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https://issues.apache.org/jira/browse/HBASE-8545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13662149#comment-13662149
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Jimmy Xiang commented on HBASE-8545:
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This is a very rare racing issue. It really depends how thing happens at that
moment. Since the region plan uses the old server, it means
isDeadServer(serveName) could return false, while the server is already dead
because there is a short time in the middle.
> Meta stuck in transition when it is assigned to a just restarted dead region
> sever
> -----------------------------------------------------------------------------------
>
> Key: HBASE-8545
> URL: https://issues.apache.org/jira/browse/HBASE-8545
> Project: HBase
> Issue Type: Bug
> Components: Region Assignment
> Reporter: Jimmy Xiang
> Assignee: Jimmy Xiang
> Attachments: trunk-8545.patch, trunk-8545_v2.patch
>
>
> Support the meta region server is down, and the SSH tries to re-assign it.
> This could happen:
> 1. AM plans to assign meta to a region server (R_old);
> 2. Now R_old is dead, the new region server (R_new) starts up on the same
> host, port, but gets a different start code;
> 3. AM sends the open region request to R_new and the Meta is opened on it;
> 4. AM gets ZK event, but it is from a different region server instance
> (R_new), not the expected one (R_old), so it sends a close region request to
> R_new;
> 5. Now, the meta is stuck in transition and won't be assigned.
> This won't happen to a user region since the SSH for R_old will find out the
> user region stuck in transition and re-assign it. For meta, it is a little
> different. AM checks if a dead region server carries the meta based on the
> ZK info, which is changed to the new region server R_new at step 3 by the
> open region handler.
> The fix I was thinking about is:
> 1. In checking if a region server carries a region, uses the region
> transition information if it exists (which is the source of truth, to
> master), if not, checks the ZK data as before;
> 2. In open region handler, when transition assign zk node from offline to
> opening, make sure the current region server is the expected one
> (ZK#transitionNode, existing code doesn't check the target server name).
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