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https://issues.apache.org/jira/browse/HBASE-4774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13148742#comment-13148742
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Todd Lipcon commented on HBASE-4774:
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I agree. I also would really like to define a proper FSM class for region state
transitions -- one for RegionOnMaster and another for RegionOnRS (the state
machines are a bit different between the two). The inputs into the state
machines would be ZK state changes as well as lifecycle events in the server.
I've done a bit of hacking in this direction, but it's not a simple project.
> Retain znodes for all regions in UNASSIGNED (zookeeper)
> -------------------------------------------------------
>
> Key: HBASE-4774
> URL: https://issues.apache.org/jira/browse/HBASE-4774
> Project: HBase
> Issue Type: Brainstorming
> Components: master
> Reporter: Karthik Ranganathan
>
> We delete znodes from UNASSIGNED once a region is opened and the open is
> entered into META.
> A lot of multiple assignment issues arise from the fact that we delete this
> znode and dont have state information after the region is opened. So one
> proposal is to always retain the znodes in META and never delete the regions
> from UNASSIGNED. That way we can have a simple, deterministic state machine
> for each region. We could bucket the regions into sub-directories using a
> deterministic hash or the region prefixes.
> Note that what we put in zk is not permanent state but just the state of the
> cluster that is running. This state is invalid upon cluster restart - so we
> are still storing temporary data in zk.
> Thoughts?
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