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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CURATOR-164) curator-x-discovery: unregisterService is not guaranteed to remove the service, due to reconnectListener concurrency issue
Date Fri, 10 Apr 2015 04:38:12 GMT

    [ https://issues.apache.org/jira/browse/CURATOR-164?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14488888#comment-14488888
] 

Mike Drob commented on CURATOR-164:
-----------------------------------

Here's a potential thread sequencing on the race condition:

{noformat}
        // T1: unregisterService()
        // T2: connectionStateListener.stateChanged()
        // T2: reRegisterServices()
        // T2: internalRegisterService(x)
        // T1: client.delete(path(x))
        // T1: services.remove(x)
        // T2: client.create(path(x))
{noformat}

Pull request incoming.

> curator-x-discovery: unregisterService is not guaranteed to remove the service, due to
reconnectListener concurrency issue
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CURATOR-164
>                 URL: https://issues.apache.org/jira/browse/CURATOR-164
>             Project: Apache Curator
>          Issue Type: Bug
>          Components: Framework
>    Affects Versions: 2.7.0
>            Reporter: Rasmus Berg Palm
>            Priority: Critical
>
> In ServiceDiscoveryImpl:
> When unregistering a service, the reconnect listener might fire while deleting the path.
> This can cause a condition where the delete finishes successfully, the service is removed
from services, and then the reRegisterServices completes successfully and the service is added
back in ZK and in services, end result being that the service was not removed, even though
unregisterService did not throw any exceptions. 
> Essentially the use of the internal 'services' cache makes for a nightmare of concurrency
issues. I put this as critical as the library it's really not usable IMO.



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