Run TransportGetWatcherSettingsAction on local node (#122857)

This action solely needs the cluster state, it can run on any node.
Additionally, it needs to be cancellable to avoid doing unnecessary work
after a client failure or timeout.

Relates #101805

Author: nielsbauman

docs/changelog/122857.yaml

@@ -0,0 +1,5 @@
+pr: 122857
+summary: Run `TransportGetWatcherSettingsAction` on local node
+area: Watcher
+type: enhancement
+issues: []

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/transport/actions/put/GetWatcherSettingsAction.java

@@ -11,15 +11,20 @@
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionType;
-import org.elasticsearch.action.support.master.MasterNodeReadRequest;
+import org.elasticsearch.action.support.local.LocalClusterStateRequest;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.core.UpdateForV10;
+import org.elasticsearch.tasks.CancellableTask;
+import org.elasticsearch.tasks.Task;
+import org.elasticsearch.tasks.TaskId;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
 
 import java.io.IOException;
+import java.util.Map;
 
 public class GetWatcherSettingsAction extends ActionType<GetWatcherSettingsAction.Response> {
 
@@ -30,12 +35,17 @@ public GetWatcherSettingsAction() {
         super(NAME);
     }
 
-    public static class Request extends MasterNodeReadRequest<Request> {
+    public static class Request extends LocalClusterStateRequest {
 
         public Request(TimeValue masterNodeTimeout) {
             super(masterNodeTimeout);
         }
 
+        /**
+         * NB prior to 9.0 this was a TransportMasterNodeReadAction so for BwC we must remain able to read these requests until
+         * we no longer need to support calling this action remotely.
+         */
+        @UpdateForV10(owner = UpdateForV10.Owner.DATA_MANAGEMENT)
         public static Request readFrom(StreamInput in) throws IOException {
             if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
                 return new Request(in);
@@ -49,15 +59,13 @@ private Request(StreamInput in) throws IOException {
         }
 
         @Override
-        public void writeTo(StreamOutput out) throws IOException {
-            if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
-                super.writeTo(out);
-            }
+        public ActionRequestValidationException validate() {
+            return null;
         }
 
         @Override
-        public ActionRequestValidationException validate() {
-            return null;
+        public Task createTask(long id, String type, String action, TaskId parentTaskId, Map<String, String> headers) {
+            return new CancellableTask(id, type, action, "", parentTaskId, headers);
         }
     }
 
@@ -69,10 +77,11 @@ public Response(Settings settings) {
             this.settings = settings;
         }
 
-        public Response(StreamInput in) throws IOException {
-            this.settings = Settings.readSettingsFromStream(in);
-        }
-
+        /**
+         * NB prior to 9.0 this was a TransportMasterNodeReadAction so for BwC we must remain able to write these responses until
+         * we no longer need to support calling this action remotely.
+         */
+        @UpdateForV10(owner = UpdateForV10.Owner.DATA_MANAGEMENT)
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             this.settings.writeTo(out);

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/rest/action/RestGetWatcherSettingsAction.java

@@ -11,6 +11,7 @@
 import org.elasticsearch.rest.BaseRestHandler;
 import org.elasticsearch.rest.RestRequest;
 import org.elasticsearch.rest.RestUtils;
+import org.elasticsearch.rest.action.RestCancellableNodeClient;
 import org.elasticsearch.rest.action.RestToXContentListener;
 import org.elasticsearch.xpack.core.watcher.transport.actions.put.GetWatcherSettingsAction;
 
@@ -37,6 +38,10 @@ public List<Route> routes() {
     @Override
     protected RestChannelConsumer prepareRequest(RestRequest request, NodeClient client) throws IOException {
         GetWatcherSettingsAction.Request req = new GetWatcherSettingsAction.Request(RestUtils.getMasterNodeTimeout(request));
-        return channel -> client.execute(GetWatcherSettingsAction.INSTANCE, req, new RestToXContentListener<>(channel));
+        return channel -> new RestCancellableNodeClient(client, request.getHttpChannel()).execute(
+            GetWatcherSettingsAction.INSTANCE,
+            req,
+            new RestToXContentListener<>(channel)
+        );
     }
 }

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/transport/actions/TransportGetWatcherSettingsAction.java

@@ -9,7 +9,8 @@
 
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.support.ActionFilters;
-import org.elasticsearch.action.support.master.TransportMasterNodeAction;
+import org.elasticsearch.action.support.ChannelActionListener;
+import org.elasticsearch.action.support.local.TransportLocalClusterStateAction;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.block.ClusterBlockException;
 import org.elasticsearch.cluster.block.ClusterBlockLevel;
@@ -18,9 +19,10 @@
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
+import org.elasticsearch.core.UpdateForV10;
 import org.elasticsearch.injection.guice.Inject;
+import org.elasticsearch.tasks.CancellableTask;
 import org.elasticsearch.tasks.Task;
-import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.core.watcher.transport.actions.put.GetWatcherSettingsAction;
 
@@ -30,40 +32,52 @@
 import static org.elasticsearch.xpack.watcher.transport.actions.TransportUpdateWatcherSettingsAction.WATCHER_INDEX_NAME;
 import static org.elasticsearch.xpack.watcher.transport.actions.TransportUpdateWatcherSettingsAction.WATCHER_INDEX_REQUEST;
 
-public class TransportGetWatcherSettingsAction extends TransportMasterNodeAction<
+public class TransportGetWatcherSettingsAction extends TransportLocalClusterStateAction<
     GetWatcherSettingsAction.Request,
     GetWatcherSettingsAction.Response> {
 
     private final IndexNameExpressionResolver indexNameExpressionResolver;
 
+    /**
+     * NB prior to 9.0 this was a TransportMasterNodeReadAction so for BwC it must be registered with the TransportService until
+     * we no longer need to support calling this action remotely.
+     */
+    @UpdateForV10(owner = UpdateForV10.Owner.DATA_MANAGEMENT)
+    @SuppressWarnings("this-escape")
     @Inject
     public TransportGetWatcherSettingsAction(
         TransportService transportService,
         ClusterService clusterService,
-        ThreadPool threadPool,
         ActionFilters actionFilters,
         IndexNameExpressionResolver indexNameExpressionResolver
     ) {
         super(
             GetWatcherSettingsAction.NAME,
-            transportService,
-            clusterService,
-            threadPool,
             actionFilters,
-            GetWatcherSettingsAction.Request::readFrom,
-            GetWatcherSettingsAction.Response::new,
+            transportService.getTaskManager(),
+            clusterService,
             EsExecutors.DIRECT_EXECUTOR_SERVICE
         );
         this.indexNameExpressionResolver = indexNameExpressionResolver;
+
+        transportService.registerRequestHandler(
+            actionName,
+            executor,
+            false,
+            true,
+            GetWatcherSettingsAction.Request::readFrom,
+            (request, channel, task) -> executeDirect(task, request, new ChannelActionListener<>(channel))
+        );
     }
 
     @Override
-    protected void masterOperation(
+    protected void localClusterStateOperation(
         Task task,
         GetWatcherSettingsAction.Request request,
         ClusterState state,
         ActionListener<GetWatcherSettingsAction.Response> listener
     ) {
+        ((CancellableTask) task).ensureNotCancelled();
         IndexMetadata metadata = state.metadata().index(WATCHER_INDEX_NAME);
         if (metadata == null) {
             listener.onResponse(new GetWatcherSettingsAction.Response(Settings.EMPTY));