[ZOOKEEPER-4471] Remove WatcherType.Children break persistent watcher's child events

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 3.6.3, 3.7.0
• Fix Version/s: 3.9.0
• Component/s: server
• Labels: pull-request-available

Release Note

Previously, removing WatcherType::Data or WatcherType::Children from AddWatchMode::Persistent will succeed in server side and part of AddWatchMode.PERSISTENT will be left behind. And we get persistent children or data watchers. We are never claiming to support these type of watchers and neither intend to do such "compute" in server side, so we decide to forbid this behavior. Such operation resulted in NOWATCHER in Java client anyway.

• Assignee: Kezhu Wang
• Reporter: Kezhu Wang
• Created: 21/Feb/22 04:05
• Updated: 04/Aug/23 11:28
• Resolved: 13/Jun/23 13:35

Description

AddWatchMode.PERSISTENT was divided as data and child watch in server side. When remove WatcherType.Children, child part of AddWatchMode.PERSISTENT is removed but not its data part. This could introduce trick usage of persistent data watch while there is no official api for this. It is better forbid this by dedicate WatcherType.Children to standard child watch only.

I commits a modified RemoveWatchesTest.testRemoveAllChildWatchesOnAPath in my local repo to reproduce this.

I think it is better to support removeWatches for two persistent watchers too. But it might be a separate issue.

Issue Links

• is related to: ZOOKEEPER-4472 Support persistent watchers removing individually
• links to: GitHub Pull Request #1998