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https://issues.apache.org/jira/browse/HBASE-23349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17013344#comment-17013344
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Viraj Jasani commented on HBASE-23349:
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I agree on considering removal of refCount system based on your suggestions
[~apurtell] [~larsh]
However, I am just trying to give one chance to consider both points:
# Perf improvement as part of HBASE-13082
# Scanner reset during compaction if required(config based)
Tried to use volatile enum(NONE, FLUSH, COMPACTION) instead of 2 volatile
booleans for Scanner.next(), seek() calls to not let perf degrade for normal
scans. Hence, if archival is not happening correctly, we can notify open
scanners and reset KV Heap in the next(), seek() runs. However, whether next()
has to reset KVHeap is something that can be determined based on volatile enum
value which would be set while notifying scanners.
[https://github.com/apache/hbase/pull/939] with some tests for Scanner reset
during compaction and successful archival thereafter.
Considering refCount presence in HBase for some time, someone might have
started building some system(alert, recovery etc) based on refCount usecase. In
fact, we have also done auto region reopen etc but other users might have built
some other usecases too.
> Low refCount preventing archival of compacted away files
> --------------------------------------------------------
>
> Key: HBASE-23349
> URL: https://issues.apache.org/jira/browse/HBASE-23349
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 3.0.0, 2.3.0, 1.6.0
> Reporter: Viraj Jasani
> Assignee: Viraj Jasani
> Priority: Major
> Fix For: 3.0.0, 2.3.0, 1.6.0
>
>
> We have observed that refCount on compacted away store files as low as 1 is
> prevent archival.
> {code:java}
> regionserver.HStore - Can't archive compacted file
> hdfs://{{root-dir}}/hbase/data/default/t1/12a9e1112e0371955b3db8d3ebb2d298/cf1/73b72f5ddfce4a34a9e01afe7b83c1f9
> because of either isCompactedAway=true or file has reference,
> isReferencedInReads=true, refCount=1, skipping for now.
> {code}
> We should come up with core code (run as part of discharger thread)
> gracefully resolve reader lock issue by resetting ongoing scanners to start
> pointing to new store files instead of compacted away store files.
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