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From "stack (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5270) Handle potential data loss due to concurrent processing of processFaileOver and ServerShutdownHandler
Date Wed, 29 Feb 2012 17:39:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13219354#comment-13219354
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stack commented on HBASE-5270:
------------------------------

@Chunhui You have a new method splitLogIfOnline which will split the log if the server was
online.  Why do you not expire the server? (You remove the expireIfOnline method).

Now we have this initializing state, do you think we should also stop the processing of expired
servers during this startup phase and instead queue them up for processing after the master
is up?  Could do that in another issue maybe since this issue has been going on too long and
your patch is at least an improvement on what we currently have (This startup sequence needs
a big refactor IMO -- it is way too complicated figuring the sequence in which stuff runs).

Are there still holes?  For example, say the .META. server crashes AFTER we've verified it
up in assignRootAndMeta but before we get to do a scan of .META. to rebuild user regions list.
 Could .META. be assigned w/o log splitting finishing?  (I don't think so... .META. would
be offline until the servershutdown handler ran and it would first split logs).

Good stuff.
                
> Handle potential data loss due to concurrent processing of processFaileOver and ServerShutdownHandler
> -----------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5270
>                 URL: https://issues.apache.org/jira/browse/HBASE-5270
>             Project: HBase
>          Issue Type: Sub-task
>          Components: master
>            Reporter: Zhihong Yu
>            Assignee: chunhui shen
>             Fix For: 0.92.1, 0.94.0
>
>         Attachments: 5270-90-testcase.patch, 5270-90-testcasev2.patch, 5270-90.patch,
5270-90v2.patch, 5270-90v3.patch, 5270-testcase.patch, 5270-testcasev2.patch, hbase-5270.patch,
hbase-5270v2.patch, hbase-5270v4.patch, hbase-5270v5.patch, hbase-5270v6.patch, hbase-5270v7.patch,
hbase-5270v8.patch, sampletest.txt
>
>
> This JIRA continues the effort from HBASE-5179. Starting with Stack's comments about
patches for 0.92 and TRUNK:
> Reviewing 0.92v17
> isDeadServerInProgress is a new public method in ServerManager but it does not seem to
be used anywhere.
> Does isDeadRootServerInProgress need to be public? Ditto for meta version.
> This method param names are not right 'definitiveRootServer'; what is meant by definitive?
Do they need this qualifier?
> Is there anything in place to stop us expiring a server twice if its carrying root and
meta?
> What is difference between asking assignment manager isCarryingRoot and this variable
that is passed in? Should be doc'd at least. Ditto for meta.
> I think I've asked for this a few times - onlineServers needs to be explained... either
in javadoc or in comment. This is the param passed into joinCluster. How does it arise? I
think I know but am unsure. God love the poor noob that comes awandering this code trying
to make sense of it all.
> It looks like we get the list by trawling zk for regionserver znodes that have not checked
in. Don't we do this operation earlier in master setup? Are we doing it again here?
> Though distributed split log is configured, we will do in master single process splitting
under some conditions with this patch. Its not explained in code why we would do this. Why
do we think master log splitting 'high priority' when it could very well be slower. Should
we only go this route if distributed splitting is not going on. Do we know if concurrent distributed
log splitting and master splitting works?
> Why would we have dead servers in progress here in master startup? Because a servershutdownhandler
fired?
> This patch is different to the patch for 0.90. Should go into trunk first with tests,
then 0.92. Should it be in this issue? This issue is really hard to follow now. Maybe this
issue is for 0.90.x and new issue for more work on this trunk patch?
> This patch needs to have the v18 differences applied.

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