[jira] [Commented] (ZOOKEEPER-706) large numbers of watches can cause session re-establishment to fail

["Raul Gutierrez Segales (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14583843#comment-14583843 ] 

Raul Gutierrez Segales commented on ZOOKEEPER-706:
--------------------------------------------------

lgtm, +1.

Thanks for the patch [~cthunes]! Do you think you could add a test? I think we could go without one, but given the assumption has always been there's only one SetWatches() packet after reconnect, it might be good to have a small test for this. 

> large numbers of watches can cause session re-establishment to fail
> -------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-706
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-706
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: c client, java client
>    Affects Versions: 3.1.2, 3.2.2, 3.3.0
>            Reporter: Patrick Hunt
>            Priority: Critical
>             Fix For: 3.4.7, 3.5.2, 3.6.0
>
>         Attachments: ZOOKEEPER-706.patch
>
>
> If a client sets a large number of watches the "set watches" operation during session re-establishment can fail.
> for example:
>  WARN  [NIOServerCxn.Factory:22801:NIOServerCnxn@417] - Exception causing close of session 0xe727001201a4ee7c due to java.io.IOException: Len error 4348380
> in this case the client was a web monitoring app and had set both data and child watches on > 32k znodes.
> there are two issues I see here we need to fix:
> 1) handle this case properly (split up the set watches into multiple calls I guess...)
> 2) the session should have expired after the "timeout". however we seem to consider any message from the client as re-setting the expiration on the server side. Probably we should only consider messages from the client that are sent during an established session, otherwise we can see this situation where the session is not established however the session is not expired either. Perhaps we should create another JIRA for this particular issue.



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