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From "Liyin Tang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3065) Retry all 'retryable' zk operations; e.g. connection loss
Date Sat, 02 Apr 2011 00:01:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13014889#comment-13014889
] 

Liyin Tang commented on HBASE-3065:
-----------------------------------

Changing the zk data format has a compatible problem.
Right now, I put some MAGIC number at the beginning of the new format zk data. 
So it can handle the old format zk data easily.
 
But the origin code cannot handle the new format of zk data. 
When deploying, it needs a fresh restart and deploy all the new jar files together.


> Retry all 'retryable' zk operations; e.g. connection loss
> ---------------------------------------------------------
>
>                 Key: HBASE-3065
>                 URL: https://issues.apache.org/jira/browse/HBASE-3065
>             Project: HBase
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: Liyin Tang
>             Fix For: 0.92.0
>
>
> The 'new' master refactored our zk code tidying up all zk accesses and coralling them
behind nice zk utility classes.  One improvement was letting out all KeeperExceptions letting
the client deal.  Thats good generally because in old days, we'd suppress important state
zk changes in state.  But there is at least one case the new zk utility could handle for the
application and thats the class of retryable KeeperExceptions.  The one that comes to mind
is conection loss.  On connection loss we should retry the just-failed operation.  Usually
the retry will just work.  At worse, on reconnect, we'll pick up the expired session event.

> Adding in this change shouldn't be too bad given the refactor of zk corralled all zk
access into one or two classes only.
> One thing to consider though is how much we should retry.  We could retry on a timer
or we could retry for ever as long as the Stoppable interface is passed so if another thread
has stopped or aborted the hosting service, we'll notice and give up trying.  Doing the latter
is probably better than some kinda timeout.
> HBASE-3062 adds a timed retry on the first zk operation.  This issue is about generalizing
what is over there across all zk access.

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