[jira] [Commented] (HBASE-8729) distributedLogReplay may hang during chained region server failure

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

    [ https://issues.apache.org/jira/browse/HBASE-8729?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13698628#comment-13698628 ] 

stack commented on HBASE-8729:
------------------------------

So we do the below:
{code}
+    boolean needReleaseLock = false;
+    if (!this.services.isInitialized()) {
+      // during master initialization, we could have multiple places splitting a same wal
+      this.splitLogLock.lock();
+      needReleaseLock = true;
...
{code}

rather than ask if lock is 'locked' and unlock it if current thread matches the lock 'owner'?

It is a little odd that the SSH adds a new executor.  I suppose SSH puts itself back on the executor queue if not read to proceed so maybe this ok.

I would be +1 on commit.
                
> 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, hbase-8729-v4.patch, hbase-8729-v5.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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