Skip shard management code when updating cluster state on client/tribe nodes (#20731)

IndicesClusterStateService and IndicesStore are responsible for synchronizing local shard state based on incoming cluster state updates. On client/tribe nodes, which don't store any such shard/index data/metadata, all of the logic that computes which data is to be deleted, which shards to be initialized etc. can be completely skipped, saving precious CPU cycles.

core/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java

@@ -148,12 +148,17 @@ public class IndicesClusterStateService extends AbstractLifecycleComponent imple
 
     @Override
     protected void doStart() {
-        clusterService.addFirst(this);
+        // Doesn't make sense to manage shards on non-master and non-data nodes
+        if (DiscoveryNode.isDataNode(settings) || DiscoveryNode.isMasterNode(settings)) {
+            clusterService.addFirst(this);
+        }
     }
 
     @Override
     protected void doStop() {
-        clusterService.remove(this);
+        if (DiscoveryNode.isDataNode(settings) || DiscoveryNode.isMasterNode(settings)) {
+            clusterService.remove(this);
+        }
     }
 
     @Override

core/src/main/java/org/elasticsearch/indices/store/IndicesStore.java

@@ -94,12 +94,17 @@ public class IndicesStore extends AbstractComponent implements ClusterStateListe
         this.threadPool = threadPool;
         transportService.registerRequestHandler(ACTION_SHARD_EXISTS, ShardActiveRequest::new, ThreadPool.Names.SAME, new ShardActiveRequestHandler());
         this.deleteShardTimeout = INDICES_STORE_DELETE_SHARD_TIMEOUT.get(settings);
-        clusterService.addLast(this);
+        // Doesn't make sense to delete shards on non-data nodes
+        if (DiscoveryNode.isDataNode(settings)) {
+            clusterService.add(this);
+        }
     }
 
     @Override
     public void close() {
-        clusterService.remove(this);
+        if (DiscoveryNode.isDataNode(settings)) {
+            clusterService.remove(this);
+        }
     }
 
     @Override