[Backport 2.16] Make reroute iteration time-bound for large shard allocations

CHANGELOG.md

@@ -60,6 +60,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Allow @InternalApi annotation on classes not meant to be constructed outside of the OpenSearch core ([#14575](https://github.com/opensearch-project/OpenSearch/pull/14575))
 - Add @InternalApi annotation to japicmp exclusions ([#14597](https://github.com/opensearch-project/OpenSearch/pull/14597))
 - Allow system index warning in OpenSearchRestTestCase.refreshAllIndices ([#14635](https://github.com/opensearch-project/OpenSearch/pull/14635))
+- Make reroute iteration time-bound for large shard allocations ([#14848](https://github.com/opensearch-project/OpenSearch/pull/14848))
 
 ### Deprecated
 - Deprecate batch_size parameter on bulk API ([#14725](https://github.com/opensearch-project/OpenSearch/pull/14725))

server/src/internalClusterTest/java/org/opensearch/gateway/RecoveryFromGatewayIT.java

@@ -769,7 +769,7 @@ public void testMessyElectionsStillMakeClusterGoGreen() throws Exception {
         ensureGreen("test");
     }
 
-    public void testBatchModeEnabled() throws Exception {
+    public void testBatchModeEnabledWithoutTimeout() throws Exception {
         internalCluster().startClusterManagerOnlyNodes(
             1,
             Settings.builder().put(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.getKey(), true).build()
@@ -810,6 +810,132 @@ public void testBatchModeEnabled() throws Exception {
         assertEquals(0, gatewayAllocator.getNumberOfInFlightFetches());
     }
 
+    public void testBatchModeEnabledWithSufficientTimeoutAndClusterGreen() throws Exception {
+        internalCluster().startClusterManagerOnlyNodes(
+            1,
+            Settings.builder()
+                .put(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.getKey(), true)
+                .put(ShardsBatchGatewayAllocator.PRIMARY_BATCH_ALLOCATOR_TIMEOUT_SETTING.getKey(), "20s")
+                .put(ShardsBatchGatewayAllocator.REPLICA_BATCH_ALLOCATOR_TIMEOUT_SETTING.getKey(), "20s")
+                .build()
+        );
+        List<String> dataOnlyNodes = internalCluster().startDataOnlyNodes(2);
+        createIndex(
+            "test",
+            Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1).put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 1).build()
+        );
+        ensureGreen("test");
+        Settings node0DataPathSettings = internalCluster().dataPathSettings(dataOnlyNodes.get(0));
+        Settings node1DataPathSettings = internalCluster().dataPathSettings(dataOnlyNodes.get(1));
+        internalCluster().stopRandomNode(InternalTestCluster.nameFilter(dataOnlyNodes.get(0)));
+        internalCluster().stopRandomNode(InternalTestCluster.nameFilter(dataOnlyNodes.get(1)));
+        ensureRed("test");
+        ensureStableCluster(1);
+
+        logger.info("--> Now do a protective reroute");
+        ClusterRerouteResponse clusterRerouteResponse = client().admin().cluster().prepareReroute().setRetryFailed(true).get();
+        assertTrue(clusterRerouteResponse.isAcknowledged());
+
+        ShardsBatchGatewayAllocator gatewayAllocator = internalCluster().getInstance(
+            ShardsBatchGatewayAllocator.class,
+            internalCluster().getClusterManagerName()
+        );
+        assertTrue(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.get(internalCluster().clusterService().getSettings()));
+        assertEquals(1, gatewayAllocator.getNumberOfStartedShardBatches());
+        assertEquals(1, gatewayAllocator.getNumberOfStoreShardBatches());
+
+        // Now start both data nodes and ensure batch mode is working
+        logger.info("--> restarting the stopped nodes");
+        internalCluster().startDataOnlyNode(Settings.builder().put("node.name", dataOnlyNodes.get(0)).put(node0DataPathSettings).build());
+        internalCluster().startDataOnlyNode(Settings.builder().put("node.name", dataOnlyNodes.get(1)).put(node1DataPathSettings).build());
+        ensureStableCluster(3);
+        ensureGreen("test");
+        assertEquals(0, gatewayAllocator.getNumberOfStartedShardBatches());
+        assertEquals(0, gatewayAllocator.getNumberOfStoreShardBatches());
+        assertEquals(0, gatewayAllocator.getNumberOfInFlightFetches());
+    }
+
+    public void testBatchModeEnabledWithInSufficientTimeoutButClusterGreen() throws Exception {
+
+        internalCluster().startClusterManagerOnlyNodes(
+            1,
+            Settings.builder().put(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.getKey(), true).build()
+        );
+        List<String> dataOnlyNodes = internalCluster().startDataOnlyNodes(2);
+        createNIndices(50, "test"); // this will create 50p, 50r shards
+        ensureStableCluster(3);
+        IndicesStatsResponse indicesStats = dataNodeClient().admin().indices().prepareStats().get();
+        assertThat(indicesStats.getSuccessfulShards(), equalTo(100));
+        ClusterHealthResponse health = client().admin()
+            .cluster()
+            .health(Requests.clusterHealthRequest().waitForGreenStatus().timeout("1m"))
+            .actionGet();
+        assertFalse(health.isTimedOut());
+        assertEquals(GREEN, health.getStatus());
+
+        String clusterManagerName = internalCluster().getClusterManagerName();
+        Settings clusterManagerDataPathSettings = internalCluster().dataPathSettings(clusterManagerName);
+        Settings node0DataPathSettings = internalCluster().dataPathSettings(dataOnlyNodes.get(0));
+        Settings node1DataPathSettings = internalCluster().dataPathSettings(dataOnlyNodes.get(1));
+
+        internalCluster().stopCurrentClusterManagerNode();
+        internalCluster().stopRandomNode(InternalTestCluster.nameFilter(dataOnlyNodes.get(0)));
+        internalCluster().stopRandomNode(InternalTestCluster.nameFilter(dataOnlyNodes.get(1)));
+
+        // Now start cluster manager node and post that verify batches created
+        internalCluster().startClusterManagerOnlyNodes(
+            1,
+            Settings.builder()
+                .put("node.name", clusterManagerName)
+                .put(clusterManagerDataPathSettings)
+                .put(ShardsBatchGatewayAllocator.GATEWAY_ALLOCATOR_BATCH_SIZE.getKey(), 5)
+                .put(ShardsBatchGatewayAllocator.PRIMARY_BATCH_ALLOCATOR_TIMEOUT_SETTING.getKey(), "10ms")
+                .put(ShardsBatchGatewayAllocator.REPLICA_BATCH_ALLOCATOR_TIMEOUT_SETTING.getKey(), "10ms")
+                .put(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.getKey(), true)
+                .build()
+        );
+        ensureStableCluster(1);
+
+        logger.info("--> Now do a protective reroute"); // to avoid any race condition in test
+        ClusterRerouteResponse clusterRerouteResponse = client().admin().cluster().prepareReroute().setRetryFailed(true).get();
+        assertTrue(clusterRerouteResponse.isAcknowledged());
+
+        ShardsBatchGatewayAllocator gatewayAllocator = internalCluster().getInstance(
+            ShardsBatchGatewayAllocator.class,
+            internalCluster().getClusterManagerName()
+        );
+
+        assertTrue(ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_BATCH_MODE.get(internalCluster().clusterService().getSettings()));
+        assertEquals(10, gatewayAllocator.getNumberOfStartedShardBatches());
+        assertEquals(10, gatewayAllocator.getNumberOfStoreShardBatches());
+        health = client(internalCluster().getClusterManagerName()).admin().cluster().health(Requests.clusterHealthRequest()).actionGet();
+        assertFalse(health.isTimedOut());
+        assertEquals(RED, health.getStatus());
+        assertEquals(100, health.getUnassignedShards());
+        assertEquals(0, health.getInitializingShards());
+        assertEquals(0, health.getActiveShards());
+        assertEquals(0, health.getRelocatingShards());
+        assertEquals(0, health.getNumberOfDataNodes());
+
+        // Now start both data nodes and ensure batch mode is working
+        logger.info("--> restarting the stopped nodes");
+        internalCluster().startDataOnlyNode(Settings.builder().put("node.name", dataOnlyNodes.get(0)).put(node0DataPathSettings).build());
+        internalCluster().startDataOnlyNode(Settings.builder().put("node.name", dataOnlyNodes.get(1)).put(node1DataPathSettings).build());
+        ensureStableCluster(3);
+
+        // wait for cluster to turn green
+        health = client().admin().cluster().health(Requests.clusterHealthRequest().waitForGreenStatus().timeout("5m")).actionGet();
+        assertFalse(health.isTimedOut());
+        assertEquals(GREEN, health.getStatus());
+        assertEquals(0, health.getUnassignedShards());
+        assertEquals(0, health.getInitializingShards());
+        assertEquals(100, health.getActiveShards());
+        assertEquals(0, health.getRelocatingShards());
+        assertEquals(2, health.getNumberOfDataNodes());
+        assertEquals(0, gatewayAllocator.getNumberOfStartedShardBatches());
+        assertEquals(0, gatewayAllocator.getNumberOfStoreShardBatches());
+    }
+
     public void testBatchModeDisabled() throws Exception {
         internalCluster().startClusterManagerOnlyNodes(
             1,

server/src/main/java/org/opensearch/cluster/routing/allocation/AllocationService.java

@@ -72,6 +72,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -617,10 +618,10 @@
 
     private void allocateAllUnassignedShards(RoutingAllocation allocation) {
         ExistingShardsAllocator allocator = existingShardsAllocators.get(ShardsBatchGatewayAllocator.ALLOCATOR_NAME);
-        allocator.allocateAllUnassignedShards(allocation, true);
+        Optional.ofNullable(allocator.allocateAllUnassignedShards(allocation, true)).ifPresent(Runnable::run);
         allocator.afterPrimariesBeforeReplicas(allocation);
         // Replicas Assignment
-        allocator.allocateAllUnassignedShards(allocation, false);
+        Optional.ofNullable(allocator.allocateAllUnassignedShards(allocation, false)).ifPresent(Runnable::run);
     }
 
     private void disassociateDeadNodes(RoutingAllocation allocation) {

server/src/main/java/org/opensearch/cluster/routing/allocation/ExistingShardsAllocator.java

@@ -41,6 +41,7 @@
 import org.opensearch.gateway.GatewayAllocator;
 import org.opensearch.gateway.ShardsBatchGatewayAllocator;
 
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -108,14 +109,16 @@ void allocateUnassigned(
      *
      * Allocation service will currently run the default implementation of it implemented by {@link ShardsBatchGatewayAllocator}
      */
-    default void allocateAllUnassignedShards(RoutingAllocation allocation, boolean primary) {
+    default Runnable allocateAllUnassignedShards(RoutingAllocation allocation, boolean primary) {
         RoutingNodes.UnassignedShards.UnassignedIterator iterator = allocation.routingNodes().unassigned().iterator();
+        List<Runnable> runnables = new ArrayList<>();
         while (iterator.hasNext()) {
             ShardRouting shardRouting = iterator.next();
             if (shardRouting.primary() == primary) {
-                allocateUnassigned(shardRouting, allocation, iterator);
+                runnables.add(() -> allocateUnassigned(shardRouting, allocation, iterator));
             }
         }
+        return () -> runnables.forEach(Runnable::run);
     }
 
     /**

server/src/main/java/org/opensearch/common/settings/ClusterSettings.java

@@ -343,6 +343,8 @@ public void apply(Settings value, Settings current, Settings previous) {
                 GatewayService.RECOVER_AFTER_NODES_SETTING,
                 GatewayService.RECOVER_AFTER_TIME_SETTING,
                 ShardsBatchGatewayAllocator.GATEWAY_ALLOCATOR_BATCH_SIZE,
+                ShardsBatchGatewayAllocator.PRIMARY_BATCH_ALLOCATOR_TIMEOUT_SETTING,
+                ShardsBatchGatewayAllocator.REPLICA_BATCH_ALLOCATOR_TIMEOUT_SETTING,
                 PersistedClusterStateService.SLOW_WRITE_LOGGING_THRESHOLD,
                 NetworkModule.HTTP_DEFAULT_TYPE_SETTING,
                 NetworkModule.TRANSPORT_DEFAULT_TYPE_SETTING,

server/src/main/java/org/opensearch/common/util/BatchRunnableExecutor.java

@@ -0,0 +1,66 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.util;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.opensearch.common.Randomness;
+import org.opensearch.common.unit.TimeValue;
+import org.opensearch.common.util.concurrent.TimeoutAwareRunnable;
+
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+/**
+ * A {@link Runnable} that iteratively executes a batch of {@link TimeoutAwareRunnable}s. If the elapsed time exceeds the timeout defined by {@link TimeValue} timeout, then all subsequent {@link TimeoutAwareRunnable}s will have their {@link TimeoutAwareRunnable#onTimeout} method invoked and will not be run.
+ *
+ * @opensearch.internal
+ */
+public class BatchRunnableExecutor implements Runnable {
+
+    private final Supplier<TimeValue> timeoutSupplier;
+
+    private final List<TimeoutAwareRunnable> timeoutAwareRunnables;
+
+    private static final Logger logger = LogManager.getLogger(BatchRunnableExecutor.class);
+
+    public BatchRunnableExecutor(List<TimeoutAwareRunnable> timeoutAwareRunnables, Supplier<TimeValue> timeoutSupplier) {
+        this.timeoutSupplier = timeoutSupplier;
+        this.timeoutAwareRunnables = timeoutAwareRunnables;
+    }
+
+    // for tests
+    public List<TimeoutAwareRunnable> getTimeoutAwareRunnables() {
+        return this.timeoutAwareRunnables;
+    }
+
+    @Override
+    public void run() {
+        logger.debug("Starting execution of runnable of size [{}]", timeoutAwareRunnables.size());
+        long startTime = System.nanoTime();
+        if (timeoutAwareRunnables.isEmpty()) {
+            return;
+        }
+        Randomness.shuffle(timeoutAwareRunnables);
+        for (TimeoutAwareRunnable runnable : timeoutAwareRunnables) {
+            if (timeoutSupplier.get().nanos() < 0 || System.nanoTime() - startTime < timeoutSupplier.get().nanos()) {
+                runnable.run();
+            } else {
+                logger.debug("Executing timeout for runnable of size [{}]", timeoutAwareRunnables.size());
+                runnable.onTimeout();
+            }
+        }
+        logger.debug(
+            "Time taken to execute timed runnables in this cycle:[{}ms]",
+            TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime)
+        );
+    }
+
+}

server/src/main/java/org/opensearch/common/util/concurrent/TimeoutAwareRunnable.java

@@ -0,0 +1,19 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.util.concurrent;
+
+/**
+ * Runnable that is aware of a timeout
+ *
+ * @opensearch.internal
+ */
+public interface TimeoutAwareRunnable extends Runnable {
+
+    void onTimeout();
+}

server/src/main/java/org/opensearch/gateway/BaseGatewayShardAllocator.java

@@ -36,16 +36,20 @@
 import org.apache.logging.log4j.Logger;
 import org.opensearch.cluster.routing.RecoverySource;
 import org.opensearch.cluster.routing.RoutingNode;
+import org.opensearch.cluster.routing.RoutingNodes;
 import org.opensearch.cluster.routing.ShardRouting;
 import org.opensearch.cluster.routing.allocation.AllocateUnassignedDecision;
 import org.opensearch.cluster.routing.allocation.AllocationDecision;
 import org.opensearch.cluster.routing.allocation.ExistingShardsAllocator;
 import org.opensearch.cluster.routing.allocation.NodeAllocationResult;
 import org.opensearch.cluster.routing.allocation.RoutingAllocation;
 import org.opensearch.cluster.routing.allocation.decider.Decision;
+import org.opensearch.core.index.shard.ShardId;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 /**
  * An abstract class that implements basic functionality for allocating
@@ -78,6 +82,23 @@ public void allocateUnassigned(
         executeDecision(shardRouting, allocateUnassignedDecision, allocation, unassignedAllocationHandler);
     }
 
+    protected void allocateUnassignedBatchOnTimeout(List<ShardRouting> shardRoutings, RoutingAllocation allocation, boolean primary) {
+        Set<ShardId> shardIdsFromBatch = new HashSet<>();
+        for (ShardRouting shardRouting : shardRoutings) {
+            ShardId shardId = shardRouting.shardId();
+            shardIdsFromBatch.add(shardId);
+        }
+        RoutingNodes.UnassignedShards.UnassignedIterator iterator = allocation.routingNodes().unassigned().iterator();
+        while (iterator.hasNext()) {
+            ShardRouting unassignedShard = iterator.next();
+            AllocateUnassignedDecision allocationDecision;
+            if (unassignedShard.primary() == primary && shardIdsFromBatch.contains(unassignedShard.shardId())) {
+                allocationDecision = AllocateUnassignedDecision.throttle(null);
+                executeDecision(unassignedShard, allocationDecision, allocation, iterator);
+            }
+        }
+    }
+
     protected void executeDecision(
         ShardRouting shardRouting,
         AllocateUnassignedDecision allocateUnassignedDecision,