Run TransportExplainLifecycleAction on local node (elastic#122885)

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 elastic#101805

Author: nielsbauman

docs/changelog/122885.yaml

@@ -0,0 +1,5 @@
+pr: 122885
+summary: Run `TransportExplainLifecycleAction` on local node
+area: ILM+SLM
+type: enhancement
+issues: []

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ExplainLifecycleRequest.java

@@ -7,15 +7,22 @@
 
 package org.elasticsearch.xpack.core.ilm;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
-import org.elasticsearch.action.support.master.info.ClusterInfoRequest;
+import org.elasticsearch.action.support.local.LocalClusterStateRequest;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
-import org.elasticsearch.common.io.stream.StreamOutput;
 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 java.io.IOException;
 import java.util.Arrays;
+import java.util.Map;
 import java.util.Objects;
 
 /**
@@ -24,26 +31,58 @@
  * Multiple indices may be queried in the same request using the
  * {@link #indices(String...)} method
  */
-public class ExplainLifecycleRequest extends ClusterInfoRequest<ExplainLifecycleRequest> {
+public class ExplainLifecycleRequest extends LocalClusterStateRequest implements IndicesRequest.Replaceable {
 
+    private String[] indices = Strings.EMPTY_ARRAY;
+    private IndicesOptions indicesOptions;
     private boolean onlyErrors = false;
     private boolean onlyManaged = false;
 
     public ExplainLifecycleRequest(TimeValue masterTimeout) {
-        super(masterTimeout, IndicesOptions.strictExpandOpen());
+        super(masterTimeout);
+        indicesOptions = IndicesOptions.strictExpandOpen();
     }
 
+    /**
+     * 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 ExplainLifecycleRequest(StreamInput in) throws IOException {
         super(in);
+        indices = in.readStringArray();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readStringArray();
+        }
+        indicesOptions = IndicesOptions.readIndicesOptions(in);
         onlyErrors = in.readBoolean();
         onlyManaged = in.readBoolean();
     }
 
     @Override
-    public void writeTo(StreamOutput out) throws IOException {
-        super.writeTo(out);
-        out.writeBoolean(onlyErrors);
-        out.writeBoolean(onlyManaged);
+    public ExplainLifecycleRequest indices(String... indices) {
+        this.indices = indices;
+        return this;
+    }
+
+    public ExplainLifecycleRequest indicesOptions(IndicesOptions indicesOptions) {
+        this.indicesOptions = indicesOptions;
+        return this;
+    }
+
+    @Override
+    public String[] indices() {
+        return indices;
+    }
+
+    @Override
+    public IndicesOptions indicesOptions() {
+        return indicesOptions;
+    }
+
+    @Override
+    public boolean includeDataStreams() {
+        return true;
     }
 
     public boolean onlyErrors() {
@@ -69,6 +108,11 @@ public ActionRequestValidationException validate() {
         return null;
     }
 
+    @Override
+    public Task createTask(long id, String type, String action, TaskId parentTaskId, Map<String, String> headers) {
+        return new CancellableTask(id, type, action, "", parentTaskId, headers);
+    }
+
     @Override
     public int hashCode() {
         return Objects.hash(Arrays.hashCode(indices()), indicesOptions(), onlyErrors, onlyManaged);

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/ExplainLifecycleResponse.java

@@ -9,9 +9,8 @@
 
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.util.Maps;
+import org.elasticsearch.core.UpdateForV10;
 import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -32,17 +31,6 @@ public class ExplainLifecycleResponse extends ActionResponse implements ToXConte
 
     private final Map<String, IndexLifecycleExplainResponse> indexResponses;
 
-    public ExplainLifecycleResponse(StreamInput in) throws IOException {
-        super(in);
-        int size = in.readVInt();
-        Map<String, IndexLifecycleExplainResponse> indexResponses = Maps.newMapWithExpectedSize(size);
-        for (int i = 0; i < size; i++) {
-            IndexLifecycleExplainResponse indexResponse = new IndexLifecycleExplainResponse(in);
-            indexResponses.put(indexResponse.getIndex(), indexResponse);
-        }
-        this.indexResponses = indexResponses;
-    }
-
     public ExplainLifecycleResponse(Map<String, IndexLifecycleExplainResponse> indexResponses) {
         this.indexResponses = indexResponses;
     }
@@ -69,6 +57,11 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         return builder;
     }
 
+    /**
+     * 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 {
         out.writeCollection(indexResponses.values());

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ilm/ExplainLifecycleRequestTests.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.rest.BaseRestHandler;
 import org.elasticsearch.rest.RestRequest;
+import org.elasticsearch.rest.action.RestCancellableNodeClient;
 import org.elasticsearch.rest.action.RestToXContentListener;
 import org.elasticsearch.xpack.core.ilm.ExplainLifecycleRequest;
 import org.elasticsearch.xpack.core.ilm.action.ExplainLifecycleAction;
@@ -41,6 +42,10 @@ protected RestChannelConsumer prepareRequest(RestRequest restRequest, NodeClient
         explainLifecycleRequest.indicesOptions(IndicesOptions.fromRequest(restRequest, IndicesOptions.strictExpandOpen()));
         explainLifecycleRequest.onlyManaged(restRequest.paramAsBoolean("only_managed", false));
         explainLifecycleRequest.onlyErrors(restRequest.paramAsBoolean("only_errors", false));
-        return channel -> client.execute(ExplainLifecycleAction.INSTANCE, explainLifecycleRequest, new RestToXContentListener<>(channel));
+        return channel -> new RestCancellableNodeClient(client, restRequest.getHttpChannel()).execute(
+            ExplainLifecycleAction.INSTANCE,
+            explainLifecycleRequest,
+            new RestToXContentListener<>(channel)
+        );
     }
 }