[jira] [Updated] (ZOOKEEPER-1676) C client zookeeper_interest returning ZOK on Connection Loss

["Yunong Xiao (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-1676?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yunong Xiao updated ZOOKEEPER-1676:
-----------------------------------

    Component/s: c client
    
> C client zookeeper_interest returning ZOK on Connection Loss
> ------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1676
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1676
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: c client
>    Affects Versions: 3.4.3
>         Environment: All
>            Reporter: Yunong Xiao
>            Priority: Critical
>
> I have a fairly simple single-threaded C client set up -- single-threaded
> because we are embedding zk in the node.js/libuv runtime -- which consists of
> the following algorithm:
> zookeeper_interest(); select();
> // perform zookeeper api calls
> zookeeper_process();
> I've noticed that zookeeper_interest in the C client never returns error if it
> is unable to connect to the zk server.
> From the spec of the zookeeper_interest API, I see that zookeeper_interest is
> supposed to return ZCONNECTIONLOSS when disconnected from the client. However,
> digging into the code, I see that the client is making a non-blocking connect
> call
> https://github.com/apache/zookeeper/blob/trunk/src/c/src/zookeeper.c#L1596-1613
> ,  and returning ZOK
> https://github.com/apache/zookeeper/blob/trunk/src/c/src/zookeeper.c#L1684
> If we assume that the server is not up, this will mean that the subsequent
> select() call would return 0, since the fd is not ready, and future calls to
> zookeeper_interest will always return 0 and not the expected ZCONNECTIONLOSS.
> Thus an upstream client will never be aware that the connection is lost.
> I don't think this is the expected behavior. I have temporarily patched the zk
> C client such that zookeeper_interest will return ZCONNECTIONLOSS if it's still
> unable to connect after session_timeout has been exceeded. 
> I have included a patch for the client which fixes this for release 3.4.3 6b35e96 in this branch: https://github.com/yunong/zookeeper/tree/release-3.4.3-patched Here's the patch https://gist.github.com/yunong/efe869a0345867d54adf
> For more information, please see this email thread. http://mail-archives.apache.org/mod_mbox/zookeeper-dev/201211.mbox/%3C11A8E7C3-4DDE-45D8-ABEC-A8A4D32CF647@gmail.com%3E

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