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From "Jeffrey Zhong (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7824) Improve master start up time when there is log splitting work
Date Sun, 07 Apr 2013 02:41:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13624596#comment-13624596

Jeffrey Zhong commented on HBASE-7824:

Let me add more clarifications to your first comments to see if you agree firstly:

If the META RS(it is also the ROOT RS) is dead between step2 and step3, MetaSSH start splitting
its hlog.
The root recovery portion in Meta SSH will complete log splitting for both ROOT and META regions.
Therefore, all recovered edits files are created before Meta region can be assigned because
meta region can only be assigned only when ROOT is online. By then, all recovered edits files
are created and they will be replayed when meta region is opened during assignment.

However step3 will assign META directly(Because HMaster#splitLogAndExpireIfOnline will return
null), it means META will loss the data from hlog.
This is all right because the existing log splitting work has already be done and will be
replayed during META region open phase.

Thanks for your feedbacks.

> Improve master start up time when there is log splitting work
> -------------------------------------------------------------
>                 Key: HBASE-7824
>                 URL: https://issues.apache.org/jira/browse/HBASE-7824
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>            Reporter: Jeffrey Zhong
>            Assignee: Jeffrey Zhong
>             Fix For: 0.94.8
>         Attachments: hbase-7824.patch, hbase-7824_v2.patch, hbase-7824_v3.patch, hbase-7824-v7.patch,
> When there is log split work going on, master start up waits till all log split work
completes even though the log split has nothing to do with meta region servers.
> It's a bad behavior considering a master node can run when log split is happening while
its start up is blocking by log split work. 
> Since master is kind of single point of failure, we should start it ASAP.

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