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From "Brian Nixon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-706) large numbers of watches can cause session re-establishment to fail
Date Tue, 28 Aug 2018 21:43:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16595642#comment-16595642

Brian Nixon commented on ZOOKEEPER-706:

I agree that the C client is still vulnerable to this - please do put up a patch if you have
the time.

> 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
>            Assignee: Chris Thunes
>            Priority: Critical
>             Fix For: 3.4.7, 3.5.2, 3.6.0
>         Attachments: ZOOKEEPER-706-branch-34.patch, ZOOKEEPER-706-branch-34.patch, ZOOKEEPER-706.patch,
ZOOKEEPER-706.patch, 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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