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From "Jordan Zimmerman (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 Mon, 27 Apr 2015 21:06:38 GMT

    [ https://issues.apache.org/jira/browse/CURATOR-164?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14514999#comment-14514999
] 

Jordan Zimmerman commented on CURATOR-164:
------------------------------------------

* There are lots of classes named Entry. So, I disagree

* "Should updateService be throwing an Exception" - I thought about that too. In the old implementation,
you'd get a KeeperException.NoNode when setData() was called. In the new implementation, we
need to get the Entry instance in order to get the service. So, this seems like a reasonable
change.

* "internalUnregisterService, that looks almost like a double-checked locking" - but it's
not. Just making sure we don't get an NPE.


> 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
>            Assignee: Jordan Zimmerman
>            Priority: Critical
>             Fix For: 2.8.0
>
>
> 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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