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https://issues.apache.org/jira/browse/ZOOKEEPER-4466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17495772#comment-17495772
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Enrico Olivelli commented on ZOOKEEPER-4466:
--------------------------------------------
So basically you say that if you set a persistent watch we are missing to send
notifications to regular watches?
In this case if we implement the expected behaviour then we are not breaking
compatibility (we will be sending more notifications, not fewer)
> 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
> Assignee: Kezhu Wang
> Priority: Major
>
> 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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