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https://issues.apache.org/jira/browse/HELIX-124?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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dafu resolved HELIX-124.
------------------------
Resolution: Fixed
Assignee: dafu
fixed in the new HelixManager impl (ParticipantManager, ControllerManager, and
DistributedControllerManager)
> race condition in ZkHelixManager.handleNewSession()
> ---------------------------------------------------
>
> Key: HELIX-124
> URL: https://issues.apache.org/jira/browse/HELIX-124
> Project: Apache Helix
> Issue Type: Sub-task
> Reporter: dafu
> Assignee: dafu
>
> ZkHelixManager.handleNewSession() is an async callback. There is a race
> condition when we have multiple consecutive session expiries. for example:
> 1) sessionExpiry_0 happens, and newSessionId is sessionId_1
> 2) sessionExpiry_1 happens, and newSessionId is sessionId_2
> 3) handleNewSession caused by sessionExpiry_0 is invoked
> 4) handleNewSession caused by sessionExpiry_1 is invoked
> Since 3) and 4) both happen after 2), we will get zk handleNewSession
> callback twice with the same session id (sessionId_2)
> This is problematic:
> if the manager is a PARTICIPANT, the second handleNewSession() will fail to
> create live-instance and reset all listeners. then we come to the situation
> where live-instance exists but no listener is registered for the PARTICIPANT
> if the manager is a CONTROLLER, we add listeners twice
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