[jira] Commented: (ZOOKEEPER-542) c-client can spin when server unresponsive

["Benjamin Reed (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-542?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762683#action_12762683 ] 

Benjamin Reed commented on ZOOKEEPER-542:
-----------------------------------------

+1 good catch and good fix. i'm going to extend the patch slightly by putting in a comment to document how we are handling the non-blocking connect. (somehow that got deleted long ago.)

> c-client can spin when server unresponsive
> ------------------------------------------
>
>                 Key: ZOOKEEPER-542
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-542
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: c client
>    Affects Versions: 3.2.0
>            Reporter: Christian Wiedmann
>         Attachments: ZOOKEEPER-542.patch
>
>
> Due to a mismatch between zookeeper_interest() and zookeeper_process(), when the zookeeper server is unresponsive the client can spin when reconnecting to the server.
> In particular, zookeeper_interest() adds ZOOKEEPER_WRITE whenever there is data to be sent, but flush_send_queue() only writes the data if the state is ZOO_CONNECTED_STATE.  When in ZOO_ASSOCIATING_STATE, this results in spinning.
> This probably doesn't affect production, but I had a runaway process in a development deployment that caused performance issues on the node.  This is easy to reproduce in a single node environment by doing a kill -STOP on the server and waiting for the session timeout.
> Patch to be added.

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