[jira] [Updated] (HBASE-4060) Making region assignment more robust

["Ted Yu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-4060?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ted Yu updated HBASE-4060:
--------------------------

    Assignee:     (was: Ted Yu)

> Making region assignment more robust
> ------------------------------------
>
>                 Key: HBASE-4060
>                 URL: https://issues.apache.org/jira/browse/HBASE-4060
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.3
>            Reporter: Ted Yu
>
> From Eran Kutner:
> My concern is that the region allocation process seems to rely too much on
> timing considerations and doesn't seem to take enough measures to guarantee
> conflicts do not occur. I understand that in a distributed environment, when
> you don't get a timely response from a remote machine you can't know for
> sure if it did or did not receive the request, however there are things that
> can be done to mitigate this and reduce the conflict time significantly. For
> example, when I run dbck it knows that some regions are multiply assigned,
> the master could do the same and try to resolve the conflict. Another
> approach would be to handle late responses, even if the response from the
> remote machine arrives after it was assumed to be dead the master should
> have enough information to know it had created a conflict by assigning the
> region to another server. An even better solution, I think, is for the RS to
> periodically test that it is indeed the rightful owner of every region it
> holds and relinquish control over the region if it's not.
> Obviously a state where two RSs hold the same region is pathological and can
> lead to data loss, as demonstrated in my case. The system should be able to
> actively protect itself against such a scenario. It probably doesn't need
> saying but there is really nothing worse for a data storage system than data
> loss.
> In my case the problem didn't happen in the initial phase but after
> disabling and enabling a table with about 12K regions.

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