Adding a transport action to get cluster formation info (#87306)

This commit exposes ClusterFormationFailureHelper.ClusterFormationState in a transport action (ClusterFormationInfoAction), with the intention that it be used as part of the master stability health check.

docs/changelog/87306.yaml

@@ -0,0 +1,5 @@
+pr: 87306
+summary: Adding a transport action to get cluster formation info
+area: Health
+type: enhancement
+issues: []

server/src/main/java/org/elasticsearch/action/ActionModule.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.action.admin.cluster.configuration.ClearVotingConfigExclusionsAction;
 import org.elasticsearch.action.admin.cluster.configuration.TransportAddVotingConfigExclusionsAction;
 import org.elasticsearch.action.admin.cluster.configuration.TransportClearVotingConfigExclusionsAction;
+import org.elasticsearch.action.admin.cluster.coordination.ClusterFormationInfoAction;
 import org.elasticsearch.action.admin.cluster.coordination.MasterHistoryAction;
 import org.elasticsearch.action.admin.cluster.desirednodes.DeleteDesiredNodesAction;
 import org.elasticsearch.action.admin.cluster.desirednodes.GetDesiredNodesAction;
@@ -555,6 +556,7 @@ public <Request extends ActionRequest, Response extends ActionResponse> void reg
         actions.register(ClusterGetSettingsAction.INSTANCE, TransportClusterGetSettingsAction.class);
         actions.register(ClusterRerouteAction.INSTANCE, TransportClusterRerouteAction.class);
         actions.register(ClusterSearchShardsAction.INSTANCE, TransportClusterSearchShardsAction.class);
+        actions.register(ClusterFormationInfoAction.INSTANCE, ClusterFormationInfoAction.TransportAction.class);
         actions.register(PendingClusterTasksAction.INSTANCE, TransportPendingClusterTasksAction.class);
         actions.register(PutRepositoryAction.INSTANCE, TransportPutRepositoryAction.class);
         actions.register(GetRepositoriesAction.INSTANCE, TransportGetRepositoriesAction.class);

server/src/main/java/org/elasticsearch/action/admin/cluster/coordination/ClusterFormationInfoAction.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.action.admin.cluster.coordination;
+
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ActionRequest;
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.action.ActionResponse;
+import org.elasticsearch.action.ActionType;
+import org.elasticsearch.action.support.ActionFilters;
+import org.elasticsearch.action.support.HandledTransportAction;
+import org.elasticsearch.cluster.coordination.ClusterFormationFailureHelper;
+import org.elasticsearch.cluster.coordination.Coordinator;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.tasks.Task;
+import org.elasticsearch.transport.TransportService;
+
+import java.io.IOException;
+import java.util.Objects;
+
+/**
+ * This class is used to fetch the ClusterFormationState from another node. The ClusterFormationState provides information about why that
+ * node thinks that cluster formation has failed.
+ */
+public class ClusterFormationInfoAction extends ActionType<ClusterFormationInfoAction.Response> {
+
+    public static final ClusterFormationInfoAction INSTANCE = new ClusterFormationInfoAction();
+    public static final String NAME = "cluster:internal/formation/info";
+
+    private ClusterFormationInfoAction() {
+        super(NAME, ClusterFormationInfoAction.Response::new);
+    }
+
+    public static class Request extends ActionRequest {
+
+        public Request() {}
+
+        @Override
+        public ActionRequestValidationException validate() {
+            return null;
+        }
+
+        public Request(StreamInput in) throws IOException {
+            super(in);
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            super.writeTo(out);
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            // There are no parameters, so all instances of this class are equal
+            if (this == o) {
+                return true;
+            }
+            return o != null && getClass() == o.getClass();
+        }
+
+        @Override
+        public int hashCode() {
+            // There are no parameters, so all instances of this class are equal
+            return 1;
+        }
+
+    }
+
+    public static class Response extends ActionResponse {
+
+        private final ClusterFormationFailureHelper.ClusterFormationState clusterFormationState;
+
+        public Response(StreamInput in) throws IOException {
+            super(in);
+            clusterFormationState = new ClusterFormationFailureHelper.ClusterFormationState(in);
+        }
+
+        public Response(ClusterFormationFailureHelper.ClusterFormationState clusterFormationState) {
+            this.clusterFormationState = clusterFormationState;
+        }
+
+        public ClusterFormationFailureHelper.ClusterFormationState getClusterFormationState() {
+            return clusterFormationState;
+        }
+
+        @Override
+        public void writeTo(StreamOutput out) throws IOException {
+            clusterFormationState.writeTo(out);
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (o == null || getClass() != o.getClass()) {
+                return false;
+            }
+            ClusterFormationInfoAction.Response response = (ClusterFormationInfoAction.Response) o;
+            return clusterFormationState.equals(response.clusterFormationState);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(clusterFormationState);
+        }
+    }
+
+    /**
+     * This transport action fetches the ClusterFormationState from a remote node.
+     */
+    public static class TransportAction extends HandledTransportAction<
+        ClusterFormationInfoAction.Request,
+        ClusterFormationInfoAction.Response> {
+        private final Coordinator coordinator;
+
+        @Inject
+        public TransportAction(TransportService transportService, ActionFilters actionFilters, Coordinator coordinator) {
+            super(ClusterFormationInfoAction.NAME, transportService, actionFilters, ClusterFormationInfoAction.Request::new);
+            this.coordinator = coordinator;
+        }
+
+        @Override
+        protected void doExecute(
+            Task task,
+            ClusterFormationInfoAction.Request request,
+            ActionListener<ClusterFormationInfoAction.Response> listener
+        ) {
+            listener.onResponse(new ClusterFormationInfoAction.Response(coordinator.getClusterFormationState()));
+        }
+    }
+
+}