HBASE-28567 Race condition causes MetaRegionLocationCache to never se…

…t watcher to populate meta location (#5874)

Signed-off-by: Duo Zhang <zhangduo@apache.org>
Signed-off-by: Viraj Jasani <vjasani@apache.org>

hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKWatcher.java

@@ -460,6 +460,11 @@ public List<String> getMetaReplicaNodes() throws KeeperException {
   public List<String> getMetaReplicaNodesAndWatchChildren() throws KeeperException {
     List<String> childrenOfBaseNode =
       ZKUtil.listChildrenAndWatchForNewChildren(this, znodePaths.baseZNode);
+    // Need to throw here instead of returning an empty list if the base znode hasn't been created
+    // Caller should retry in that case, versus thinking the base znode has a watcher set
+    if (childrenOfBaseNode == null) {
+      keeperException(new KeeperException.NoNodeException(znodePaths.baseZNode));
+    }
     return filterMetaReplicaNodes(childrenOfBaseNode);
   }