[I] [Bug] Concurrent ZK notification cleanup throws NoSuchElementException [fluss]

["gyang94 (via GitHub)" <gi...@apache.org>]

gyang94 opened a new issue, #3753:
URL: https://github.com/apache/fluss/issues/3753

   ### Search before asking
   
   - [x] I searched in the [issues](https://github.com/apache/fluss/issues) and found nothing similar.
   
   
   ### Fluss version
   
   0.9.0 (latest release)
   
   ### Please describe the bug 🐞
   
   #### Description
   
   In a multi-server cluster, updating dynamic configs may produce the following error after the configs have been applied successfully:
   
   ```text
   ERROR ZkNodeChangeNotificationWatcher - Error while purging obsolete notification change for path = /config/changes/config_change_0000000007
   java.util.NoSuchElementException: No value present
       at java.util.Optional.get(Optional.java:143)
       at org.apache.fluss.server.authorizer.ZkNodeChangeNotificationWatcher.purgeObsoleteNotifications(ZkNodeChangeNotificationWatcher.java:142)
   ```
   
   <img width="832" height="145" alt="Image" src="https://github.com/user-attachments/assets/65c77bdb-9645-484b-a747-1f72c252a373" />
   
   #### Root cause
   Each watcher reads a snapshot of all children under /config/changes and independently purges expired nodes. After one watcher deletes a node, another watcher may still have it in its children snapshot.
   getStat() then returns Optional.empty(), but the result is accessed directly with Optional.get():
   ```
   Stat state = zooKeeperClient.getStat(notificationNode).get();
   ```
   
   ### Solution
   
   Do empty check before get the state.
   
   
   
   ### Are you willing to submit a PR?
   
   - [x] I'm willing to submit a PR!


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Re: [I] [Bug] Concurrent ZK notification cleanup throws NoSuchElementException [fluss]

["fresh-borzoni (via GitHub)" <gi...@apache.org>]

fresh-borzoni closed issue #3753: [Bug] Concurrent ZK notification cleanup throws NoSuchElementException
URL: https://github.com/apache/fluss/issues/3753


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