From 3dcf1d54454346127f15aa6412e57d9825be9cc7 Mon Sep 17 00:00:00 2001
From: Yannick Welsch <yannick@welsch.lu>
Date: Tue, 4 Oct 2016 13:22:25 +0200
Subject: [PATCH] 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.
---
 .../indices/cluster/IndicesClusterStateService.java      | 9 +++++++--
 .../org/elasticsearch/indices/store/IndicesStore.java    | 9 +++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/core/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java b/core/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java
index 920de8ae467..96f0a98b991 100644
--- a/core/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java
+++ b/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
diff --git a/core/src/main/java/org/elasticsearch/indices/store/IndicesStore.java b/core/src/main/java/org/elasticsearch/indices/store/IndicesStore.java
index 439806b454b..372951bdfd5 100644
--- a/core/src/main/java/org/elasticsearch/indices/store/IndicesStore.java
+++ b/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