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https://issues.apache.org/jira/browse/HBASE-20430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nihal Jain updated HBASE-20430:
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Labels: s3 (was: )
> Improve store file management for non-HDFS filesystems
> ------------------------------------------------------
>
> Key: HBASE-20430
> URL: https://issues.apache.org/jira/browse/HBASE-20430
> Project: HBase
> Issue Type: Sub-task
> Reporter: Andrew Purtell
> Assignee: Mingliang Liu
> Priority: Major
> Labels: s3
>
> HBase keeps a file open for every active store file so no additional round
> trips to the NameNode are needed after the initial open. HDFS internally
> multiplexes open files, but the Hadoop S3 filesystem implementations do not,
> or, at least, not as well. As the bulk of data under management increases we
> observe the required number of concurrently open connections will rise, and
> expect it will eventually exhaust a limit somewhere (the client, the OS file
> descriptor table or open file limits, or the S3 service).
> Initially we can simply introduce an option to close every store file after
> the reader has finished, and determine the performance impact. Use cases
> backed by non-HDFS filesystems will already have to cope with a different
> read performance profile. Based on experiments with the S3 backed Hadoop
> filesystems, notably S3A, even with aggressively tuned options simple reads
> can be very slow when there are blockcache misses, 15-20 seconds observed for
> Get of a single small row, for example. We expect extensive use of the
> BucketCache to mitigate in this application already. Could be backed by
> offheap storage, but more likely a large number of cache files managed by the
> file engine on local SSD storage. If misses are already going to be super
> expensive, then the motivation to do more than simply open store files on
> demand is largely absent.
> Still, we could employ a predictive cache. Where frequent access to a given
> store file (or, at least, its store) is predicted, keep a reference to the
> store file open. Can keep statistics about read frequency, write it out to
> HFiles during compaction, and note these stats when opening the region,
> perhaps by reading all meta blocks of region HFiles when opening. Otherwise,
> close the file after reading and open again on demand. Need to be careful not
> to use ARC or equivalent as cache replacement strategy as it is encumbered.
> The size of the cache can be determined at startup after detecting the
> underlying filesystem. Eg. setCacheSize(VERY_LARGE_CONSTANT) if (fs
> instanceof DistributedFileSystem), so we don't lose much when on HDFS still.
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