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.

Author: DaveCTurner

server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationState.java

@@ -494,6 +494,7 @@ 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());

server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java

@@ -677,7 +677,11 @@ 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) {

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;
@@ -270,8 +271,9 @@ 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(