fixup! ZOOKEEPER-4475: Fix NodeChildrenChanged delivered to recursive…

… watcher
apache · Jun 29, 2022 · f7bb53e · f7bb53e
1 parent de934cc
commit f7bb53e
Show file tree

Hide file tree

Showing 2 changed files with 10 additions and 1 deletion.
diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/ZKWatchManager.java b/zookeeper-server/src/main/java/org/apache/zookeeper/ZKWatchManager.java
@@ -446,6 +446,11 @@ private void addPersistentWatches(String clientPath, Watcher.Event.EventType typ
         synchronized (persistentWatches) {
             addTo(persistentWatches.get(clientPath), result);
         }
+        // The semantics of persistent recursive watch promise no child events on descendant nodes. But this
+        // could not be achieved in server side as there could be standard child watches on descendants of node
+        // being watched in persistent recursive mode. This means server could fire child events on descendant
+        // nodes due to standard child watches on these nodes. So we have to filter out child events for persistent
+        // recursive watches on client side.
         if (type == Watcher.Event.EventType.NodeChildrenChanged) {
             return;
         }

diff --git a/zookeeper-server/src/test/java/org/apache/zookeeper/test/PersistentRecursiveWatcherTest.java b/zookeeper-server/src/test/java/org/apache/zookeeper/test/PersistentRecursiveWatcherTest.java
@@ -121,13 +121,17 @@ public void testNoChildEvents() throws Exception {
 
             zk.addWatch("/", persistentWatcher, PERSISTENT_RECURSIVE);
 
-            zk.getChildren("/a", true);
+            BlockingQueue<WatchedEvent> childEvents = new LinkedBlockingQueue<>();
+            zk.getChildren("/a", childEvents::add);
 
             zk.create("/a/b", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
             zk.create("/a/b/c", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
 
+            assertEvent(childEvents, Watcher.Event.EventType.NodeChildrenChanged, "/a");
+
             assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a/b");
             assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a/b/c");
+            assertTrue(events.isEmpty());
         }
     }