Send clear session as routable remote request (#36805)

This commit adds a RemoteClusterAwareRequest interface that allows a
request to specify which remote node it should be routed to. The remote
cluster aware client will attempt to route the request directly to this
node. Otherwise it will send it as a proxy action to eventually end up
on the requested node.

It implements the ccr clean_session action with this client.

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

@@ -25,6 +25,7 @@ import org.elasticsearch.action.ActionRequest;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.client.support.AbstractClient;
+import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.threadpool.ThreadPool;
 
@@ -45,14 +46,19 @@ final class RemoteClusterAwareClient extends AbstractClient {
     protected <Request extends ActionRequest, Response extends ActionResponse>
     void doExecute(Action<Response> action, Request request, ActionListener<Response> listener) {
         remoteClusterService.ensureConnected(clusterAlias, ActionListener.wrap(res -> {
-            Transport.Connection connection = remoteClusterService.getConnection(clusterAlias);
+            Transport.Connection connection;
+            if (request instanceof RemoteClusterAwareRequest) {
+                DiscoveryNode preferredTargetNode = ((RemoteClusterAwareRequest) request).getPreferredTargetNode();
+                connection = remoteClusterService.getConnection(preferredTargetNode, clusterAlias);
+            } else {
+                connection = remoteClusterService.getConnection(clusterAlias);
+            }
             service.sendRequest(connection, action.name(), request, TransportRequestOptions.EMPTY,
                 new ActionListenerResponseHandler<>(listener, action.getResponseReader()));
         },
         listener::onFailure));
     }
 
-
     @Override
     public void close() {
         // do nothing

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

@@ -0,0 +1,35 @@
+/*
+ * 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.elasticsearch.cluster.node.DiscoveryNode;
+
+public interface RemoteClusterAwareRequest {
+
+    /**
+     * Returns the preferred discovery node for this request. The remote cluster client will attempt to send
+     * this request directly to this node. Otherwise, it will send the request as a proxy action that will
+     * be routed by the remote cluster to this node.
+     *
+     * @return preferred discovery node
+     */
+    DiscoveryNode getPreferredTargetNode();
+
+}

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/repositories/ClearCcrRestoreSessionAction.java

@@ -7,24 +7,19 @@
 package org.elasticsearch.xpack.ccr.action.repositories;
 
 import org.elasticsearch.action.Action;
-import org.elasticsearch.action.FailedNodeException;
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.support.ActionFilters;
-import org.elasticsearch.action.support.nodes.BaseNodeResponse;
-import org.elasticsearch.action.support.nodes.BaseNodesResponse;
-import org.elasticsearch.action.support.nodes.TransportNodesAction;
-import org.elasticsearch.cluster.ClusterName;
-import org.elasticsearch.cluster.node.DiscoveryNode;
-import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.action.support.HandledTransportAction;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.io.stream.StreamInput;
-import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.tasks.Task;
 import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.transport.TransportActionProxy;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.ccr.repository.CcrRestoreSourceService;
 
-import java.io.IOException;
-import java.util.List;
-
 public class ClearCcrRestoreSessionAction extends Action<ClearCcrRestoreSessionAction.ClearCcrRestoreSessionResponse> {
 
     public static final ClearCcrRestoreSessionAction INSTANCE = new ClearCcrRestoreSessionAction();
@@ -36,86 +31,47 @@ public class ClearCcrRestoreSessionAction extends Action<ClearCcrRestoreSessionA
 
     @Override
     public ClearCcrRestoreSessionResponse newResponse() {
-        return new ClearCcrRestoreSessionResponse();
+        throw new UnsupportedOperationException();
     }
 
-    public static class TransportDeleteCcrRestoreSessionAction extends TransportNodesAction<ClearCcrRestoreSessionRequest,
-        ClearCcrRestoreSessionResponse, ClearCcrRestoreSessionRequest.Request, Response> {
+    @Override
+    public Writeable.Reader<ClearCcrRestoreSessionResponse> getResponseReader() {
+        return ClearCcrRestoreSessionResponse::new;
+    }
+
+    public static class TransportDeleteCcrRestoreSessionAction
+        extends HandledTransportAction<ClearCcrRestoreSessionRequest, ClearCcrRestoreSessionResponse> {
 
         private final CcrRestoreSourceService ccrRestoreService;
+        private final ThreadPool threadPool;
 
         @Inject
-        public TransportDeleteCcrRestoreSessionAction(ThreadPool threadPool, ClusterService clusterService, ActionFilters actionFilters,
-                                                      TransportService transportService, CcrRestoreSourceService ccrRestoreService) {
-            super(NAME, threadPool, clusterService, transportService, actionFilters, ClearCcrRestoreSessionRequest::new,
-                ClearCcrRestoreSessionRequest.Request::new, ThreadPool.Names.GENERIC, Response.class);
+        public TransportDeleteCcrRestoreSessionAction(ActionFilters actionFilters, TransportService transportService,
+                                                      CcrRestoreSourceService ccrRestoreService) {
+            super(NAME, transportService, actionFilters, ClearCcrRestoreSessionRequest::new);
+            TransportActionProxy.registerProxyAction(transportService, NAME, ClearCcrRestoreSessionResponse::new);
             this.ccrRestoreService = ccrRestoreService;
+            this.threadPool = transportService.getThreadPool();
         }
 
         @Override
-        protected ClearCcrRestoreSessionResponse newResponse(ClearCcrRestoreSessionRequest request, List<Response> responses,
-                                                             List<FailedNodeException> failures) {
-            return new ClearCcrRestoreSessionResponse(clusterService.getClusterName(), responses, failures);
-        }
-
-        @Override
-        protected ClearCcrRestoreSessionRequest.Request newNodeRequest(String nodeId, ClearCcrRestoreSessionRequest request) {
-            return request.getRequest();
-        }
-
-        @Override
-        protected Response newNodeResponse() {
-            return new Response();
-        }
-
-        @Override
-        protected Response nodeOperation(ClearCcrRestoreSessionRequest.Request request) {
-            ccrRestoreService.closeSession(request.getSessionUUID());
-            return new Response(clusterService.localNode());
+        protected void doExecute(Task task, ClearCcrRestoreSessionRequest request,
+                                 ActionListener<ClearCcrRestoreSessionResponse> listener) {
+            // TODO: Currently blocking actions might occur in the session closed callbacks. This dispatch
+            //  may be unnecessary when we remove these callbacks.
+            threadPool.generic().execute(() ->  {
+                ccrRestoreService.closeSession(request.getSessionUUID());
+                listener.onResponse(new ClearCcrRestoreSessionResponse());
+            });
         }
     }
 
-    public static class Response extends BaseNodeResponse {
-
-        private Response() {
-        }
-
-        private Response(StreamInput in) throws IOException {
-            readFrom(in);
-        }
-
-        private Response(DiscoveryNode node) {
-            super(node);
-        }
-
-        @Override
-        public void writeTo(StreamOutput out) throws IOException {
-            super.writeTo(out);
-        }
-
-        @Override
-        public void readFrom(StreamInput in) throws IOException {
-            super.readFrom(in);
-        }
-    }
-
-    public static class ClearCcrRestoreSessionResponse extends BaseNodesResponse<Response> {
+    public static class ClearCcrRestoreSessionResponse extends ActionResponse {
 
         ClearCcrRestoreSessionResponse() {
         }
 
-        ClearCcrRestoreSessionResponse(ClusterName clusterName, List<Response> chunkResponses, List<FailedNodeException> failures) {
-            super(clusterName, chunkResponses, failures);
-        }
-
-        @Override
-        protected List<Response> readNodesFrom(StreamInput in) throws IOException {
-            return in.readList(Response::new);
-        }
-
-        @Override
-        protected void writeNodesTo(StreamOutput out, List<Response> nodes) throws IOException {
-            out.writeList(nodes);
+        ClearCcrRestoreSessionResponse(StreamInput in) {
         }
     }
 }

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/repositories/ClearCcrRestoreSessionRequest.java

@@ -6,68 +6,52 @@
 
 package org.elasticsearch.xpack.ccr.action.repositories;
 
-import org.elasticsearch.action.support.nodes.BaseNodeRequest;
-import org.elasticsearch.action.support.nodes.BaseNodesRequest;
+import org.elasticsearch.action.ActionRequest;
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.transport.RemoteClusterAwareRequest;
+import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 
 import java.io.IOException;
 
-public class ClearCcrRestoreSessionRequest extends BaseNodesRequest<ClearCcrRestoreSessionRequest> {
+public class ClearCcrRestoreSessionRequest extends ActionRequest implements RemoteClusterAwareRequest {
 
-    private Request request;
+    private DiscoveryNode node;
+    private String sessionUUID;
 
-    ClearCcrRestoreSessionRequest() {
+    ClearCcrRestoreSessionRequest(StreamInput in) throws IOException {
+        super.readFrom(in);
+        sessionUUID = in.readString();
     }
 
-    public ClearCcrRestoreSessionRequest(String nodeId, Request request) {
-        super(nodeId);
-        this.request = request;
+    public ClearCcrRestoreSessionRequest(String sessionUUID, DiscoveryNode node) {
+        this.sessionUUID = sessionUUID;
+        this.node = node;
     }
 
     @Override
-    public void readFrom(StreamInput streamInput) throws IOException {
-        super.readFrom(streamInput);
-        request = new Request();
-        request.readFrom(streamInput);
+    public ActionRequestValidationException validate() {
+        return null;
     }
 
     @Override
-    public void writeTo(StreamOutput streamOutput) throws IOException {
-        super.writeTo(streamOutput);
-        request.writeTo(streamOutput);
+    public void readFrom(StreamInput in) throws IOException {
+        throw new UnsupportedOperationException();
     }
 
-    public Request getRequest() {
-        return request;
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+        out.writeString(sessionUUID);
     }
 
-    public static class Request extends BaseNodeRequest {
-
-        private String sessionUUID;
-
-        Request() {
-        }
-
-        public Request(String nodeId, String sessionUUID) {
-            super(nodeId);
-            this.sessionUUID = sessionUUID;
-        }
-
-        @Override
-        public void readFrom(StreamInput in) throws IOException {
-            super.readFrom(in);
-            sessionUUID = in.readString();
-        }
-
-        @Override
-        public void writeTo(StreamOutput out) throws IOException {
-            super.writeTo(out);
-            out.writeString(sessionUUID);
-        }
+    String getSessionUUID() {
+        return sessionUUID;
+    }
 
-        public String getSessionUUID() {
-            return sessionUUID;
-        }
+    @Override
+    public DiscoveryNode getPreferredTargetNode() {
+        return node;
     }
 }

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/repositories/PutCcrRestoreSessionAction.java

@@ -12,6 +12,7 @@ import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.action.support.single.shard.TransportSingleShardAction;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.routing.ShardsIterator;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.inject.Inject;
@@ -70,7 +71,7 @@ public class PutCcrRestoreSessionAction extends Action<PutCcrRestoreSessionActio
                 throw new ShardNotFoundException(shardId);
             }
             ccrRestoreService.openSession(request.getSessionUUID(), indexShard);
-            return new PutCcrRestoreSessionResponse(indexShard.routingEntry().currentNodeId());
+            return new PutCcrRestoreSessionResponse(clusterService.localNode());
         }
 
         @Override
@@ -93,34 +94,34 @@ public class PutCcrRestoreSessionAction extends Action<PutCcrRestoreSessionActio
 
     public static class PutCcrRestoreSessionResponse extends ActionResponse {
 
-        private String nodeId;
+        private DiscoveryNode node;
 
         PutCcrRestoreSessionResponse() {
         }
 
-        PutCcrRestoreSessionResponse(String nodeId) {
-            this.nodeId = nodeId;
+        PutCcrRestoreSessionResponse(DiscoveryNode node) {
+            this.node = node;
         }
 
         PutCcrRestoreSessionResponse(StreamInput in) throws IOException {
             super(in);
-            nodeId = in.readString();
+            node = new DiscoveryNode(in);
         }
 
         @Override
         public void readFrom(StreamInput in) throws IOException {
             super.readFrom(in);
-            nodeId = in.readString();
+            node = new DiscoveryNode(in);
         }
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             super.writeTo(out);
-            out.writeString(nodeId);
+            node.writeTo(out);
         }
 
-        public String getNodeId() {
-            return nodeId;
+        public DiscoveryNode getNode() {
+            return node;
         }
     }
 }

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/repository/CcrRepository.java

@@ -253,9 +253,9 @@ public class CcrRepository extends AbstractLifecycleComponent implements Reposit
         String sessionUUID = UUIDs.randomBase64UUID();
         PutCcrRestoreSessionAction.PutCcrRestoreSessionResponse response = remoteClient.execute(PutCcrRestoreSessionAction.INSTANCE,
             new PutCcrRestoreSessionRequest(sessionUUID, leaderShardId, recoveryMetadata)).actionGet();
-        String nodeId = response.getNodeId();
+        DiscoveryNode node = response.getNode();
         // TODO: Implement file restore
-        closeSession(remoteClient, nodeId, sessionUUID);
+        closeSession(remoteClient, node, sessionUUID);
         maybeUpdateMappings(client, remoteClient, leaderIndex, indexShard.indexSettings());
     }
 
@@ -278,13 +278,9 @@ public class CcrRepository extends AbstractLifecycleComponent implements Reposit
         }
     }
 
-    private void closeSession(Client remoteClient, String nodeId, String sessionUUID) {
-        ClearCcrRestoreSessionRequest clearRequest = new ClearCcrRestoreSessionRequest(nodeId,
-            new ClearCcrRestoreSessionRequest.Request(nodeId, sessionUUID));
+    private void closeSession(Client remoteClient, DiscoveryNode node, String sessionUUID) {
+        ClearCcrRestoreSessionRequest clearRequest = new ClearCcrRestoreSessionRequest(sessionUUID, node);
         ClearCcrRestoreSessionAction.ClearCcrRestoreSessionResponse response =
             remoteClient.execute(ClearCcrRestoreSessionAction.INSTANCE, clearRequest).actionGet();
-        if (response.hasFailures()) {
-            throw response.failures().get(0);
-        }
     }
 }