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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5682) Allow HConnectionImplementation to recover from ZK connection loss (for 0.94 only)
Date Sat, 31 Mar 2012 22:48:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13243589#comment-13243589
] 

Lars Hofhansl commented on HBASE-5682:
--------------------------------------

"perversion" is hard word. :) It is just rechecking before each use whether the trackers are
still usable. The timeout is handled through the HConnection's abort().

The testing I've done:
# ZK down, HBase down, start a client. Then start ZK, then HBase.
# ZK up, HBase down, start client. Then start HBase
# both ZK and HBase up, start client, kill HBase, restart HBase
# both ZK and HBase up, start client, kill ZK and HBase restart

The client just create a new HTable and then tries to get some rows in a loop.
In all cases the client should successfully be able to reconnect when both ZK and HBase are
up.

The problem I have seen in 0.94/0.92 without this patch even with managed connections is that
after HConnection times out, it is unusable and even getting a new HTable does not fix the
problem since behind the scenes the same HConnection is retrieved.

Will think about an automated test. Do you like the version better that always does the recheck
(and hence all the conditional for "managed" go away)?

                
> Allow HConnectionImplementation to recover from ZK connection loss (for 0.94 only)
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-5682
>                 URL: https://issues.apache.org/jira/browse/HBASE-5682
>             Project: HBase
>          Issue Type: Improvement
>          Components: client
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.0
>
>         Attachments: 5682-all.txt, 5682-v2.txt, 5682.txt
>
>
> Just realized that without this HBASE-4805 is broken.
> I.e. there's no point keeping a persistent HConnection around if it can be rendered permanently
unusable if the ZK connection is lost temporarily.
> Note that this is fixed in 0.96 with HBASE-5399 (but that seems to big to backport)

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