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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2700) Handle master failover for regions in transition
Date Wed, 23 Jun 2010 17:37:53 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881780#action_12881780
] 

stack commented on HBASE-2700:
------------------------------

Here is the pertinent paragraph from the BT table:

"When a master is started by the cluster management system, it needs to discover the current
tablet assign- ments before it can change them. The master executes the following steps at
startup. (1) The master grabs a unique master lock in Chubby, which prevents con- current
master instantiations. (2) The master scans the servers directory in Chubby to find the live
servers. (3) The master communicates with every live tablet server to discover what tablets
are already assigned to each server. (4) The master scans the METADATA table to learn the
set of tablets. Whenever this scan encounters a tablet that is not already assigned, the master
adds the tablet to the set of unassigned tablets, which makes the tablet eligible for tablet
assignment."

Any reason, we are doing otherwise; e.g. Step 3, it asks the RS what its carrying rather than
ask Chubby and Step 4, scans .META. to learn list of regions rather than scan Chubby?

> Handle master failover for regions in transition
> ------------------------------------------------
>
>                 Key: HBASE-2700
>                 URL: https://issues.apache.org/jira/browse/HBASE-2700
>             Project: HBase
>          Issue Type: Sub-task
>          Components: master, zookeeper
>            Reporter: Jonathan Gray
>            Priority: Critical
>             Fix For: 0.21.0
>
>
> To this point in HBASE-2692 tasks we have moved everything for regions in transition
into ZK, but we have not fully handled the master failover case.  This is to deal with that
and to write tests for it.

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