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From "chunhui shen (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5270) Handle potential data loss due to concurrent processing of processFaileOver and ServerShutdownHandler
Date Wed, 25 Jan 2012 03:04:43 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13192828#comment-13192828
] 

chunhui shen commented on HBASE-5270:
-------------------------------------

Thanks for stack's comment
{code}This method param names are not right 'definitiveRootServer'; what is meant by definitive?
 Do they need this qualifier?
{code}
When master is initializing, carryingMeta and carryingRoot is always false (We could see it
from the code of ServerManger#expire()). So, the param 'definitiveRootServer' is used in this
case to ensure the dead root server is carryingRoot when it is being expired.


{code}Is there anything in place to stop us expiring a server twice if its carrying root and
meta?
{code}
Is there any possible to expire a server if its carrying root and meta now? I don't think
so.

{code}onlineServers needs to be explained{code}
I think so, this param is not be passed into joinCluster before, so when executing joinCluster
, the onlineServers  is current online servers. However, it has a problem before, when executing
joinCluster , maybe some server is being processed as dead server, so its log is being splitted
by SSH while its regions are being assigned by joinCluster(),causing data loss.

{code}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?
{code}
I don't find this operation earlier in master setup, and this operation is not introduced
by this issue. And I only introduce this logic for 90 from trunk.

{code}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.{code}
I think we need explain it, But whether we shouldn't use distributed split log, I'm not very
sure.

{code}Why would we have dead servers in progress here in master startup?  Because a servershutdownhandler
fired?
{code}
When matser is initializing, if one RS is killed and  restart, then dead server is in progress
while master startup
                
> 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
>             Fix For: 0.94.0, 0.92.1
>
>
> 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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