Check for closed connection while opening

While opening a connection to a node, a channel can subsequently
close. If this happens, a future callback whose purpose is to close all
other channels and disconnect from the node will fire. However, this
future will not be ready to close all the channels because the
connection will not be exposed to the future callback yet. Since this
callback is run once, we will never try to disconnect from this node
again and we will be left with a closed channel. This commit adds a
check that all channels are open before exposing the channel and throws
a general connection exception. In this case, the usual connection retry
logic will take over.

Relates #26932

core/src/main/java/org/elasticsearch/transport/TcpTransport.java

@@ -599,6 +599,9 @@ public final NodeChannels openConnection(DiscoveryNode node, ConnectionProfile c
                 nodeChannels = new NodeChannels(nodeChannels, version); // clone the channels - we now have the correct version
                 transportService.onConnectionOpened(nodeChannels);
                 connectionRef.set(nodeChannels);
+                if (Arrays.stream(nodeChannels.channels).allMatch(this::isOpen) == false) {
+                    throw new ConnectTransportException(node, "a channel closed while connecting");
+                }
                 success = true;
                 return nodeChannels;
             } catch (ConnectTransportException e) {
@@ -1034,7 +1037,18 @@ protected void innerOnFailure(Exception e) {
      */
     protected abstract void sendMessage(Channel channel, BytesReference reference, ActionListener<Channel> listener);
 
-    protected abstract NodeChannels connectToChannels(DiscoveryNode node, ConnectionProfile connectionProfile,
+    /**
+     * Connect to the node with channels as defined by the specified connection profile. Implementations must invoke the specified channel
+     * close callback when a channel is closed.
+     *
+     * @param node              the node to connect to
+     * @param connectionProfile the connection profile
+     * @param onChannelClose    callback to invoke when a channel is closed
+     * @return the channels
+     * @throws IOException if an I/O exception occurs while opening channels
+     */
+    protected abstract NodeChannels connectToChannels(DiscoveryNode node,
+                                                      ConnectionProfile connectionProfile,
                                                       Consumer<Channel> onChannelClose) throws IOException;
 
     /**

core/src/main/java/org/elasticsearch/transport/TransportService.java

@@ -63,6 +63,7 @@
 import java.util.Objects;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -187,6 +188,15 @@ protected TaskManager createTaskManager() {
         return new TaskManager(settings);
     }
 
+    /**
+     * The executor service for this transport service.
+     *
+     * @return the executor service
+     */
+    protected ExecutorService getExecutorService() {
+        return threadPool.generic();
+    }
+
     void setTracerLogInclude(List<String> tracerLogInclude) {
         this.tracerLogInclude = tracerLogInclude.toArray(Strings.EMPTY_ARRAY);
     }
@@ -232,7 +242,7 @@ protected void doStop() {
                 if (holderToNotify != null) {
                     // callback that an exception happened, but on a different thread since we don't
                     // want handlers to worry about stack overflows
-                    threadPool.generic().execute(new AbstractRunnable() {
+                    getExecutorService().execute(new AbstractRunnable() {
                         @Override
                         public void onRejection(Exception e) {
                             // if we get rejected during node shutdown we don't wanna bubble it up
@@ -879,20 +889,20 @@ void onNodeConnected(final DiscoveryNode node) {
         // connectToNode(); connection is completed successfully
         // addConnectionListener(); this listener shouldn't be called
         final Stream<TransportConnectionListener> listenersToNotify = TransportService.this.connectionListeners.stream();
-        threadPool.generic().execute(() -> listenersToNotify.forEach(listener -> listener.onNodeConnected(node)));
+        getExecutorService().execute(() -> listenersToNotify.forEach(listener -> listener.onNodeConnected(node)));
     }
 
     void onConnectionOpened(Transport.Connection connection) {
         // capture listeners before spawning the background callback so the following pattern won't trigger a call
         // connectToNode(); connection is completed successfully
         // addConnectionListener(); this listener shouldn't be called
         final Stream<TransportConnectionListener> listenersToNotify = TransportService.this.connectionListeners.stream();
-        threadPool.generic().execute(() -> listenersToNotify.forEach(listener -> listener.onConnectionOpened(connection)));
+        getExecutorService().execute(() -> listenersToNotify.forEach(listener -> listener.onConnectionOpened(connection)));
     }
 
     public void onNodeDisconnected(final DiscoveryNode node) {
         try {
-            threadPool.generic().execute( () -> {
+            getExecutorService().execute( () -> {
                 for (final TransportConnectionListener connectionListener : connectionListeners) {
                     connectionListener.onNodeDisconnected(node);
                 }
@@ -911,7 +921,7 @@ void onConnectionClosed(Transport.Connection connection) {
                     if (holderToNotify != null) {
                         // callback that an exception happened, but on a different thread since we don't
                         // want handlers to worry about stack overflows
-                        threadPool.generic().execute(() -> holderToNotify.handler().handleException(new NodeDisconnectedException(
+                        getExecutorService().execute(() -> holderToNotify.handler().handleException(new NodeDisconnectedException(
                             connection.getNode(), holderToNotify.action())));
                     }
                 }

core/src/test/java/org/elasticsearch/transport/TCPTransportTests.java

@@ -224,8 +224,8 @@ protected void sendMessage(Object o, BytesReference reference, ActionListener li
                 }
 
                 @Override
-                protected NodeChannels connectToChannels(DiscoveryNode node, ConnectionProfile profile,
-                                                         Consumer onChannelClose) throws IOException {
+                protected NodeChannels connectToChannels(
+                        DiscoveryNode node, ConnectionProfile profile, Consumer onChannelClose) throws IOException {
                     return new NodeChannels(node, new Object[profile.getNumConnections()], profile);
                 }
 

modules/transport-netty4/src/test/java/org/elasticsearch/transport/netty4/SimpleNetty4TransportTests.java

@@ -52,7 +52,7 @@
 public class SimpleNetty4TransportTests extends AbstractSimpleTransportTestCase {
 
     public static MockTransportService nettyFromThreadPool(Settings settings, ThreadPool threadPool, final Version version,
-            ClusterSettings clusterSettings, boolean doHandshake) {
+                                                           ClusterSettings clusterSettings, boolean doHandshake) {
         NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry(Collections.emptyList());
         Transport transport = new Netty4Transport(settings, threadPool, new NetworkService(Collections.emptyList()),
             BigArrays.NON_RECYCLING_INSTANCE, namedWriteableRegistry, new NoneCircuitBreakerService()) {
@@ -86,6 +86,13 @@ protected MockTransportService build(Settings settings, Version version, Cluster
         return transportService;
     }
 
+    @Override
+    protected void closeConnectionChannel(Transport transport, Transport.Connection connection) throws IOException {
+        final Netty4Transport t = (Netty4Transport) transport;
+        @SuppressWarnings("unchecked") final TcpTransport<Channel>.NodeChannels channels = (TcpTransport<Channel>.NodeChannels) connection;
+        t.closeChannels(channels.getChannels().subList(0, randomIntBetween(1, channels.getChannels().size())), true, false);
+    }
+
     public void testConnectException() throws UnknownHostException {
         try {
             serviceA.connectToNode(new DiscoveryNode("C", new TransportAddress(InetAddress.getByName("localhost"), 9876),
@@ -108,7 +115,8 @@ public void testBindUnavailableAddress() {
             .build();
         ClusterSettings clusterSettings = new ClusterSettings(settings, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
         BindTransportException bindTransportException = expectThrows(BindTransportException.class, () -> {
-            MockTransportService transportService = nettyFromThreadPool(settings, threadPool, Version.CURRENT, clusterSettings, true);
+            MockTransportService transportService =
+                    nettyFromThreadPool(settings, threadPool, Version.CURRENT, clusterSettings, true);
             try {
                 transportService.start();
             } finally {

test/framework/src/main/java/org/elasticsearch/test/transport/MockTransportService.java

@@ -72,6 +72,7 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
@@ -167,6 +168,17 @@ protected TaskManager createTaskManager() {
         }
     }
 
+    private volatile String executorName;
+
+    public void setExecutorName(final String executorName) {
+        this.executorName = executorName;
+    }
+
+    @Override
+    protected ExecutorService getExecutorService() {
+        return executorName == null ? super.getExecutorService() : getThreadPool().executor(executorName);
+    }
+
     /**
      * Clears all the registered rules.
      */

test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java

@@ -83,8 +83,10 @@
 
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.emptySet;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.hasToString;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.startsWith;
@@ -147,14 +149,14 @@ public void onNodeDisconnected(DiscoveryNode node) {
     private MockTransportService buildService(final String name, final Version version, ClusterSettings clusterSettings,
                                               Settings settings, boolean acceptRequests, boolean doHandshake) {
         MockTransportService service = build(
-            Settings.builder()
-                .put(settings)
-                .put(Node.NODE_NAME_SETTING.getKey(), name)
-                .put(TransportService.TRACE_LOG_INCLUDE_SETTING.getKey(), "")
-                .put(TransportService.TRACE_LOG_EXCLUDE_SETTING.getKey(), "NOTHING")
-                .build(),
-            version,
-            clusterSettings, doHandshake);
+                Settings.builder()
+                        .put(settings)
+                        .put(Node.NODE_NAME_SETTING.getKey(), name)
+                        .put(TransportService.TRACE_LOG_INCLUDE_SETTING.getKey(), "")
+                        .put(TransportService.TRACE_LOG_EXCLUDE_SETTING.getKey(), "NOTHING")
+                        .build(),
+                version,
+                clusterSettings, doHandshake);
         if (acceptRequests) {
             service.acceptIncomingRequests();
         }
@@ -2612,4 +2614,33 @@ public void testProfilesIncludesDefault() {
         assertEquals(new HashSet<>(Arrays.asList("default", "test")), profileSettings.stream().map(s -> s.profileName).collect(Collectors
             .toSet()));
     }
+
+    public void testChannelCloseWhileConnecting() throws IOException {
+                try (MockTransportService service = build(Settings.builder().put("name", "close").build(), version0, null, true)) {
+                    service.setExecutorName(ThreadPool.Names.SAME); // make sure stuff is executed in a blocking fashion
+                    service.addConnectionListener(new TransportConnectionListener() {
+                        @Override
+                        public void onConnectionOpened(final Transport.Connection connection) {
+                            try {
+                                closeConnectionChannel(service.getOriginalTransport(), connection);
+                            } catch (final IOException e) {
+                                throw new AssertionError(e);
+                            }
+                        }
+                    });
+                    final ConnectionProfile.Builder builder = new ConnectionProfile.Builder();
+                    builder.addConnections(1,
+                            TransportRequestOptions.Type.BULK,
+                            TransportRequestOptions.Type.PING,
+                            TransportRequestOptions.Type.RECOVERY,
+                            TransportRequestOptions.Type.REG,
+                            TransportRequestOptions.Type.STATE);
+                    final ConnectTransportException e =
+                            expectThrows(ConnectTransportException.class, () -> service.openConnection(nodeA, builder.build()));
+                    assertThat(e, hasToString(containsString(("a channel closed while connecting"))));
+        }
+    }
+
+    protected abstract void closeConnectionChannel(Transport transport, Transport.Connection connection) throws IOException;
+
 }

test/framework/src/main/java/org/elasticsearch/transport/MockTcpTransport.java

@@ -176,7 +176,8 @@ private void readMessage(MockChannel mockChannel, StreamInput input) throws IOEx
     }
 
     @Override
-    protected NodeChannels connectToChannels(DiscoveryNode node, ConnectionProfile profile,
+    protected NodeChannels connectToChannels(DiscoveryNode node,
+                                             ConnectionProfile profile,
                                              Consumer<MockChannel> onChannelClose) throws IOException {
         final MockChannel[] mockChannels = new MockChannel[1];
         final NodeChannels nodeChannels = new NodeChannels(node, mockChannels, LIGHT_PROFILE); // we always use light here

test/framework/src/main/java/org/elasticsearch/transport/nio/NioClient.java

@@ -56,7 +56,9 @@ public NioClient(Logger logger, OpenChannels openChannels, Supplier<SocketSelect
         this.channelFactory = channelFactory;
     }
 
-    public boolean connectToChannels(DiscoveryNode node, NioSocketChannel[] channels, TimeValue connectTimeout,
+    public boolean connectToChannels(DiscoveryNode node,
+                                     NioSocketChannel[] channels,
+                                     TimeValue connectTimeout,
                                      Consumer<NioChannel> closeListener) throws IOException {
         boolean allowedToConnect = semaphore.tryAcquire();
         if (allowedToConnect == false) {

test/framework/src/test/java/org/elasticsearch/transport/MockTcpTransportTests.java

@@ -33,6 +33,7 @@
 import java.util.Collections;
 
 public class MockTcpTransportTests extends AbstractSimpleTransportTestCase {
+
     @Override
     protected MockTransportService build(Settings settings, Version version, ClusterSettings clusterSettings, boolean doHandshake) {
         NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry(Collections.emptyList());
@@ -53,4 +54,13 @@ protected Version executeHandshake(DiscoveryNode node, MockChannel mockChannel,
         mockTransportService.start();
         return mockTransportService;
     }
+
+    @Override
+    protected void closeConnectionChannel(Transport transport, Transport.Connection connection) throws IOException {
+        final MockTcpTransport t = (MockTcpTransport) transport;
+        @SuppressWarnings("unchecked") final TcpTransport<MockTcpTransport.MockChannel>.NodeChannels channels =
+                (TcpTransport<MockTcpTransport.MockChannel>.NodeChannels) connection;
+        t.closeChannels(channels.getChannels().subList(0, randomIntBetween(1, channels.getChannels().size())), true, false);
+    }
+
 }

test/framework/src/test/java/org/elasticsearch/transport/nio/SimpleNioTransportTests.java

@@ -53,7 +53,7 @@
 public class SimpleNioTransportTests extends AbstractSimpleTransportTestCase {
 
     public static MockTransportService nioFromThreadPool(Settings settings, ThreadPool threadPool, final Version version,
-                                                           ClusterSettings clusterSettings, boolean doHandshake) {
+                                                         ClusterSettings clusterSettings, boolean doHandshake) {
         NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry(Collections.emptyList());
         NetworkService networkService = new NetworkService(Collections.emptyList());
         Transport transport = new NioTransport(settings, threadPool,
@@ -96,6 +96,13 @@ protected MockTransportService build(Settings settings, Version version, Cluster
         return transportService;
     }
 
+    @Override
+    protected void closeConnectionChannel(Transport transport, Transport.Connection connection) throws IOException {
+        final NioTransport t = (NioTransport) transport;
+        @SuppressWarnings("unchecked") TcpTransport<NioChannel>.NodeChannels channels = (TcpTransport<NioChannel>.NodeChannels) connection;
+        t.closeChannels(channels.getChannels().subList(0, randomIntBetween(1, channels.getChannels().size())), true, false);
+    }
+
     public void testConnectException() throws UnknownHostException {
         try {
             serviceA.connectToNode(new DiscoveryNode("C", new TransportAddress(InetAddress.getByName("localhost"), 9876),