IndicesClusterStateService should replace an init. replica with an in…

…it. primary with the same aId (#32374)

In rare cases it is possible that a nodes gets an instruction to replace a replica
shard that's in `POST_RECOVERY` with a new initializing primary with the same allocation id.
This can happen by batching cluster states that include the starting of the replica, with
closing of the indices, opening it up again and allocating the primary shard to the node in
question. The node should then clean it's initializing replica and replace it with a new
initializing primary.

I'm not sure whether the test I added really adds enough value as existing tests found this. The main reason I added is to allow for simpler reproduction and to double check I fixed it. I'm open to discuss if we should keep.

Closes #32308

server/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java

@@ -420,6 +420,12 @@ private void removeShards(final ClusterState state) {
                     // state may result in a new shard being initialized while having the same allocation id as the currently started shard.
                     logger.debug("{} removing shard (not active, current {}, new {})", shardId, currentRoutingEntry, newShardRouting);
                     indexService.removeShard(shardId.id(), "removing shard (stale copy)");
+                } else if (newShardRouting.primary() && currentRoutingEntry.primary() == false && newShardRouting.initializing()) {
+                    assert currentRoutingEntry.initializing() : currentRoutingEntry; // see above if clause
+                    // this can happen when cluster state batching batches activation of the shard, closing an index, reopening it
+                    // and assigning an initializing primary to this node
+                    logger.debug("{} removing shard (not active, current {}, new {})", shardId, currentRoutingEntry, newShardRouting);
+                    indexService.removeShard(shardId.id(), "removing shard (stale copy)");
                 }
             }
         }

server/src/test/java/org/elasticsearch/action/support/replication/ClusterStateCreationUtils.java

@@ -27,10 +27,12 @@
 import org.elasticsearch.cluster.metadata.MetaData;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
+import org.elasticsearch.cluster.routing.AllocationId;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
 import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
 import org.elasticsearch.cluster.routing.RoutingTable;
 import org.elasticsearch.cluster.routing.RoutingTable.Builder;
+import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.ShardRoutingState;
 import org.elasticsearch.cluster.routing.TestShardRouting;
 import org.elasticsearch.cluster.routing.UnassignedInfo;
@@ -44,6 +46,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_CREATION_DATE;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
@@ -93,7 +96,8 @@ public static ClusterState state(String index, boolean activePrimaryLocal, Shard
         IndexMetaData indexMetaData = IndexMetaData.builder(index).settings(Settings.builder()
                 .put(SETTING_VERSION_CREATED, Version.CURRENT)
                 .put(SETTING_NUMBER_OF_SHARDS, 1).put(SETTING_NUMBER_OF_REPLICAS, numberOfReplicas)
-                .put(SETTING_CREATION_DATE, System.currentTimeMillis())).primaryTerm(0, primaryTerm).build();
+                .put(SETTING_CREATION_DATE, System.currentTimeMillis())).primaryTerm(0, primaryTerm)
+            .build();
 
         RoutingTable.Builder routing = new RoutingTable.Builder();
         routing.addAsNew(indexMetaData);
@@ -138,12 +142,19 @@ public static ClusterState state(String index, boolean activePrimaryLocal, Shard
                     TestShardRouting.newShardRouting(index, shardId.id(), replicaNode, relocatingNode, false, replicaState,
                             unassignedInfo));
         }
+        final IndexShardRoutingTable indexShardRoutingTable = indexShardRoutingBuilder.build();
+
+        IndexMetaData.Builder indexMetaDataBuilder = new IndexMetaData.Builder(indexMetaData);
+        indexMetaDataBuilder.putInSyncAllocationIds(0,
+            indexShardRoutingTable.activeShards().stream().map(ShardRouting::allocationId).map(AllocationId::getId)
+            .collect(Collectors.toSet())
+        );
 
         ClusterState.Builder state = ClusterState.builder(new ClusterName("test"));
         state.nodes(discoBuilder);
-        state.metaData(MetaData.builder().put(indexMetaData, false).generateClusterUuidIfNeeded());
+        state.metaData(MetaData.builder().put(indexMetaDataBuilder.build(), false).generateClusterUuidIfNeeded());
         state.routingTable(RoutingTable.builder().add(IndexRoutingTable.builder(indexMetaData.getIndex())
-                .addIndexShard(indexShardRoutingBuilder.build())).build());
+                .addIndexShard(indexShardRoutingTable)).build());
         return state.build();
     }
 
@@ -272,21 +283,21 @@ public static ClusterState stateWithAssignedPrimariesAndOneReplica(String index,
         state.routingTable(RoutingTable.builder().add(indexRoutingTableBuilder.build()).build());
         return state.build();
     }
-    
-    
+
+
     /**
      * Creates cluster state with several indexes, shards and replicas and all shards STARTED.
      */
     public static ClusterState stateWithAssignedPrimariesAndReplicas(String[] indices, int numberOfShards, int numberOfReplicas) {
 
-        int numberOfDataNodes = numberOfReplicas + 1; 
+        int numberOfDataNodes = numberOfReplicas + 1;
         DiscoveryNodes.Builder discoBuilder = DiscoveryNodes.builder();
         for (int i = 0; i < numberOfDataNodes + 1; i++) {
             final DiscoveryNode node = newNode(i);
             discoBuilder = discoBuilder.add(node);
         }
         discoBuilder.localNodeId(newNode(0).getId());
-        discoBuilder.masterNodeId(newNode(numberOfDataNodes + 1).getId()); 
+        discoBuilder.masterNodeId(newNode(numberOfDataNodes + 1).getId());
         ClusterState.Builder state = ClusterState.builder(new ClusterName("test"));
         state.nodes(discoBuilder);
         Builder routingTableBuilder = RoutingTable.builder();
@@ -316,7 +327,7 @@ public static ClusterState stateWithAssignedPrimariesAndReplicas(String[] indice
         state.metaData(metadataBuilder);
         state.routingTable(routingTableBuilder.build());
         return state.build();
-    }    
+    }
 
     /**
      * Creates cluster state with and index that has one shard and as many replicas as numberOfReplicas.

server/src/test/java/org/elasticsearch/indices/cluster/AbstractIndicesClusterStateServiceTestCase.java

@@ -74,6 +74,10 @@ public void injectRandomFailures() {
         enableRandomFailures = randomBoolean();
     }
 
+    protected void disableRandomFailures() {
+        enableRandomFailures = false;
+    }
+
     protected void failRandomly() {
         if (enableRandomFailures && rarely()) {
             throw new RuntimeException("dummy test failure");

server/src/test/java/org/elasticsearch/indices/cluster/IndicesClusterStateServiceRandomUpdatesTests.java

@@ -49,6 +49,7 @@
 import org.elasticsearch.discovery.DiscoverySettings;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.shard.PrimaryReplicaSyncer;
+import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.indices.recovery.PeerRecoveryTargetService;
 import org.elasticsearch.repositories.RepositoriesService;
 import org.elasticsearch.threadpool.TestThreadPool;
@@ -75,6 +76,7 @@
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_SHARDS;
 import static org.elasticsearch.cluster.routing.ShardRoutingState.INITIALIZING;
+import static org.hamcrest.Matchers.equalTo;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -198,6 +200,59 @@ public void testJoiningNewClusterOnlyRemovesInMemoryIndexStructures() {
         }
     }
 
+    /**
+     * In rare cases it is possible that a nodes gets an instruction to replace a replica
+     * shard that's in POST_RECOVERY with a new initializing primary with the same allocation id.
+     * This can happen by batching cluster states that include the starting of the replica, with
+     * closing of the indices, opening it up again and allocating the primary shard to the node in
+     * question. The node should then clean it's initializing replica and replace it with a new
+     * initializing primary.
+     */
+    public void testInitializingPrimaryRemovesInitializingReplicaWithSameAID() {
+        disableRandomFailures();
+        String index = "index_" + randomAlphaOfLength(8).toLowerCase(Locale.ROOT);
+        ClusterState state = ClusterStateCreationUtils.state(index, randomBoolean(),
+            ShardRoutingState.STARTED, ShardRoutingState.INITIALIZING);
+
+        // the initial state which is derived from the newly created cluster state but doesn't contain the index
+        ClusterState previousState = ClusterState.builder(state)
+            .metaData(MetaData.builder(state.metaData()).remove(index))
+            .routingTable(RoutingTable.builder().build())
+            .build();
+
+        // pick a data node to simulate the adding an index cluster state change event on, that has shards assigned to it
+        final ShardRouting shardRouting = state.routingTable().index(index).shard(0).replicaShards().get(0);
+        final ShardId shardId = shardRouting.shardId();
+        DiscoveryNode node = state.nodes().get(shardRouting.currentNodeId());
+
+        // simulate the cluster state change on the node
+        ClusterState localState = adaptClusterStateToLocalNode(state, node);
+        ClusterState previousLocalState = adaptClusterStateToLocalNode(previousState, node);
+        IndicesClusterStateService indicesCSSvc = createIndicesClusterStateService(node, RecordingIndicesService::new);
+        indicesCSSvc.start();
+        indicesCSSvc.applyClusterState(new ClusterChangedEvent("cluster state change that adds the index", localState, previousLocalState));
+        previousState = state;
+
+        // start the replica
+        state = cluster.applyStartedShards(state, state.routingTable().index(index).shard(0).replicaShards());
+
+        // close the index and open it up again (this will sometimes swap roles between primary and replica)
+        CloseIndexRequest closeIndexRequest = new CloseIndexRequest(state.metaData().index(index).getIndex().getName());
+        state = cluster.closeIndices(state, closeIndexRequest);
+        OpenIndexRequest openIndexRequest = new OpenIndexRequest(state.metaData().index(index).getIndex().getName());
+        state = cluster.openIndices(state, openIndexRequest);
+
+        localState = adaptClusterStateToLocalNode(state, node);
+        previousLocalState = adaptClusterStateToLocalNode(previousState, node);
+
+        indicesCSSvc.applyClusterState(new ClusterChangedEvent("new cluster state", localState, previousLocalState));
+
+        final MockIndexShard shardOrNull = ((RecordingIndicesService) indicesCSSvc.indicesService).getShardOrNull(shardId);
+        assertThat(shardOrNull == null ? null : shardOrNull.routingEntry(),
+            equalTo(state.getRoutingNodes().node(node.getId()).getByShardId(shardId)));
+
+    }
+
     public ClusterState randomInitialClusterState(Map<DiscoveryNode, IndicesClusterStateService> clusterStateServiceMap,
                                                   Supplier<MockIndicesService> indicesServiceSupplier) {
         List<DiscoveryNode> allNodes = new ArrayList<>();