Remove some overhead from TransportService message handling

Avoiding some indirection, volatile-reads and moving the listener
functionality that needlessly kept iterating an empty CoW list (creating
iterator instances, volatile reads, more code) in an effort to improve
the low IPC on transport threads.

Author: original-brownbear

server/src/internalClusterTest/java/org/elasticsearch/snapshots/DedicatedClusterSnapshotRestoreIT.java

@@ -66,7 +66,6 @@
 import org.elasticsearch.transport.TransportMessageListener;
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestOptions;
-import org.elasticsearch.transport.TransportService;
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
@@ -1052,8 +1051,7 @@ public void testAbortWaitsOnDataNode() throws Exception {
 
         final AtomicBoolean blocked = new AtomicBoolean(true);
 
-        final TransportService transportService = internalCluster().getInstance(TransportService.class, otherDataNode);
-        transportService.addMessageListener(new TransportMessageListener() {
+        MockTransportService.getInstance(otherDataNode).addMessageListener(new TransportMessageListener() {
             @Override
             public void onRequestSent(
                 DiscoveryNode node,

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

@@ -60,11 +60,9 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
@@ -103,8 +101,7 @@ public class TransportService extends AbstractLifecycleComponent
         Setting.Property.Deprecated
     );
 
-    private final AtomicBoolean handleIncomingRequests = new AtomicBoolean();
-    private final DelegatingTransportMessageListener messageListener = new DelegatingTransportMessageListener();
+    private volatile boolean handleIncomingRequests;
     protected final Transport transport;
     protected final ConnectionManager connectionManager;
     protected final ThreadPool threadPool;
@@ -134,7 +131,7 @@ protected boolean removeEldestEntry(Map.Entry<Long, TimeoutInfoHolder> eldest) {
 
     // tracer log
 
-    private final Logger tracerLog;
+    private static final Logger tracerLog = Loggers.getLogger(logger, ".tracer");
     private final Tracer tracer;
 
     volatile String[] tracerLogInclude;
@@ -291,7 +288,6 @@ public TransportService(
         this.clusterName = ClusterName.CLUSTER_NAME_SETTING.get(settings);
         setTracerLogInclude(TransportSettings.TRACE_LOG_INCLUDE_SETTING.get(settings));
         setTracerLogExclude(TransportSettings.TRACE_LOG_EXCLUDE_SETTING.get(settings));
-        tracerLog = Loggers.getLogger(logger, ".tracer");
         this.taskManager = taskManger;
         this.interceptor = transportInterceptor;
         this.asyncSender = interceptor.interceptSender(this::sendRequestInternal);
@@ -432,8 +428,8 @@ protected void doClose() throws IOException {
      * reject any incoming requests, including handshakes, by closing the connection.
      */
     public final void acceptIncomingRequests() {
-        final boolean startedWithThisCall = handleIncomingRequests.compareAndSet(false, true);
-        assert startedWithThisCall : "transport service was already accepting incoming requests";
+        assert handleIncomingRequests == false : "transport service was already accepting incoming requests";
+        handleIncomingRequests = true;
         logger.debug("now accepting incoming requests");
     }
 
@@ -750,14 +746,6 @@ public void disconnectFromNode(DiscoveryNode node) {
         connectionManager.disconnectFromNode(node);
     }
 
-    public void addMessageListener(TransportMessageListener listener) {
-        messageListener.listeners.add(listener);
-    }
-
-    public void removeMessageListener(TransportMessageListener listener) {
-        messageListener.listeners.remove(listener);
-    }
-
     public void addConnectionListener(TransportConnectionListener listener) {
         connectionManager.addListener(listener);
     }
@@ -1265,13 +1253,12 @@ public <Request extends TransportRequest> void registerRequestHandler(
      */
     @Override
     public void onRequestReceived(long requestId, String action) {
-        if (handleIncomingRequests.get() == false) {
+        if (handleIncomingRequests == false) {
             throw new TransportNotReadyException();
         }
         if (tracerLog.isTraceEnabled() && shouldTraceAction(action)) {
             tracerLog.trace("[{}][{}] received request", requestId, action);
         }
-        messageListener.onRequestReceived(requestId, action);
     }
 
     /** called by the {@link Transport} implementation once a request has been sent */
@@ -1286,7 +1273,6 @@ public void onRequestSent(
         if (tracerLog.isTraceEnabled() && shouldTraceAction(action)) {
             tracerLog.trace("[{}][{}] sent to [{}] (timeout: [{}])", requestId, action, node, options.timeout());
         }
-        messageListener.onRequestSent(node, requestId, action, request, options);
     }
 
     @Override
@@ -1297,7 +1283,6 @@ public void onResponseReceived(long requestId, Transport.ResponseContext holder)
         } else if (tracerLog.isTraceEnabled() && shouldTraceAction(holder.action())) {
             tracerLog.trace("[{}][{}] received response from [{}]", requestId, holder.action(), holder.connection().getNode());
         }
-        messageListener.onResponseReceived(requestId, holder);
     }
 
     /** called by the {@link Transport} implementation once a response was sent to calling node */
@@ -1306,7 +1291,6 @@ public void onResponseSent(long requestId, String action, TransportResponse resp
         if (tracerLog.isTraceEnabled() && shouldTraceAction(action)) {
             tracerLog.trace("[{}][{}] sent response", requestId, action);
         }
-        messageListener.onResponseSent(requestId, action, response);
     }
 
     /** called by the {@link Transport} implementation after an exception was sent as a response to an incoming request */
@@ -1315,7 +1299,6 @@ public void onResponseSent(long requestId, String action, Exception e) {
         if (tracerLog.isTraceEnabled() && shouldTraceAction(action)) {
             tracerLog.trace(() -> format("[%s][%s] sent error response", requestId, action), e);
         }
-        messageListener.onResponseSent(requestId, action, e);
     }
 
     public RequestHandlerRegistry<? extends TransportRequest> getRequestHandler(String action) {
@@ -1453,6 +1436,7 @@ public void run() {
         public void cancel() {
             assert responseHandlers.contains(requestId) == false
                 : "cancel must be called after the requestId [" + requestId + "] has been removed from clientHandlers";
+            var cancellable = this.cancellable;
             if (cancellable != null) {
                 cancellable.cancel();
             }
@@ -1492,6 +1476,7 @@ public T read(StreamInput in) throws IOException {
 
         @Override
         public void handleResponse(T response) {
+            var handler = this.handler;
             if (handler != null) {
                 handler.cancel();
             }
@@ -1502,6 +1487,7 @@ public void handleResponse(T response) {
 
         @Override
         public void handleException(TransportException exp) {
+            var handler = this.handler;
             if (handler != null) {
                 handler.cancel();
             }
@@ -1666,53 +1652,6 @@ private boolean isLocalNode(DiscoveryNode discoveryNode) {
         return discoveryNode.equals(localNode);
     }
 
-    private static final class DelegatingTransportMessageListener implements TransportMessageListener {
-
-        private final List<TransportMessageListener> listeners = new CopyOnWriteArrayList<>();
-
-        @Override
-        public void onRequestReceived(long requestId, String action) {
-            for (TransportMessageListener listener : listeners) {
-                listener.onRequestReceived(requestId, action);
-            }
-        }
-
-        @Override
-        public void onResponseSent(long requestId, String action, TransportResponse response) {
-            for (TransportMessageListener listener : listeners) {
-                listener.onResponseSent(requestId, action, response);
-            }
-        }
-
-        @Override
-        public void onResponseSent(long requestId, String action, Exception error) {
-            for (TransportMessageListener listener : listeners) {
-                listener.onResponseSent(requestId, action, error);
-            }
-        }
-
-        @Override
-        public void onRequestSent(
-            DiscoveryNode node,
-            long requestId,
-            String action,
-            TransportRequest request,
-            TransportRequestOptions finalOptions
-        ) {
-            for (TransportMessageListener listener : listeners) {
-                listener.onRequestSent(node, requestId, action, request, finalOptions);
-            }
-        }
-
-        @Override
-        @SuppressWarnings("rawtypes")
-        public void onResponseReceived(long requestId, Transport.ResponseContext holder) {
-            for (TransportMessageListener listener : listeners) {
-                listener.onResponseReceived(requestId, holder);
-            }
-        }
-    }
-
     private static class PendingDirectHandlers extends AbstractRefCounted {
 
         // To handle a response we (i) remove the handler from responseHandlers and then (ii) enqueue an action to complete the handler on

test/framework/src/main/java/org/elasticsearch/search/ErrorTraceHelper.java

@@ -11,6 +11,7 @@
 
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.test.InternalTestCluster;
+import org.elasticsearch.test.transport.MockTransportService;
 import org.elasticsearch.transport.TransportMessageListener;
 import org.elasticsearch.transport.TransportService;
 
@@ -26,16 +27,20 @@ public enum ErrorTraceHelper {
 
     public static BooleanSupplier setupErrorTraceListener(InternalTestCluster internalCluster) {
         final AtomicBoolean transportMessageHasStackTrace = new AtomicBoolean(false);
-        internalCluster.getDataNodeInstances(TransportService.class).forEach(ts -> ts.addMessageListener(new TransportMessageListener() {
-            @Override
-            public void onResponseSent(long requestId, String action, Exception error) {
-                TransportMessageListener.super.onResponseSent(requestId, action, error);
-                if (action.startsWith("indices:data/read/search")) {
-                    Optional<Throwable> throwable = ExceptionsHelper.unwrapCausesAndSuppressed(error, t -> t.getStackTrace().length > 0);
-                    transportMessageHasStackTrace.set(throwable.isPresent());
+        internalCluster.getDataNodeInstances(TransportService.class)
+            .forEach(ts -> ((MockTransportService) ts).addMessageListener(new TransportMessageListener() {
+                @Override
+                public void onResponseSent(long requestId, String action, Exception error) {
+                    TransportMessageListener.super.onResponseSent(requestId, action, error);
+                    if (action.startsWith("indices:data/read/search")) {
+                        Optional<Throwable> throwable = ExceptionsHelper.unwrapCausesAndSuppressed(
+                            error,
+                            t -> t.getStackTrace().length > 0
+                        );
+                        transportMessageHasStackTrace.set(throwable.isPresent());
+                    }
                 }
-            }
-        }));
+            }));
         return transportMessageHasStackTrace::get;
     }
 }

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

@@ -57,8 +57,10 @@
 import org.elasticsearch.transport.TcpTransport;
 import org.elasticsearch.transport.Transport;
 import org.elasticsearch.transport.TransportInterceptor;
+import org.elasticsearch.transport.TransportMessageListener;
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestOptions;
+import org.elasticsearch.transport.TransportResponse;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.transport.TransportSettings;
 import org.elasticsearch.transport.netty4.Netty4Transport;
@@ -106,6 +108,8 @@ public class MockTransportService extends TransportService {
     private final List<Runnable> onStopListeners = new CopyOnWriteArrayList<>();
     private final AtomicReference<Consumer<Transport.Connection>> onConnectionClosedCallback = new AtomicReference<>();
 
+    private final DelegatingTransportMessageListener messageListener = new DelegatingTransportMessageListener();
+
     public static class TestPlugin extends Plugin {
         @Override
         public List<Setting<?>> getSettings() {
@@ -814,4 +818,96 @@ protected void doClose() throws IOException {
             assertTrue(ThreadPool.terminate(testExecutor, 10, TimeUnit.SECONDS));
         }
     }
+
+    @Override
+    public void onRequestReceived(long requestId, String action) {
+        super.onRequestReceived(requestId, action);
+        messageListener.onRequestReceived(requestId, action);
+    }
+
+    @Override
+    public void onRequestSent(
+        DiscoveryNode node,
+        long requestId,
+        String action,
+        TransportRequest request,
+        TransportRequestOptions options
+    ) {
+        super.onRequestSent(node, requestId, action, request, options);
+        messageListener.onRequestSent(node, requestId, action, request, options);
+    }
+
+    @Override
+    @SuppressWarnings("rawtypes")
+    public void onResponseReceived(long requestId, Transport.ResponseContext holder) {
+        super.onResponseReceived(requestId, holder);
+        messageListener.onResponseReceived(requestId, holder);
+    }
+
+    @Override
+    public void onResponseSent(long requestId, String action, TransportResponse response) {
+        super.onResponseSent(requestId, action, response);
+        messageListener.onResponseSent(requestId, action, response);
+    }
+
+    @Override
+    public void onResponseSent(long requestId, String action, Exception e) {
+        super.onResponseSent(requestId, action, e);
+        messageListener.onResponseSent(requestId, action, e);
+    }
+
+    public void addMessageListener(TransportMessageListener listener) {
+        messageListener.listeners.add(listener);
+    }
+
+    public void removeMessageListener(TransportMessageListener listener) {
+        messageListener.listeners.remove(listener);
+    }
+
+    private static final class DelegatingTransportMessageListener implements TransportMessageListener {
+
+        private final List<TransportMessageListener> listeners = new CopyOnWriteArrayList<>();
+
+        @Override
+        public void onRequestReceived(long requestId, String action) {
+            for (TransportMessageListener listener : listeners) {
+                listener.onRequestReceived(requestId, action);
+            }
+        }
+
+        @Override
+        public void onResponseSent(long requestId, String action, TransportResponse response) {
+            for (TransportMessageListener listener : listeners) {
+                listener.onResponseSent(requestId, action, response);
+            }
+        }
+
+        @Override
+        public void onResponseSent(long requestId, String action, Exception error) {
+            for (TransportMessageListener listener : listeners) {
+                listener.onResponseSent(requestId, action, error);
+            }
+        }
+
+        @Override
+        public void onRequestSent(
+            DiscoveryNode node,
+            long requestId,
+            String action,
+            TransportRequest request,
+            TransportRequestOptions finalOptions
+        ) {
+            for (TransportMessageListener listener : listeners) {
+                listener.onRequestSent(node, requestId, action, request, finalOptions);
+            }
+        }
+
+        @Override
+        @SuppressWarnings("rawtypes")
+        public void onResponseReceived(long requestId, Transport.ResponseContext holder) {
+            for (TransportMessageListener listener : listeners) {
+                listener.onResponseReceived(requestId, holder);
+            }
+        }
+    }
 }