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https://issues.apache.org/jira/browse/HBASE-22072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16821670#comment-16821670
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ramkrishna.s.vasudevan commented on HBASE-22072:
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bq.But the scanner is still not over. And so the scanner did not get a chance
to update the readers. So we can not really do this immediate return model.
This is what I tried to check in the code. As per my code reading it seems once
a StoreScanner says close(false) in the next() flow or reseek() flow it means
from the region level there are not going to be any other scan that is going to
happen from that StoreScanner. Finally after a shipped call this store scanner
will be closed when the scan completes. So I felt it is better we just don't
update the readers in that case. And that is why if at all there is a close()
call we just avoid the updateReaders itself. The other way to look at that is
by making 'closing' true in all cases.
> High read/write intensive regions may cause long crash recovery
> ---------------------------------------------------------------
>
> Key: HBASE-22072
> URL: https://issues.apache.org/jira/browse/HBASE-22072
> Project: HBase
> Issue Type: Bug
> Components: Performance, Recovery
> Affects Versions: 2.1.2
> Reporter: Pavel
> Assignee: ramkrishna.s.vasudevan
> Priority: Major
> Attachments: HBASE-22072.HBASE-21879-v1.patch
>
>
> Compaction of high read loaded region may leave compacted files undeleted
> because of existing scan references:
> INFO org.apache.hadoop.hbase.regionserver.HStore - Can't archive compacted
> file hdfs://hdfs-ha/hbase... because of either isCompactedAway=true or file
> has reference, isReferencedInReads=true, refCount=1, skipping for now
> If region is either high write loaded this happens quite often and region may
> have few storefiles and tons of undeleted compacted hdfs files.
> Region keeps all that files (in my case thousands) untill graceful region
> closing procedure, which ignores existing references and drop obsolete files.
> It works fine unless consuming some extra hdfs space, but only in case of
> normal region closing. If region server crashes than new region server,
> responsible for that overfiling region, reads hdfs folder and try to deal
> with all undeleted files, producing tons of storefiles, compaction tasks and
> consuming abnormal amount of memory, wich may lead to OutOfMemory Exception
> and further region servers crash. This stops writing to region because number
> of storefiles reach *hbase.hstore.blockingStoreFiles* limit, forces high GC
> duty and may take hours to compact all files into working set of files.
> Workaround is a periodically check hdfs folders files count and force region
> assign for ones with too many files.
> It could be nice if regionserver had a setting similar to
> hbase.hstore.blockingStoreFiles and invoke attempt to drop undeleted
> compacted files if number of files reaches this setting.
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