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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5875) Process RIT and Master restart may remove an online server considering it as a dead server
Date Thu, 03 May 2012 05:48:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267209#comment-13267209
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stack commented on HBASE-5875:
------------------------------

The patch looks dodgy -- saying a region is online, if it is root or meta, seems incorrect.

bq. Consider the case where my ROOT node is found in RIT. Hence the processRIT will trigger
the assignment.

What is the above referring to?  Which part of the code?

bq. It so happened that when i try to verifyRootRegionLocation the root node is created but
the OpenRegionHandler has not added the ROOT region in its memory(very very corner case and
this happened once while testing). So the verifyRootRegionLocation returns false and hence
the master thinks it an server to be expired. 

Can the master not detect this corner case just by looking at whats in zk?


                
> Process RIT and Master restart may remove an online server considering it as a dead server
> ------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5875
>                 URL: https://issues.apache.org/jira/browse/HBASE-5875
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.1
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.94.1
>
>         Attachments: HBASE-5875.patch
>
>
> If on master restart it finds the ROOT/META to be in RIT state, master tries to assign
the ROOT region through ProcessRIT.
> Master will trigger the assignment and next will try to verify the Root Region Location.
> Root region location verification is done seeing if the RS has the region in its online
list.
> If the master triggered assignment has not yet been completed in RS then the verify root
region location will fail.
> Because it failed 
> {code}
> splitLogAndExpireIfOnline(currentRootServer);
> {code}
> we do split log and also remove the server from online server list. Ideally here there
is nothing to do in splitlog as no region server was restarted.
> So master, though the server is online, master just invalidates the region server.
> In a special case, if i have only one RS then my cluster will become non operative.

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