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https://issues.apache.org/jira/browse/ZOOKEEPER-706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14584051#comment-14584051
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Raul Gutierrez Segales commented on ZOOKEEPER-706:
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So chatting with [~svoutil] about this, we think there is an issue in:
{code}
+ SetWatches sw = new SetWatches(lastZxid,
+ dataWatchesBatch,
+ existWatchesBatch,
+ childWatchesBatch);
{code}
The lastZxid should be the *same* for all SetWatches packets. Given it can
change while you are looping (because a watch could have fired, and triggered a
read), that would cause the client to claim that it's further ahead than it
really is.
So we should save lastZxid before we start sending the SetWatches packets.
> 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-branch-34.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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