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https://issues.apache.org/jira/browse/S4-3?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13127327#comment-13127327
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Flavio Junqueira commented on S4-3:
-----------------------------------
I'm not sure why you say that closing the session would be session would be
difficult to implement. A call to close() the handle would invalidate the
session and delete the ephemerals. I'm more inclined to check if the node
exists and if the client is the owner, though.
Also, apparently I forgot to add the URL to wiki page on error handling in my
last comment: http://wiki.apache.org/hadoop/ZooKeeper/ErrorHandling
> Sometimes one process node owns 2 tasks
> ---------------------------------------
>
> Key: S4-3
> URL: https://issues.apache.org/jira/browse/S4-3
> Project: Apache S4
> Issue Type: Bug
> Reporter: Gavin Li
> Assignee: Gavin Li
> Attachments: s4_loscon_fix
>
>
> When using S4, we found sometimes it ends up with one process node owns 2
> tasks. I did some investigation, it seems that the handling of
> ConnectionLossException when creating the ephemeral node is problematic.
> Sometimes when the response from zookeeper server times out,
> zookeeper.create() will fail with ConnectionLossException while the creation
> request might already be sent to server(see
> http://svn.apache.org/viewvc/hadoop/zookeeper/trunk/src/java/main/org/apache/zookeeper/ClientCnxn.java
> line 830). From our logs this is the case we ran into.
> Maybe we should handle it in the way that HBase is handling it
> (http://svn.apache.org/viewvc/hbase/trunk/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java?view=markup),
> just simply exit the process when got that exception to let the whole
> process restart.
> To be more clear, what happened was: a process node called zookeeper.create()
> to acquire a task, the request was successfully sent to zookeeper server, but
> the zookeeper IO loop timed out before the response came. So the
> zookeeper.create() failed with ConnectionLossException. Then the process node
> ignored this exception and tried to acquire another task. Then it got 2 tasks.
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