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From Enis Söztutar <e...@apache.org>
Subject Re: Disk space leak when using HBase and HDFS ShortCircuit
Date Thu, 26 Jun 2014 00:02:39 GMT
Agreed, this seems like an hdfs issue unless hbase itself does not close
the hfiles properly. But judging from the fact that you were able to
circumvent the problem by getting reducing the cache size, it does seem

I don't think the local block reader will be notified when a file/block is

What was your dfs.client.read.shortcircuit.streams.cache.size ?


On Wed, Jun 25, 2014 at 3:29 PM, Andrew Purtell <apurtell@apache.org> wrote:

> Forwarded
> ---------- Forwarded message ----------
> From: Vladimir Rodionov <vrodionov@carrieriq.com>
> Date: Wed, Jun 25, 2014 at 12:03 PM
> Subject: RE: Disk space leak when using HBase and HDFS ShortCircuit
> To: "user@hbase.apache.org" <user@hbase.apache.org>
> >> Apparently those file descriptors were stored by the HDFS
> >> ShortCircuit cache.
> As far as I understand this is issue of HDFS shorty-circuit-reads
> implementation not HBase. HBase uses HDFS API to access
> files. Did you ask this question on hdfs dev list? This looks like a very
> serious bug.
> Best regards,
> Vladimir Rodionov
> Principal Platform Engineer
> Carrier IQ, www.carrieriq.com
> e-mail: vrodionov@carrieriq.com
> ________________________________________
> From: Giuseppe Reina [g.reina@gmail.com]
> Sent: Wednesday, June 25, 2014 2:54 AM
> To: user@hbase.apache.org
> Subject: Disk space leak when using HBase and HDFS ShortCircuit
> Hi all,
>    we have been experiencing the same problem with 2 of our clusters. We
> are currently using HDP 2.1 that comes with HBase 0.98.
> The problem manifested by showing a huge differences (hundreds of GB)
> between the output of "df" and "du" of the hdfs data directories.
> Eventually, other systems complained for the lack of space before shutting
> down. We identified the problem and discovered that all the RegionServers
> were holding lots of open file descriptors to deleted files, which
> prevented the OS to free the disk space occupied (hence the difference
> between "df" and "du"). The deleted files were pointing to the local HDFS
> blocks of old HFiles deleted from HDFS during the compaction and/or split
> operations. Apparently those file descriptors were stored by the HDFS
> ShortCircuit cache.
> My question is, isn't the shortcircuit feautre supposed to get "notified"
> somehow of file deletion on a file on HDFS so it can remove the open fds
> from the cache? This creates huge leaks whenever HBase is heavily loaded
> and we had to restart the RegionServer periodically until before
> identifying the problem. We solved the problem first by disabling
> shortcircuit from HDFS and then enabling it and reducing the cache size so
> to trigger often the caching policies (this leads to some performance
> loss).
> p.s. I am aware of the "
> dfs.client.read.shortcircuit.streams.cache.expiry.ms
> " directoparameter, but for some reason the default value (5 mins) does not
> work out-of-the-box on HDP 2.1, moreover the problem persists for high
> timeouts and big cache sizes.
> Kind Regards
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> Best regards,
>    - Andy
> Problems worthy of attack prove their worth by hitting back. - Piet Hein
> (via Tom White)

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