet(-1);
+  }
+
+  private void release() {
+    if (this.activeRequests.get() > this.totalAllowedRequests) {
+      // priority one request is waiting, let's inform it
+      this.exitFromQueue();
+    } else {
+      // next priority
+      CountDownLatch waiter = this.waitingList.poll();
+      if (waiter != null) {
+        waiter.countDown();
+      }
+      this.exitFromQueue();
+    }
+  }
+
+  @Override
+  public SlotReservation allowSlotBorrowing() throws InterruptedException {
+    // if we reach here that means slot is not available
+    return null;
+  }
+
+  public int getRequestsAllowed() {
+    return this.activeRequests.get();
+  }
+
+  private RequestPriorities getRequestPriority(HttpServletRequest request) {
+    String requestPriority = request.getHeader(SOLR_REQUEST_PRIORITY_PARAM);
+    try {
+      return RequestPriorities.valueOf(requestPriority);
+    } catch (IllegalArgumentException iae) {
+    }
+    return null;
+  }
+
+  public enum RequestPriorities {
+    // this has high priority
+    FOREGROUND,
+    // this has low priority
+    BACKGROUND
+  }
+}

solr/core/src/java/org/apache/solr/servlet/QueryRateLimiter.java

@@ -17,20 +17,12 @@
 
 package org.apache.solr.servlet;
 
-import static org.apache.solr.core.RateLimiterConfig.RL_CONFIG_KEY;
-
 import com.fasterxml.jackson.databind.ObjectMapper;
 import java.io.IOException;
-import java.util.Map;
 import org.apache.solr.client.solrj.SolrRequest;
 import org.apache.solr.client.solrj.request.beans.RateLimiterPayload;
-import org.apache.solr.common.cloud.SolrZkClient;
-import org.apache.solr.common.cloud.ZkStateReader;
-import org.apache.solr.common.util.Utils;
 import org.apache.solr.core.RateLimiterConfig;
 import org.apache.solr.util.SolrJacksonAnnotationInspector;
-import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.data.Stat;
 
 /**
  * Implementation of RequestRateLimiter specific to query request types. Most of the actual work is
@@ -39,26 +31,17 @@
 public class QueryRateLimiter extends RequestRateLimiter {
   private static final ObjectMapper mapper = SolrJacksonAnnotationInspector.createObjectMapper();
 
-  public QueryRateLimiter(SolrZkClient solrZkClient) {
-    super(constructQueryRateLimiterConfig(solrZkClient));
-  }
-
   public QueryRateLimiter(RateLimiterConfig config) {
     super(config);
   }
 
   public static RateLimiterConfig processConfigChange(
-      SolrRequest.SolrRequestType requestType,
-      RateLimiterConfig rateLimiterConfig,
-      Map<String, Object> properties)
-      throws IOException {
-    byte[] configInput = Utils.toJSON(properties.get(RL_CONFIG_KEY));
+      RateLimiterConfig rateLimiterConfig, RateLimiterPayload rateLimiterMeta) throws IOException {
 
-    RateLimiterPayload rateLimiterMeta;
-    if (configInput == null || configInput.length == 0) {
-      rateLimiterMeta = null;
-    } else {
-      rateLimiterMeta = mapper.readValue(configInput, RateLimiterPayload.class);
+    // default rate limiter
+    SolrRequest.SolrRequestType requestType = SolrRequest.SolrRequestType.QUERY;
+    if (rateLimiterMeta.priorityBasedEnabled) {
+      requestType = SolrRequest.SolrRequestType.PRIORITY_BASED;
     }
 
     if (rateLimiterConfig == null || rateLimiterConfig.shouldUpdate(rateLimiterMeta)) {
@@ -68,37 +51,4 @@ public static RateLimiterConfig processConfigChange(
       return null;
     }
   }
-
-  // To be used in initialization
-  @SuppressWarnings({"unchecked"})
-  private static RateLimiterConfig constructQueryRateLimiterConfig(SolrZkClient zkClient) {
-    try {
-
-      if (zkClient == null) {
-        return new RateLimiterConfig(SolrRequest.SolrRequestType.QUERY);
-      }
-
-      Map<String, Object> clusterPropsJson =
-          (Map<String, Object>)
-              Utils.fromJSON(zkClient.getData(ZkStateReader.CLUSTER_PROPS, null, new Stat(), true));
-      byte[] configInput = Utils.toJSON(clusterPropsJson.get(RL_CONFIG_KEY));
-
-      if (configInput.length == 0) {
-        // No Rate Limiter configuration defined in clusterprops.json. Return default configuration
-        // values
-        return new RateLimiterConfig(SolrRequest.SolrRequestType.QUERY);
-      }
-
-      RateLimiterPayload rateLimiterMeta = mapper.readValue(configInput, RateLimiterPayload.class);
-
-      return new RateLimiterConfig(SolrRequest.SolrRequestType.QUERY, rateLimiterMeta);
-    } catch (KeeperException.NoNodeException e) {
-      return new RateLimiterConfig(SolrRequest.SolrRequestType.QUERY);
-    } catch (KeeperException | InterruptedException e) {
-      throw new RuntimeException(
-          "Error reading cluster property", SolrZkClient.checkInterrupted(e));
-    } catch (IOException e) {
-      throw new RuntimeException("Encountered an IOException " + e.getMessage());
-    }
-  }
 }