Currently, `TransportGetShutdownStatusAction` is executed in a transport thread, this action can do a substantial amount of work (O(# shards) in some cases) in the transport thread preventing pending transport tasks to make progress and potentially causing cluster instability. This action should be dispatched into a different thread pool to avoid such issues.
x-pack/plugin/shutdown/src/main/java/org/elasticsearch/xpack/shutdown/TransportGetShutdownStatusAction.java
/*
 * 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; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.xpack.shutdown;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.support.ActionFilters;
import org.elasticsearch.action.support.master.TransportMasterNodeAction;
import org.elasticsearch.cluster.ClusterInfoService;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.block.ClusterBlockException;
import org.elasticsearch.cluster.block.ClusterBlockLevel;
import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
import org.elasticsearch.cluster.metadata.LifecycleExecutionState;
import org.elasticsearch.cluster.metadata.NodesShutdownMetadata;
import org.elasticsearch.cluster.metadata.ShutdownPersistentTasksStatus;
import org.elasticsearch.cluster.metadata.ShutdownPluginsStatus;
import org.elasticsearch.cluster.metadata.ShutdownShardMigrationStatus;
import org.elasticsearch.cluster.metadata.SingleNodeShutdownMetadata;
import org.elasticsearch.cluster.routing.ShardRouting;