[jira] [Created] (ZOOKEEPER-4466) Watchers of different modes interfere on overlapping pathes

[Kezhu Wang (Jira)]

Kezhu Wang created ZOOKEEPER-4466:
-------------------------------------

             Summary: Watchers of different modes interfere on overlapping 
pathes
                 Key: ZOOKEEPER-4466
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4466
             Project: ZooKeeper
          Issue Type: Bug
          Components: java client, server
    Affects Versions: 3.6.3, 3.7, 3.6.4
            Reporter: Kezhu Wang


I used to think watchers of different modes are orthogonal. I found there are 
not, when I wrote tests for unfinished rust client. And I wrote [test 
cases|https://github.com/kezhuw/zookeeper/commit/79b05a95d2669a4acd16a4d544f24e2083a264f2#diff-8d31d27ea951fbc1f4fbda48d45748318f7124502839d825b77ad3fb8551bf43L152]
 in java and confirmed.

I copied test case here for evaluation. You also clone from [my 
fork|https://github.com/kezhuw/zookeeper/tree/watch-overlapping-path-with-different-modes-test-case].

{code:java}
    // 
zookeeper-server/src/test/java/org/apache/zookeeper/test/PersistentRecursiveWatcherTest.java

    @Test
    public void testPathOverlapWithStandardWatcher() throws Exception {
        try (ZooKeeper zk = createClient(new CountdownWatcher(), hostPort)) {
            CountDownLatch nodeCreated = new CountDownLatch(1);
            zk.addWatch("/a", persistentWatcher, PERSISTENT_RECURSIVE);
            zk.exists("/a", event -> nodeCreated.countDown());

            zk.create("/a", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, 
CreateMode.PERSISTENT);
            zk.create("/a/b", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, 
CreateMode.PERSISTENT);
            zk.delete("/a/b", -1);
            zk.delete("/a", -1);

            assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a");
            assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a/b");
            assertEvent(events, Watcher.Event.EventType.NodeDeleted, "/a/b");
            assertEvent(events, Watcher.Event.EventType.NodeDeleted, "/a");

            assertTrue(nodeCreated.await(5, TimeUnit.SECONDS));
        }
    }

    @Test
    public void testPathOverlapWithPersistentWatcher() throws Exception {
        try (ZooKeeper zk = createClient(new CountdownWatcher(), hostPort)) {
            zk.addWatch("/a", persistentWatcher, PERSISTENT_RECURSIVE);
            zk.addWatch("/a/b", event -> {}, PERSISTENT);
            zk.create("/a", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, 
CreateMode.PERSISTENT);
            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);
            zk.delete("/a/b/c", -1);
            zk.delete("/a/b", -1);
            zk.delete("/a", -1);
            assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a");
            assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a/b");
            assertEvent(events, Watcher.Event.EventType.NodeCreated, "/a/b/c");
            assertEvent(events, Watcher.Event.EventType.NodeDeleted, "/a/b/c");
            assertEvent(events, Watcher.Event.EventType.NodeDeleted, "/a/b");
            assertEvent(events, Watcher.Event.EventType.NodeDeleted, "/a");
        }
    }
{code}

I skimmed the code and found two possible causes:
# {{ZKWatchManager.materialize}} materializes all persistent watchers(include 
recursive ones) for {{NodeChildrenChanged}} event.
# {{WatcherModeManager}} trackes only one watcher mode.



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