[jira] [Commented] (HBASE-21035) Meta Table should be able to online even if all procedures are lost

["Allan Yang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-21035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16671049#comment-16671049 ] 

Allan Yang commented on HBASE-21035:
------------------------------------

The problem mentioned in this issue need to be discussed again. 
I tried to update a 1.x cluster to 2.x. Firstly, I stopped all servers(may leave some splitting wal dirs). Then I started 2.x in place, but since now when master starting,  we totally count on the procedures, and won't care about the splitting WAL dirs, some data may loss. And there is no SCPs to bring meta online.
This would be a problem for people who want to upgrade their clusters from 1.x to 2.x. [~stack],[~Apache9]

> Meta Table should be able to online even if all procedures are lost
> -------------------------------------------------------------------
>
>                 Key: HBASE-21035
>                 URL: https://issues.apache.org/jira/browse/HBASE-21035
>             Project: HBase
>          Issue Type: Sub-task
>    Affects Versions: 2.1.0
>            Reporter: Allan Yang
>            Assignee: Allan Yang
>            Priority: Major
>         Attachments: HBASE-21035.branch-2.0.001.patch, HBASE-21035.branch-2.1.001.patch
>
>
> After HBASE-20708, we changed the way we init after master starts. It will only check WAL dirs and compare to Zookeeper RS nodes to decide which server need to expire. For servers which's dir is ending with 'SPLITTING', we assure that there will be a SCP for it.
> But, if the server with the meta region crashed before master restarts, and if all the procedure wals are lost (due to bug, or deleted manually, whatever), the new restarted master will be stuck when initing. Since no one will bring meta region online.
> Although it is an anomaly case, but I think no matter what happens, we need to online meta region. Otherwise, we are sitting ducks, noting can be done.



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