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https://issues.apache.org/jira/browse/HBASE-8729?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13680947#comment-13680947
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stack commented on HBASE-8729:
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bq. If we don't introduce the new log replay handler, setting N is tricky and
its value has to be big enough so that we won't end up in issue of the JIRA.
Ok. So SSHs do basic processing and then we queue up all log splitting in the
new set of executors.... SSH can move on to next server and queue up more log
splitting but won't get blocked.
+1 then.
> distributedLogReplay may hang during chained region server failure
> ------------------------------------------------------------------
>
> Key: HBASE-8729
> URL: https://issues.apache.org/jira/browse/HBASE-8729
> Project: HBase
> Issue Type: Bug
> Components: MTTR
> Reporter: Jeffrey Zhong
> Assignee: Jeffrey Zhong
> Fix For: 0.98.0, 0.95.2
>
> Attachments: 8729-v2.patch, hbase-8729.patch, hbase-8729-v3.patch
>
>
> In a test, half cluster(in terms of region servers) was down and some log
> replay had incurred chained RS failures(receiving RS of a log replay failed
> again).
> Since by default, we only allow 3 concurrent SSH handlers(controlled by
> {code}this.executorService.startExecutorService(ExecutorType.MASTER_SERVER_OPERATIONS,conf.getInt("hbase.master.executor.serverops.threads",
> 3));{code}).
> If all 3 SSH handlers are doing logReplay(blocking call) and one of receiving
> RS fails again then logReplay will hang because regions of the newly failed
> RS can't be re-assigned to another live RS(no ssh handler will be processed
> due to max threads setting) and existing log replay will keep routing replay
> traffic to the dead RS.
> The fix is to submit logReplay work into a separate type of executor queue in
> order not to block SSH region assignment so that logReplay can route traffic
> to a live RS after retries and move forward.
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