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From "Michael Han (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2251) Add Client side packet response timeout to avoid infinite wait.
Date Fri, 09 Dec 2016 07:06:58 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15734548#comment-15734548
] 

Michael Han commented on ZOOKEEPER-2251:
----------------------------------------

Has anyone that watching this issue able to have a deterministic reproduce of the issue? The
timeout solution is trivial but it's important to try to figure out root cause of packet loss
otherwise we could just fix the surface and then have unexpected bug bite us. 

> Add Client side packet response timeout to avoid infinite wait.
> ---------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2251
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2251
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: java client
>    Affects Versions: 3.4.9, 3.5.2
>            Reporter: nijel
>            Assignee: Arshad Mohammad
>            Priority: Critical
>              Labels: fault
>             Fix For: 3.4.10, 3.5.3, 3.6.0
>
>         Attachments: ZOOKEEPER-2251-01.patch, ZOOKEEPER-2251-02.patch, ZOOKEEPER-2251-03.patch,
ZOOKEEPER-2251-04.patch
>
>
> I came across one issue related to Client side packet response timeout In my cluster
many packet drops happened for some time.
> One observation is the zookeeper client got hanged. As per the thread dump it is waiting
for the response/ACK for the operation performed (synchronous API used here).
> I am using zookeeper.serverCnxnFactory=org.apache.zookeeper.server.NIOServerCnxnFactory
> Since only few packets missed there is no DISCONNECTED event occurred.
> Need add a "response time out" for the operations or packets.
> *Comments from [~rakeshr]*
> My observation about the problem:-
> * Can use tools like 'Wireshark' to simulate the artificial packet loss.
> * Assume there is only one packet in the 'outgoingQueue' and unfortunately the server
response packet lost. Now, client will enter into infinite waiting. https://github.com/apache/zookeeper/blob/trunk/src/java/main/org/apache/zookeeper/ClientCnxn.java#L1515
> * Probably we can discuss more about this problem and possible solutions(add packet ACK
timeout or another better approach) in the jira.



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