[jira] Commented: (ZOOKEEPER-417) stray message problem when changing servers

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-417?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723483#action_12723483 ] 

Hadoop QA commented on ZOOKEEPER-417:
-------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12411594/ZOOKEEPER-417.patch
  against trunk revision 787907.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 12 new or modified tests.

    -1 patch.  The patch command could not apply the patch.

Console output: http://hudson.zones.apache.org/hudson/job/Zookeeper-Patch-vesta.apache.org/130/console

This message is automatically generated.

> stray message problem when changing servers
> -------------------------------------------
>
>                 Key: ZOOKEEPER-417
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-417
>             Project: Zookeeper
>          Issue Type: Bug
>            Reporter: Benjamin Reed
>            Assignee: Benjamin Reed
>            Priority: Blocker
>             Fix For: 3.2.0
>
>         Attachments: ZOOKEEPER-417.patch
>
>
> There is  a possibility for stray messages from a previous connection to violate ordering and generally cause problems. Here is a scenario: we have a client, C, two followers, F1 and F2, and a leader, L. The client is connected to F1, which is a slow follower. C sends setData("/a", "1") to F1 and then loses the connection, so C reconnects to F2 and sends setData("/a", "2").  it is possible, if F1 is slow enough and the setData("/a", "1") got onto the network before the connection break, for F1 to forward the setData("/a", "1") to L after F2 forwards setData("/a", "2").
> to fix this, the leader should keep track of which follower last registered a session for a client and drop any requests from followers for clients for whom they do not have a registration. 

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