[jira] Commented: (ZOOKEEPER-922) enable faster timeout of sessions in case of unexpected socket disconnect

["Benjamin Reed (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12929683#action_12929683 ] 

Benjamin Reed commented on ZOOKEEPER-922:
-----------------------------------------

how do you deal with the following race condition:

1) the client is connected to follower1
2) the client has problems talking to follower1, so it closes the connection
3) the client connects to follower2
4) follower1 detects the closed connection and sets the connection timeout to min
5) the client is idle for min timeout and the leader expires the connection

the race condition is steps 3) and 4). if follower1 doesn't detect the dead connection fast enough, it can improperly set the timeout.

> enable faster timeout of sessions in case of unexpected socket disconnect
> -------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-922
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-922
>             Project: Zookeeper
>          Issue Type: Improvement
>          Components: server
>            Reporter: Camille Fournier
>            Assignee: Camille Fournier
>             Fix For: 3.4.0
>
>         Attachments: ZOOKEEPER-922.patch
>
>
> In the case when a client connection is closed due to socket error instead of the client calling close explicitly, it would be nice to enable the session associated with that client to time out faster than the negotiated session timeout. This would enable a zookeeper ensemble that is acting as a dynamic discovery provider to remove ephemeral nodes for crashed clients quickly, while allowing for a longer heartbeat-based timeout for java clients that need to do long stop-the-world GC. 
> I propose doing this by setting the timeout associated with the crashed session to "minSessionTimeout".

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