elastic · elasticsearchmachine · Apr 7, 2025 · Apr 7, 2025 · Apr 7, 2025 · Apr 7, 2025
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/common/network/ThreadWatchdogIT.java b/server/src/internalClusterTest/java/org/elasticsearch/common/network/ThreadWatchdogIT.java
@@ -11,6 +11,7 @@
 
 import org.apache.logging.log4j.Level;
 import org.elasticsearch.action.ActionListenerResponseHandler;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.client.Request;
 import org.elasticsearch.client.internal.node.NodeClient;
@@ -137,7 +138,7 @@ public void testThreadWatchdogTransportLogging() {
             EmptyRequest::new,
             (request, channel, task) -> {
                 blockAndWaitForWatchdogLogs();
-                channel.sendResponse(TransportResponse.Empty.INSTANCE);
+                channel.sendResponse(ActionResponse.Empty.INSTANCE);
             }
         );
 
@@ -149,7 +150,7 @@ public void testThreadWatchdogTransportLogging() {
                     new EmptyRequest(),
                     new ActionListenerResponseHandler<TransportResponse>(
                         l,
-                        in -> TransportResponse.Empty.INSTANCE,
+                        in -> ActionResponse.Empty.INSTANCE,
                         EsExecutors.DIRECT_EXECUTOR_SERVICE
                     )
                 )

diff --git a/server/src/main/java/org/elasticsearch/action/search/SearchTransportService.java b/server/src/main/java/org/elasticsearch/action/search/SearchTransportService.java
@@ -13,6 +13,7 @@
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.ActionListenerResponseHandler;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.OriginalIndices;
 import org.elasticsearch.action.admin.cluster.node.tasks.cancel.CancelTasksRequest;
 import org.elasticsearch.action.admin.cluster.node.tasks.get.TransportGetTaskAction;
@@ -161,7 +162,7 @@ public void sendClearAllScrollContexts(Transport.Connection connection, final Ac
             CLEAR_SCROLL_CONTEXTS_ACTION_NAME,
             new ClearScrollContextsRequest(),
             TransportRequestOptions.EMPTY,
-            new ActionListenerResponseHandler<>(listener, in -> TransportResponse.Empty.INSTANCE, TransportResponseHandler.TRANSPORT_WORKER)
+            new ActionListenerResponseHandler<>(listener, in -> ActionResponse.Empty.INSTANCE, TransportResponseHandler.TRANSPORT_WORKER)
         );
     }
 
@@ -418,14 +419,14 @@ public static void registerRequestHandler(TransportService transportService, Sea
             ClearScrollContextsRequest::new,
             (request, channel, task) -> {
                 searchService.freeAllScrollContexts();
-                channel.sendResponse(TransportResponse.Empty.INSTANCE);
+                channel.sendResponse(ActionResponse.Empty.INSTANCE);
             }
         );
         TransportActionProxy.registerProxyAction(
             transportService,
             CLEAR_SCROLL_CONTEXTS_ACTION_NAME,
             false,
-            (in) -> TransportResponse.Empty.INSTANCE
+            (in) -> ActionResponse.Empty.INSTANCE
         );
 
         transportService.registerRequestHandler(

diff --git a/server/src/main/java/org/elasticsearch/cluster/action/shard/ShardStateAction.java b/server/src/main/java/org/elasticsearch/cluster/action/shard/ShardStateAction.java
@@ -16,6 +16,7 @@
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ResultDeduplicator;
 import org.elasticsearch.action.support.ChannelActionListener;
 import org.elasticsearch.cluster.ClusterState;
@@ -57,7 +58,6 @@
 import org.elasticsearch.transport.TransportChannel;
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestHandler;
-import org.elasticsearch.transport.TransportResponse;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 
@@ -291,7 +291,7 @@ public void messageReceived(FailedShardEntry request, TransportChannel channel,
             logger.debug(() -> format("%s received shard failed for [%s]", request.getShardId(), request), request.failure);
             taskQueue.submitTask(
                 "shard-failed " + request.toStringNoFailureStackTrace(),
-                new FailedShardUpdateTask(request, new ChannelActionListener<>(channel).map(ignored -> TransportResponse.Empty.INSTANCE)),
+                new FailedShardUpdateTask(request, new ChannelActionListener<>(channel).map(ignored -> ActionResponse.Empty.INSTANCE)),
                 null
             );
         }
@@ -602,7 +602,7 @@ public void messageReceived(StartedShardEntry request, TransportChannel channel,
             logger.debug("{} received shard started for [{}]", request.shardId, request);
             taskQueue.submitTask(
                 "shard-started " + request,
-                new StartedShardUpdateTask(request, new ChannelActionListener<>(channel).map(ignored -> TransportResponse.Empty.INSTANCE)),
+                new StartedShardUpdateTask(request, new ChannelActionListener<>(channel).map(ignored -> ActionResponse.Empty.INSTANCE)),
                 null
             );
         }

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java b/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
@@ -13,6 +13,7 @@
 import org.apache.logging.log4j.Logger;
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse.Empty;
 import org.elasticsearch.action.support.ChannelActionListener;
 import org.elasticsearch.action.support.RefCountingListener;
 import org.elasticsearch.action.support.SubscribableListener;
@@ -77,7 +78,6 @@
 import org.elasticsearch.threadpool.ThreadPool.Names;
 import org.elasticsearch.transport.NodeDisconnectedException;
 import org.elasticsearch.transport.TransportRequestOptions;
-import org.elasticsearch.transport.TransportResponse.Empty;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.transport.Transports;

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/FollowersChecker.java b/server/src/main/java/org/elasticsearch/cluster/coordination/FollowersChecker.java
@@ -12,6 +12,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse.Empty;
 import org.elasticsearch.action.ActionRunnable;
 import org.elasticsearch.action.support.ChannelActionListener;
 import org.elasticsearch.cluster.coordination.Coordinator.Mode;
@@ -37,7 +38,6 @@
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestOptions;
 import org.elasticsearch.transport.TransportRequestOptions.Type;
-import org.elasticsearch.transport.TransportResponse.Empty;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/JoinHelper.java b/server/src/main/java/org/elasticsearch/cluster/coordination/JoinHelper.java
@@ -13,6 +13,7 @@
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse.Empty;
 import org.elasticsearch.action.support.ChannelActionListener;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.coordination.Coordinator.Mode;
@@ -45,7 +46,6 @@
 import org.elasticsearch.transport.TransportException;
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestOptions;
-import org.elasticsearch.transport.TransportResponse.Empty;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/JoinValidationService.java b/server/src/main/java/org/elasticsearch/cluster/coordination/JoinValidationService.java
@@ -14,6 +14,7 @@
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionRunnable;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.Metadata;
@@ -39,7 +40,6 @@
 import org.elasticsearch.transport.NodeNotConnectedException;
 import org.elasticsearch.transport.Transport;
 import org.elasticsearch.transport.TransportRequestOptions;
-import org.elasticsearch.transport.TransportResponse;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 
@@ -143,7 +143,7 @@ public JoinValidationService(
                     );
                 }
                 joinValidators.forEach(joinValidator -> joinValidator.accept(transportService.getLocalNode(), remoteState));
-                channel.sendResponse(TransportResponse.Empty.INSTANCE);
+                channel.sendResponse(ActionResponse.Empty.INSTANCE);
             }
         );
     }
@@ -343,7 +343,7 @@ protected void doRun() {
                 REQUEST_OPTIONS,
                 new CleanableResponseHandler<>(
                     listener.map(ignored -> null),
-                    in -> TransportResponse.Empty.INSTANCE,
+                    in -> ActionResponse.Empty.INSTANCE,
                     responseExecutor,
                     bytes::decRef
                 )

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/LeaderChecker.java b/server/src/main/java/org/elasticsearch/cluster/coordination/LeaderChecker.java
@@ -12,6 +12,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ExceptionsHelper;
+import org.elasticsearch.action.ActionResponse.Empty;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -36,7 +37,6 @@
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestOptions;
 import org.elasticsearch.transport.TransportRequestOptions.Type;
-import org.elasticsearch.transport.TransportResponse.Empty;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 

diff --git a/server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java b/server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java
@@ -565,7 +565,7 @@ public void messageReceived(final RecoveryHandoffPrimaryContextRequest request,
                     .handoffPrimaryContext(
                         request.primaryContext(),
                         ActionListener.runBefore(
-                            new ChannelActionListener<>(channel).map(v -> TransportResponse.Empty.INSTANCE),
+                            new ChannelActionListener<>(channel).map(v -> ActionResponse.Empty.INSTANCE),
                             recoveryRef::close
                         )
                     );
@@ -688,7 +688,7 @@ public final void messageReceived(final T request, TransportChannel channel, Tas
         }
 
         protected CheckedFunction<Void, TransportResponse, Exception> responseMapping(RecoveryTarget recoveryTarget) {
-            return v -> TransportResponse.Empty.INSTANCE;
+            return v -> ActionResponse.Empty.INSTANCE;
         }
 
         protected abstract void handleRequest(T request, RecoveryTarget target, ActionListener<Void> listener) throws IOException;

diff --git a/server/src/main/java/org/elasticsearch/indices/recovery/RemoteRecoveryTargetHandler.java b/server/src/main/java/org/elasticsearch/indices/recovery/RemoteRecoveryTargetHandler.java
@@ -17,6 +17,7 @@
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.ActionListenerResponseHandler;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionRunnable;
 import org.elasticsearch.action.support.RetryableAction;
 import org.elasticsearch.cluster.node.DiscoveryNode;
@@ -116,7 +117,7 @@ public void prepareForTranslogOperations(int totalTranslogOps, ActionListener<Vo
             shardId,
             totalTranslogOps
         );
-        final Writeable.Reader<TransportResponse.Empty> reader = in -> TransportResponse.Empty.INSTANCE;
+        final Writeable.Reader<ActionResponse.Empty> reader = in -> ActionResponse.Empty.INSTANCE;
         executeRetryableAction(action, request, standardTimeoutRequestOptions, listener.map(r -> null), reader);
     }
 
@@ -131,7 +132,7 @@ public void finalizeRecovery(final long globalCheckpoint, final long trimAboveSe
             globalCheckpoint,
             trimAboveSeqNo
         );
-        final Writeable.Reader<TransportResponse.Empty> reader = in -> TransportResponse.Empty.INSTANCE;
+        final Writeable.Reader<ActionResponse.Empty> reader = in -> ActionResponse.Empty.INSTANCE;
         executeRetryableAction(
             action,
             request,
@@ -148,7 +149,7 @@ public void handoffPrimaryContext(final ReplicationTracker.PrimaryContext primar
             PeerRecoveryTargetService.Actions.HANDOFF_PRIMARY_CONTEXT,
             new RecoveryHandoffPrimaryContextRequest(recoveryId, shardId, primaryContext),
             standardTimeoutRequestOptions,
-            new ActionListenerResponseHandler<>(listener.map(r -> null), in -> TransportResponse.Empty.INSTANCE, threadPool.generic())
+            new ActionListenerResponseHandler<>(listener.map(r -> null), in -> ActionResponse.Empty.INSTANCE, threadPool.generic())
         );
     }
 
@@ -200,7 +201,7 @@ public void receiveFileInfo(
             phase1ExistingFileSizes,
             totalTranslogOps
         );
-        final Writeable.Reader<TransportResponse.Empty> reader = in -> TransportResponse.Empty.INSTANCE;
+        final Writeable.Reader<ActionResponse.Empty> reader = in -> ActionResponse.Empty.INSTANCE;
         executeRetryableAction(action, request, standardTimeoutRequestOptions, listener.map(r -> null), reader);
     }
 
@@ -221,8 +222,8 @@ public void cleanFiles(
             totalTranslogOps,
             globalCheckpoint
         );
-        final Writeable.Reader<TransportResponse.Empty> reader = in -> TransportResponse.Empty.INSTANCE;
-        final ActionListener<TransportResponse.Empty> responseListener = listener.map(r -> null);
+        final Writeable.Reader<ActionResponse.Empty> reader = in -> ActionResponse.Empty.INSTANCE;
+        final ActionListener<ActionResponse.Empty> responseListener = listener.map(r -> null);
         executeRetryableAction(action, request, TransportRequestOptions.EMPTY, responseListener, reader);
     }
 
@@ -243,8 +244,8 @@ public void restoreFileFromSnapshot(
             indexId,
             snapshotFile
         );
-        final Writeable.Reader<TransportResponse.Empty> reader = in -> TransportResponse.Empty.INSTANCE;
-        final ActionListener<TransportResponse.Empty> responseListener = listener.map(r -> null);
+        final Writeable.Reader<ActionResponse.Empty> reader = in -> ActionResponse.Empty.INSTANCE;
+        final ActionListener<ActionResponse.Empty> responseListener = listener.map(r -> null);
         executeRetryableAction(action, request, TransportRequestOptions.EMPTY, responseListener, reader);
     }
 
@@ -303,8 +304,8 @@ public void writeFileChunk(
         threadPool.generic()
             .execute(
                 ActionRunnable.wrap(
-                    ActionListener.<TransportResponse.Empty>runBefore(listener.map(r -> null), request::decRef),
-                    l -> executeRetryableAction(action, request, fileChunkRequestOptions, l, in -> TransportResponse.Empty.INSTANCE)
+                    ActionListener.<ActionResponse.Empty>runBefore(listener.map(r -> null), request::decRef),
+                    l -> executeRetryableAction(action, request, fileChunkRequestOptions, l, in -> ActionResponse.Empty.INSTANCE)
                 )
             );
     }

diff --git a/server/src/main/java/org/elasticsearch/tasks/TaskCancellationService.java b/server/src/main/java/org/elasticsearch/tasks/TaskCancellationService.java
@@ -16,6 +16,7 @@
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ResultDeduplicator;
 import org.elasticsearch.action.support.ChannelActionListener;
 import org.elasticsearch.action.support.CountDownActionListener;
@@ -34,7 +35,6 @@
 import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.transport.TransportRequestHandler;
 import org.elasticsearch.transport.TransportRequestOptions;
-import org.elasticsearch.transport.TransportResponse;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 
@@ -361,7 +361,7 @@ public void messageReceived(final BanParentTaskRequest request, final TransportC
                 final List<CancellableTask> childTasks = taskManager.setBan(request.parentTaskId, request.reason, channel);
                 final GroupedActionListener<Void> listener = new GroupedActionListener<>(
                     childTasks.size() + 1,
-                    new ChannelActionListener<>(channel).map(r -> TransportResponse.Empty.INSTANCE)
+                    new ChannelActionListener<>(channel).map(r -> ActionResponse.Empty.INSTANCE)
                 );
                 for (CancellableTask childTask : childTasks) {
                     cancelTaskAndDescendants(childTask, request.reason, request.waitForCompletion, listener);
@@ -370,7 +370,7 @@ public void messageReceived(final BanParentTaskRequest request, final TransportC
             } else {
                 logger.debug("Removing ban for the parent [{}] on the node [{}]", request.parentTaskId, localNodeId());
                 taskManager.removeBan(request.parentTaskId);
-                channel.sendResponse(TransportResponse.Empty.INSTANCE);
+                channel.sendResponse(ActionResponse.Empty.INSTANCE);
             }
         }
     }
@@ -411,7 +411,7 @@ private class CancelChildRequestHandler implements TransportRequestHandler<Cance
         @Override
         public void messageReceived(final CancelChildRequest request, final TransportChannel channel, Task task) throws Exception {
             taskManager.cancelChildLocal(request.parentTaskId, request.childRequestId, request.reason);
-            channel.sendResponse(TransportResponse.Empty.INSTANCE);
+            channel.sendResponse(ActionResponse.Empty.INSTANCE);
         }
     }
 

diff --git a/server/src/main/java/org/elasticsearch/transport/TransportResponse.java b/server/src/main/java/org/elasticsearch/transport/TransportResponse.java
@@ -9,28 +9,9 @@
 
 package org.elasticsearch.transport;
 
-import org.elasticsearch.common.io.stream.StreamOutput;
-
-import java.io.IOException;
-
 public abstract class TransportResponse extends TransportMessage {
-
     /**
      * Constructs a new empty transport response
      */
-    public TransportResponse() {}
-
-    public static class Empty extends TransportResponse {
-        public static final Empty INSTANCE = new Empty();
-
-        private Empty() {/* singleton */}
-
-        @Override
-        public String toString() {
-            return "Empty{}";
-        }
-
-        @Override
-        public void writeTo(StreamOutput out) throws IOException {}
-    }
+    protected TransportResponse() {}
 }
diff --git a/server/src/main/java/org/elasticsearch/transport/TransportResponseHandler.java b/server/src/main/java/org/elasticsearch/transport/TransportResponseHandler.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.transport;
 
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
@@ -31,16 +32,16 @@ public interface TransportResponseHandler<T extends TransportResponse> extends W
     void handleException(TransportException exp);
 
     /**
-     * Implementation of {@link TransportResponseHandler} that handles the empty response {@link TransportResponse.Empty}.
+     * Implementation of {@link TransportResponseHandler} that handles the empty response {@link ActionResponse.Empty}.
      */
-    abstract class Empty implements TransportResponseHandler<TransportResponse.Empty> {
+    abstract class Empty implements TransportResponseHandler<ActionResponse.Empty> {
         @Override
-        public final TransportResponse.Empty read(StreamInput in) {
-            return TransportResponse.Empty.INSTANCE;
+        public final ActionResponse.Empty read(StreamInput in) {
+            return ActionResponse.Empty.INSTANCE;
         }
 
         @Override
-        public final void handleResponse(TransportResponse.Empty ignored) {
+        public final void handleResponse(ActionResponse.Empty ignored) {
             handleResponse();
         }