Wait for all Rec. to Stop on Node Close

server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoverySourceService.java

@@ -24,10 +24,13 @@
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.support.ChannelActionListener;
+import org.elasticsearch.action.support.PlainActionFuture;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.common.Nullable;
+import org.elasticsearch.common.component.AbstractLifecycleComponent;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.util.concurrent.FutureUtils;
 import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.shard.IndexEventListener;
 import org.elasticsearch.index.shard.IndexShard;
@@ -50,7 +53,7 @@
  * The source recovery accepts recovery requests from other peer shards and start the recovery process from this
  * source shard to the target shard.
  */
-public class PeerRecoverySourceService implements IndexEventListener {
+public class PeerRecoverySourceService extends AbstractLifecycleComponent implements IndexEventListener {
 
     private static final Logger logger = LogManager.getLogger(PeerRecoverySourceService.class);
 
@@ -74,6 +77,19 @@ public PeerRecoverySourceService(TransportService transportService, IndicesServi
             new StartRecoveryTransportRequestHandler());
     }
 
+    @Override
+    protected void doStart() {
+    }
+
+    @Override
+    protected void doStop() {
+        ongoingRecoveries.awaitEmpty();
+    }
+
+    @Override
+    protected void doClose() {
+    }
+
     @Override
     public void beforeIndexShardClosed(ShardId shardId, @Nullable IndexShard indexShard,
                                        Settings indexSettings) {
@@ -118,8 +134,11 @@ final int numberOfOngoingRecoveries() {
     }
 
     final class OngoingRecoveries {
+
         private final Map<IndexShard, ShardRecoveryContext> ongoingRecoveries = new HashMap<>();
 
+        private List<ActionListener<Void>> emptyListeners = new ArrayList<>();
+
         synchronized RecoverySourceHandler addNewRecovery(StartRecoveryRequest request, IndexShard shard) {
             final ShardRecoveryContext shardContext = ongoingRecoveries.computeIfAbsent(shard, s -> new ShardRecoveryContext());
             RecoverySourceHandler handler = shardContext.addNewRecovery(request, shard);
@@ -138,6 +157,13 @@ synchronized void remove(IndexShard shard, RecoverySourceHandler handler) {
             if (shardRecoveryContext.recoveryHandlers.isEmpty()) {
                 ongoingRecoveries.remove(shard);
             }
+            if (ongoingRecoveries.isEmpty()) {
+                if (emptyListeners != null) {
+                    final List<ActionListener<Void>> onEmptyListeners = emptyListeners;
+                    emptyListeners = null;
+                    ActionListener.onResponse(onEmptyListeners, null);
+                }
+            }
         }
 
         synchronized void cancel(IndexShard shard, String reason) {
@@ -157,6 +183,22 @@ synchronized void cancel(IndexShard shard, String reason) {
             }
         }
 
+        void awaitEmpty() {
+            assert lifecycle.stoppedOrClosed();
+            final PlainActionFuture<Void> future;
+            synchronized (this) {
+                if (ongoingRecoveries.isEmpty()) {
+                    return;
+                }
+                future = new PlainActionFuture<>();
+                if (emptyListeners == null) {
+                    emptyListeners = new ArrayList<>();
+                }
+                emptyListeners.add(future);
+            }
+            FutureUtils.get(future);
+        }
+
         private final class ShardRecoveryContext {
             final Set<RecoverySourceHandler> recoveryHandlers = new HashSet<>();
 

server/src/main/java/org/elasticsearch/indices/recovery/RecoverySourceHandler.java

@@ -402,13 +402,14 @@ private Releasable acquireStore(Store store) {
         store.incRef();
         return Releasables.releaseOnce(() -> {
             final PlainActionFuture<Void> future = new PlainActionFuture<>();
-            threadPool.generic().execute(new ActionRunnable<>(future) {
-                @Override
-                protected void doRun() {
-                    store.decRef();
-                    listener.onResponse(null);
-                }
-            });
+            assert threadPool.generic().isShutdown() == false;
+            // TODO: We shouldn't use the generic thread pool here as we already execute this from the generic pool.
+            //       While practically unlikely at a min pool size of 128 we could technically block the whole pool by waiting on futures
+            //       below and thus make it impossible for the store release to execute which in turn would block the futures forever
+            threadPool.generic().execute(ActionRunnable.wrap(future, l -> {
+                store.decRef();
+                l.onResponse(null);
+            }));
             FutureUtils.get(future);
         });
     }

server/src/main/java/org/elasticsearch/node/Node.java

@@ -592,6 +592,7 @@ protected Node(
                 .filter(p -> p instanceof LifecycleComponent)
                 .map(p -> (LifecycleComponent) p).collect(Collectors.toList());
             resourcesToClose.addAll(pluginLifecycleComponents);
+            resourcesToClose.add(injector.getInstance(PeerRecoverySourceService.class));
             this.pluginLifecycleComponents = Collections.unmodifiableList(pluginLifecycleComponents);
             client.initialize(injector.getInstance(new Key<Map<ActionType, TransportAction>>() {}), transportService.getTaskManager(),
                     () -> clusterService.localNode().getId(), transportService.getRemoteClusterService());
@@ -688,6 +689,7 @@ public Node start() throws NodeValidationException {
         assert localNodeFactory.getNode() != null;
         assert transportService.getLocalNode().equals(localNodeFactory.getNode())
             : "transportService has a different local node than the factory provided";
+        injector.getInstance(PeerRecoverySourceService.class).start();
         final MetaData onDiskMetadata;
         // we load the global state here (the persistent part of the cluster state stored on disk) to
         // pass it to the bootstrap checks to allow plugins to enforce certain preconditions based on the recovered state.
@@ -833,6 +835,7 @@ public synchronized void close() throws IOException {
         toClose.add(injector.getInstance(IndicesService.class));
         // close filter/fielddata caches after indices
         toClose.add(injector.getInstance(IndicesStore.class));
+        toClose.add(injector.getInstance(PeerRecoverySourceService.class));
         toClose.add(() -> stopWatch.stop().start("cluster"));
         toClose.add(injector.getInstance(ClusterService.class));
         toClose.add(() -> stopWatch.stop().start("node_connections_service"));