Add TcpChannel to unify Transport implementations (#27132)

Right now our different transport implementations must duplicate
functionality in order to stay compliant with the requirements of
TcpTransport. They must all implement common logic to open channels,
close channels, keep track of channels for eventual shutdown, etc.

Additionally, there is a weird and complicated relationship between
Transport and TransportService. We eventually want to start merging
some of the functionality between these classes.

This commit starts moving towards a world where TransportService retains
all the application logic and channel state. Transport implementations
in this world will only be tasked with returning a channel when one is
requested, calling transport service when a channel is accepted from
a server, and starting / stopping itself.

Specifically this commit changes how channels are opened and closed. All
Transport implementations now return a channel type that must comply with
the new TcpChannel interface. This interface has the methods necessary
for TcpTransport to completely manage the lifecycle of a channel. This
includes setting the channel up, waiting for connection, adding close
listeners, and eventually closing.

Author: Tim-Brooks

core/src/main/java/org/elasticsearch/action/ActionListener.java

@@ -24,6 +24,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 
 /**
@@ -69,6 +70,42 @@ public void onFailure(Exception e) {
         };
     }
 
+    /**
+     * Creates a listener that listens for a response (or failure) and executes the
+     * corresponding runnable when the response (or failure) is received.
+     *
+     * @param runnable the runnable that will be called in event of success or failure
+     * @param <Response> the type of the response
+     * @return a listener that listens for responses and invokes the runnable when received
+     */
+    static <Response> ActionListener<Response> wrap(Runnable runnable) {
+        return wrap(r -> runnable.run(), e -> runnable.run());
+    }
+
+    /**
+     * Converts a listener to a {@link BiConsumer} for compatibility with the {@link java.util.concurrent.CompletableFuture}
+     * api.
+     *
+     * @param listener that will be wrapped
+     * @param <Response> the type of the response
+     * @return a bi consumer that will complete the wrapped listener
+     */
+    static <Response> BiConsumer<Response, Throwable> toBiConsumer(ActionListener<Response> listener) {
+        return (response, throwable) -> {
+            if (throwable == null) {
+                listener.onResponse(response);
+            } else {
+                if (throwable instanceof Exception) {
+                    listener.onFailure((Exception) throwable);
+                } else if (throwable instanceof Error) {
+                    throw (Error) throwable;
+                } else {
+                    throw new AssertionError("Should have been either Error or Exception", throwable);
+                }
+            }
+        };
+    }
+
     /**
      * Notifies every given listener with the response passed to {@link #onResponse(Object)}. If a listener itself throws an exception
      * the exception is forwarded to {@link #onFailure(Exception)}. If in turn {@link #onFailure(Exception)} fails all remaining

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

@@ -208,12 +208,12 @@ private ConnectionTypeHandle(int offset, int length, Set<TransportRequestOptions
          * Returns one of the channels out configured for this handle. The channel is selected in a round-robin
          * fashion.
          */
-        <T> T getChannel(T[] channels) {
+        <T> T getChannel(List<T> channels) {
             if (length == 0) {
                 throw new IllegalStateException("can't select channel size is 0 for types: " + types);
             }
-            assert channels.length >= offset + length : "illegal size: " + channels.length + " expected >= " + (offset + length);
-            return channels[offset + Math.floorMod(counter.incrementAndGet(), length)];
+            assert channels.size() >= offset + length : "illegal size: " + channels.size() + " expected >= " + (offset + length);
+            return channels.get(offset + Math.floorMod(counter.incrementAndGet(), length));
         }
 
         /**
@@ -223,5 +223,4 @@ Set<TransportRequestOptions.Type> getTypes() {
             return types;
         }
     }
-
 }

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

@@ -0,0 +1,169 @@
+/*
+ * 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.transport;
+
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.message.ParameterizedMessage;
+import org.elasticsearch.action.ActionFuture;
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.common.lease.Releasable;
+import org.elasticsearch.common.lease.Releasables;
+import org.elasticsearch.common.unit.TimeValue;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+
+/**
+ * This is a tcp channel representing a single channel connection to another node. It is the base channel
+ * abstraction used by the {@link TcpTransport} and {@link TransportService}. All tcp transport
+ * implementations must return channels that adhere to the required method contracts.
+ */
+public interface TcpChannel extends Releasable {
+
+    /**
+     * Closes the channel. This might be an asynchronous process. There is notguarantee that the channel
+     * will be closed when this method returns. Use the {@link #addCloseListener(ActionListener)} method
+     * to implement logic that depends on knowing when the channel is closed.
+     */
+    void close();
+
+    /**
+     * Adds a listener that will be executed when the channel is closed. If the channel is still open when
+     * this listener is added, the listener will be executed by the thread that eventually closes the
+     * channel. If the channel is already closed when the listener is added the listener will immediately be
+     * executed by the thread that is attempting to add the listener.
+     *
+     * @param listener to be executed
+     */
+    void addCloseListener(ActionListener<TcpChannel> listener);
+
+
+    /**
+     * This sets the low level socket option {@link java.net.StandardSocketOptions} SO_LINGER on a channel.
+     *
+     * @param value to set for SO_LINGER
+     * @throws IOException that can be throw by the low level socket implementation
+     */
+    void setSoLinger(int value) throws IOException;
+
+
+    /**
+     * Indicates whether a channel is currently open
+     *
+     * @return boolean indicating if channel is open
+     */
+    boolean isOpen();
+
+    /**
+     * Closes the channel.
+     *
+     * @param channel to close
+     * @param blocking indicates if we should block on channel close
+     */
+    static <C extends TcpChannel> void closeChannel(C channel, boolean blocking) {
+        closeChannels(Collections.singletonList(channel), blocking);
+    }
+
+    /**
+     * Closes the channels.
+     *
+     * @param channels to close
+     * @param blocking indicates if we should block on channel close
+     */
+    static <C extends TcpChannel> void closeChannels(List<C> channels, boolean blocking) {
+        if (blocking) {
+            ArrayList<ActionFuture<TcpChannel>> futures = new ArrayList<>(channels.size());
+            for (final C channel : channels) {
+                if (channel.isOpen()) {
+                    PlainActionFuture<TcpChannel> closeFuture = PlainActionFuture.newFuture();
+                    channel.addCloseListener(closeFuture);
+                    channel.close();
+                    futures.add(closeFuture);
+                }
+            }
+            blockOnFutures(futures);
+        } else {
+            Releasables.close(channels);
+        }
+    }
+
+    /**
+     * Awaits for all of the pending connections to complete. Will throw an exception if at least one of the
+     * connections fails.
+     *
+     * @param discoveryNode the node for the pending connections
+     * @param connectionFutures representing the pending connections
+     * @param connectTimeout to wait for a connection
+     * @param <C> the type of channel
+     * @throws ConnectTransportException if one of the connections fails
+     */
+    static <C extends TcpChannel> void awaitConnected(DiscoveryNode discoveryNode, List<ActionFuture<C>> connectionFutures,
+                                                      TimeValue connectTimeout) throws ConnectTransportException {
+        Exception connectionException = null;
+        boolean allConnected = true;
+
+        for (ActionFuture<C> connectionFuture : connectionFutures) {
+            try {
+                connectionFuture.get(connectTimeout.getMillis(), TimeUnit.MILLISECONDS);
+            } catch (TimeoutException e) {
+                allConnected = false;
+                break;
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new IllegalStateException(e);
+            } catch (ExecutionException e) {
+                allConnected = false;
+                connectionException = (Exception) e.getCause();
+                break;
+            }
+        }
+
+        if (allConnected == false) {
+            if (connectionException == null) {
+                throw new ConnectTransportException(discoveryNode, "connect_timeout[" + connectTimeout + "]");
+            } else {
+                throw new ConnectTransportException(discoveryNode, "connect_exception", connectionException);
+            }
+        }
+    }
+
+    static void blockOnFutures(List<ActionFuture<TcpChannel>> futures) {
+        for (ActionFuture<TcpChannel> future : futures) {
+            try {
+                future.get();
+            } catch (ExecutionException e) {
+                // Ignore as we are only interested in waiting for the close process to complete. Logging
+                // close exceptions happens elsewhere.
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new IllegalStateException("Future got interrupted", e);
+            }
+        }
+    }
+}