From 743db209e91ecd0c389a2b271dc05252bf5b9f91 Mon Sep 17 00:00:00 2001
From: David Turner <david.turner@elastic.co>
Date: Tue, 14 May 2019 10:34:20 +0100
Subject: [PATCH] Log cluster UUID when committed (#42065)

Today we do not expose the cluster UUID in any logs by default, but it would be
useful to see it. For instance if a user starts multiple nodes as separate
clusters then they will silently remain as separate clusters even if they are
subsequently reconfigured to look like a single cluster. This change logs the
committed cluster UUID the first time the node encounters it.
---
 .../cluster/coordination/CoordinationState.java             | 1 +
 .../org/elasticsearch/cluster/coordination/Coordinator.java | 6 +++++-
 server/src/main/java/org/elasticsearch/node/Node.java       | 6 ++++--
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationState.java b/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationState.java
index a38a383b269d5..ac75c83c19a26 100644
--- a/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationState.java
+++ b/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationState.java
@@ -480,6 +480,7 @@ default void markLastAcceptedStateAsCommitted() {
                     metaDataBuilder = MetaData.builder(lastAcceptedState.metaData());
                 }
                 metaDataBuilder.clusterUUIDCommitted(true);
+                logger.info("cluster UUID set to [{}]", lastAcceptedState.metaData().clusterUUID());
             }
             if (metaDataBuilder != null) {
                 setLastAcceptedState(ClusterState.builder(lastAcceptedState).metaData(metaDataBuilder).build());
diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java b/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
index 457cfcb15486e..6304588e3121a 100644
--- a/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
+++ b/server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
@@ -647,7 +647,11 @@ protected void doStart() {
             coordinationState.set(new CoordinationState(settings, getLocalNode(), persistedState));
             peerFinder.setCurrentTerm(getCurrentTerm());
             configuredHostsResolver.start();
-            VotingConfiguration votingConfiguration = coordinationState.get().getLastAcceptedState().getLastCommittedConfiguration();
+            final ClusterState lastAcceptedState = coordinationState.get().getLastAcceptedState();
+            if (lastAcceptedState.metaData().clusterUUIDCommitted()) {
+                logger.info("cluster UUID [{}]", lastAcceptedState.metaData().clusterUUID());
+            }
+            final VotingConfiguration votingConfiguration = lastAcceptedState.getLastCommittedConfiguration();
             if (singleNodeDiscovery &&
                 votingConfiguration.isEmpty() == false &&
                 votingConfiguration.hasQuorum(Collections.singleton(getLocalNode().getId())) == false) {
diff --git a/server/src/main/java/org/elasticsearch/node/Node.java b/server/src/main/java/org/elasticsearch/node/Node.java
index 4b77c06447836..f0ec86f8cb84c 100644
--- a/server/src/main/java/org/elasticsearch/node/Node.java
+++ b/server/src/main/java/org/elasticsearch/node/Node.java
@@ -40,6 +40,7 @@
 import org.elasticsearch.cluster.ClusterInfo;
 import org.elasticsearch.cluster.ClusterInfoService;
 import org.elasticsearch.cluster.ClusterModule;
+import org.elasticsearch.cluster.ClusterName;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.ClusterStateObserver;
 import org.elasticsearch.cluster.InternalClusterInfoService;
@@ -271,8 +272,9 @@ protected Node(
 
             nodeEnvironment = new NodeEnvironment(tmpSettings, environment);
             resourcesToClose.add(nodeEnvironment);
-            logger.info("node name [{}], node ID [{}]",
-                    NODE_NAME_SETTING.get(tmpSettings), nodeEnvironment.nodeId());
+            logger.info("node name [{}], node ID [{}], cluster name [{}]",
+                    NODE_NAME_SETTING.get(tmpSettings), nodeEnvironment.nodeId(),
+                    ClusterName.CLUSTER_NAME_SETTING.get(tmpSettings).value());
 
             final JvmInfo jvmInfo = JvmInfo.jvmInfo();
             logger.info(