Add the locking mechanism before the check for whether the coordinator already exists

citus-tools

@@ -0,0 +1 @@
+Subproject commit 3376bd6845f0614908ed304f5033bd644c82d3bf

src/backend/distributed/metadata/node_metadata.c

@@ -217,6 +217,9 @@ citus_set_coordinator_host(PG_FUNCTION_ARGS)
 		EnsureTransactionalMetadataSyncMode();
 	}
 
+	/* prevent concurrent modification */
+	LockRelationOid(DistNodeRelationId(), RowExclusiveLock);
+
 	bool isCoordinatorInMetadata = false;
 	WorkerNode *coordinatorNode = PrimaryNodeForGroup(COORDINATOR_GROUP_ID,
 													  &isCoordinatorInMetadata);