[Bug] Kyuubi Fails to Rearm the Engine Deregistration Watcher After ZooKeeper Reconnect

[Yangxuhao123]

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Describe the bug

When a Kyuubi engine’s ZooKeeper session expires and reconnects, its deregistration watcher is not rearmed on the restored discovery node. As a result, deleting the node may fail to trigger graceful shutdown, allowing an unhealthy engine to remain discoverable and continue accepting new sessions.

Affects Version(s)

master

Kyuubi Server Log Output

Kyuubi Engine Log Output

  26/07/08 11:32:54 WARN ClientCnxn: Client session timed out ... sessionid 0x110dd5e23c59e86
  26/07/08 11:33:52 WARN ClientCnxn: Client session timed out ... sessionid 0x309721e0b579613
  26/07/08 11:33:52 INFO ClientCnxn: ... closing socket connection and attempting reconnect
  26/07/08 11:33:52 INFO ZookeeperDiscoveryClient: Zookeeper client connection state changed to: SUSPENDED

  26/07/08 11:33:53 WARN ClientCnxn: ... session 0x309721e0b579613 has expired
  26/07/08 11:33:53 INFO ZookeeperDiscoveryClient: Zookeeper client connection state changed to: LOST
  26/07/08 11:33:53 WARN ConnectionState: Session expired event received
  26/07/08 11:33:53 INFO ZookeeperDiscoveryClient: Zookeeper client connection state changed to: RECONNECTED

  26/07/08 11:33:53 WARN ClientCnxn: ... session 0x110dd5e23c59e86 has expired
  26/07/08 11:33:53 INFO ZookeeperDiscoveryClient: Zookeeper client connection state changed to: LOST
  26/07/08 11:33:53 WARN ConnectionState: Session expired event received
  26/07/08 11:33:53 INFO ZookeeperDiscoveryClient: Zookeeper client connection state changed to: RECONNECTED

Kyuubi Server Configurations

Kyuubi Engine Configurations

Additional context

No response

Are you willing to submit PR?

• Yes. I would be willing to submit a PR with guidance from the Kyuubi community to fix.
• No. I cannot submit a PR at this time.

[github-actions]

Hello @Yangxuhao123,
Thanks for finding the time to report the issue!
We really appreciate the community's efforts to improve Apache Kyuubi.