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https://issues.apache.org/jira/browse/HBASE-23181?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16960662#comment-16960662
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Michael Stack commented on HBASE-23181:
---------------------------------------

Ran cluster test with heavy load overrunning hbase against branch-2.2 (i.e. w/ 
this patch). This problem did not show (Plenty of others did but that is 
another story). Will run more but looking good.

> Blocked WAL archive: "LogRoller: Failed to schedule flush of XXXX, because it 
> is not online on us"
> --------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-23181
>                 URL: https://issues.apache.org/jira/browse/HBASE-23181
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver, wal
>    Affects Versions: 2.2.1
>            Reporter: Michael Stack
>            Assignee: Duo Zhang
>            Priority: Major
>             Fix For: 3.0.0, 2.3.0, 2.1.8, 2.2.3
>
>
> On a heavily loaded cluster, WAL count keeps rising and we can get into a 
> state where we are not rolling the logs off fast enough. In particular, there 
> is this interesting state at the extreme where we pick a region to flush 
> because 'Too many WALs' but the region is actually not online. As the WAL 
> count rises, we keep picking a region-to-flush that is no longer on the 
> server. This condition blocks our being able to clear WALs; eventually WALs 
> climb into the hundreds and the RS goes zombie with a full Call queue that 
> starts throwing CallQueueTooLargeExceptions (bad if this servers is the one 
> carrying hbase:meta): i.e. clients fail to access the RegionServer.
> One symptom is a fast spike in WAL count for the RS. A restart of the RS will 
> break the bind.
> Here is how it looks in the log:
> {code}
> # Here is region closing....
> 2019-10-16 23:10:55,897 INFO 
> org.apache.hadoop.hbase.regionserver.handler.UnassignRegionHandler: Closed 
> 8ee433ad59526778c53cc85ed3762d0b
> ....
> # Then soon after ...
> 2019-10-16 23:11:44,041 WARN org.apache.hadoop.hbase.regionserver.LogRoller: 
> Failed to schedule flush of 8ee433ad59526778c53cc85ed3762d0b, because it is 
> not online on us
> 2019-10-16 23:11:45,006 INFO 
> org.apache.hadoop.hbase.regionserver.wal.AbstractFSWAL: Too many WALs; 
> count=45, max=32; forcing flush of 1 regions(s): 
> 8ee433ad59526778c53cc85ed3762d0b
> ...
> # Later...
> 2019-10-16 23:20:25,427 INFO 
> org.apache.hadoop.hbase.regionserver.wal.AbstractFSWAL: Too many WALs; 
> count=542, max=32; forcing flush of 1 regions(s): 
> 8ee433ad59526778c53cc85ed3762d0b
> 2019-10-16 23:20:25,427 WARN org.apache.hadoop.hbase.regionserver.LogRoller: 
> Failed to schedule flush of 8ee433ad59526778c53cc85ed3762d0b, because it is 
> not online on us
> {code}
> I've seen this runaway WALs 2.2.1. I've seen runaway WALs in a 1.2.x version 
> regularly that had HBASE-16721 fix in it, but can't say yet if it was for 
> same reason as above.



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