Make keepalive pings bidirectional and optimizable (elastic#35441)

This is related to elastic#34405 and a follow-up to elastic#34753. It makes a number
of changes to our current keepalive pings.

The ping interval configuration is moved to the ConnectionProfile.

The server channel now responds to pings. This makes the keepalive
pings bidirectional.

On the client-side, the pings can now be optimized away. What this
means is that if the channel has received a message or sent a message
since the last pinging round, the ping is not sent for this round.

Author: Tim-Brooks

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/Netty4TcpChannel.java

@@ -35,12 +35,15 @@
 public class Netty4TcpChannel implements TcpChannel {
 
     private final Channel channel;
+    private final boolean isServer;
     private final String profile;
     private final CompletableContext<Void> connectContext;
     private final CompletableContext<Void> closeContext = new CompletableContext<>();
+    private final ChannelStats stats = new ChannelStats();
 
-    Netty4TcpChannel(Channel channel, String profile, @Nullable ChannelFuture connectFuture) {
+    Netty4TcpChannel(Channel channel, boolean isServer, String profile, @Nullable ChannelFuture connectFuture) {
         this.channel = channel;
+        this.isServer = isServer;
         this.profile = profile;
         this.connectContext = new CompletableContext<>();
         this.channel.closeFuture().addListener(f -> {
@@ -77,6 +80,11 @@ public void close() {
         channel.close();
     }
 
+    @Override
+    public boolean isServerChannel() {
+        return isServer;
+    }
+
     @Override
     public String getProfile() {
         return profile;
@@ -92,6 +100,11 @@ public void addConnectListener(ActionListener<Void> listener) {
         connectContext.addListener(ActionListener.toBiConsumer(listener));
     }
 
+    @Override
+    public ChannelStats getChannelStats() {
+        return stats;
+    }
+
     @Override
     public boolean isOpen() {
         return channel.isOpen();

modules/transport-netty4/src/main/java/org/elasticsearch/transport/netty4/Netty4Transport.java

@@ -232,7 +232,7 @@ protected Netty4TcpChannel initiateChannel(DiscoveryNode node) throws IOExceptio
         }
         addClosedExceptionLogger(channel);
 
-        Netty4TcpChannel nettyChannel = new Netty4TcpChannel(channel, "default", connectFuture);
+        Netty4TcpChannel nettyChannel = new Netty4TcpChannel(channel, false, "default", connectFuture);
         channel.attr(CHANNEL_KEY).set(nettyChannel);
 
         return nettyChannel;
@@ -246,14 +246,6 @@ protected Netty4TcpServerChannel bind(String name, InetSocketAddress address) {
         return esChannel;
     }
 
-    long successfulPingCount() {
-        return successfulPings.count();
-    }
-
-    long failedPingCount() {
-        return failedPings.count();
-    }
-
     @Override
     @SuppressForbidden(reason = "debug")
     protected void stopInternal() {
@@ -297,8 +289,7 @@ protected ServerChannelInitializer(String name) {
         @Override
         protected void initChannel(Channel ch) throws Exception {
             addClosedExceptionLogger(ch);
-            Netty4TcpChannel nettyTcpChannel = new Netty4TcpChannel(ch, name, ch.newSucceededFuture());
-
+            Netty4TcpChannel nettyTcpChannel = new Netty4TcpChannel(ch, true, name, ch.newSucceededFuture());
             ch.attr(CHANNEL_KEY).set(nettyTcpChannel);
             serverAcceptedChannel(nettyTcpChannel);
             ch.pipeline().addLast("logging", new ESLoggingHandler());

modules/transport-netty4/src/test/java/org/elasticsearch/transport/netty4/Netty4ScheduledPingTests.java

@@ -0,0 +1,29 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.common;
+
+import org.elasticsearch.action.ActionListener;
+
+/**
+ * A {@link java.util.function.BiFunction}-like interface designed to be used with asynchronous executions.
+ */
+public interface AsyncBiFunction<T,U,C> {
+
+    void apply(T t, U u, ActionListener<C> listener);
+}

server/src/main/java/org/elasticsearch/common/AsyncBiFunction.java

@@ -27,10 +27,7 @@
 import org.elasticsearch.common.component.Lifecycle;
 import org.elasticsearch.common.lease.Releasable;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.unit.TimeValue;
-import org.elasticsearch.common.util.concurrent.AbstractLifecycleRunnable;
 import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
-import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
 import org.elasticsearch.common.util.concurrent.KeyedLock;
 import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.threadpool.ThreadPool;
@@ -53,32 +50,28 @@
  * the connection when the connection manager is closed.
  */
 public class ConnectionManager implements Closeable {
+
     private static final Logger logger = LogManager.getLogger(ConnectionManager.class);
 
     private final ConcurrentMap<DiscoveryNode, Transport.Connection> connectedNodes = ConcurrentCollections.newConcurrentMap();
     private final KeyedLock<String> connectionLock = new KeyedLock<>();
     private final Transport transport;
     private final ThreadPool threadPool;
-    private final TimeValue pingSchedule;
     private final ConnectionProfile defaultProfile;
     private final Lifecycle lifecycle = new Lifecycle();
     private final AtomicBoolean closed = new AtomicBoolean(false);
     private final ReadWriteLock closeLock = new ReentrantReadWriteLock();
     private final DelegatingNodeConnectionListener connectionListener = new DelegatingNodeConnectionListener();
 
     public ConnectionManager(Settings settings, Transport transport, ThreadPool threadPool) {
-        this(settings, transport, threadPool, TcpTransport.PING_SCHEDULE.get(settings));
+        this(ConnectionProfile.buildDefaultConnectionProfile(settings), transport, threadPool);
     }
 
-    public ConnectionManager(Settings settings, Transport transport, ThreadPool threadPool, TimeValue pingSchedule) {
+    public ConnectionManager(ConnectionProfile connectionProfile, Transport transport, ThreadPool threadPool) {
         this.transport = transport;
         this.threadPool = threadPool;
-        this.pingSchedule = pingSchedule;
-        this.defaultProfile = ConnectionProfile.buildDefaultConnectionProfile(settings);
+        this.defaultProfile = connectionProfile;
         this.lifecycle.moveToStarted();
-        if (pingSchedule.millis() > 0) {
-            threadPool.schedule(pingSchedule, ThreadPool.Names.GENERIC, new ScheduledPing());
-        }
     }
 
     public void addListener(TransportConnectionListener listener) {
@@ -251,47 +244,8 @@ private void ensureOpen() {
         }
     }
 
-    TimeValue getPingSchedule() {
-        return pingSchedule;
-    }
-
-    private class ScheduledPing extends AbstractLifecycleRunnable {
-
-        private ScheduledPing() {
-            super(lifecycle, logger);
-        }
-
-        @Override
-        protected void doRunInLifecycle() {
-            for (Map.Entry<DiscoveryNode, Transport.Connection> entry : connectedNodes.entrySet()) {
-                Transport.Connection connection = entry.getValue();
-                if (connection.sendPing() == false) {
-                    logger.warn("attempted to send ping to connection without support for pings [{}]", connection);
-                }
-            }
-        }
-
-        @Override
-        protected void onAfterInLifecycle() {
-            try {
-                threadPool.schedule(pingSchedule, ThreadPool.Names.GENERIC, this);
-            } catch (EsRejectedExecutionException ex) {
-                if (ex.isExecutorShutdown()) {
-                    logger.debug("couldn't schedule new ping execution, executor is shutting down", ex);
-                } else {
-                    throw ex;
-                }
-            }
-        }
-
-        @Override
-        public void onFailure(Exception e) {
-            if (lifecycle.stoppedOrClosed()) {
-                logger.trace("failed to send ping transport message", e);
-            } else {
-                logger.warn("failed to send ping transport message", e);
-            }
-        }
+    ConnectionProfile getConnectionProfile() {
+        return defaultProfile;
     }
 
     private static final class DelegatingNodeConnectionListener implements TransportConnectionListener {