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https://issues.apache.org/jira/browse/HBASE-3287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965489#action_12965489
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HBase Review Board commented on HBASE-3287:
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Message from: "Jonathan Gray" <jg...@apache.org>
bq. On 2010-11-30 09:57:27, Ryan Rawson wrote:
bq. > branches/0.90/src/main/java/org/apache/hadoop/hbase/io/hfile/HFile.java,
line 765
bq. > <http://review.cloudera.org/r/1261/diff/1/?file=17902#file17902line765>
bq. >
bq. > why would you not want to evict blocks from the cache on close?
bq.
bq. stack wrote:
bq. I think this a good point. Its different behavior but its behavior we
should have always had? One less option too.
bq.
bq. Ryan Rawson wrote:
bq. I'm still confused why we are adding config for something that we
should always be doing it. While we'll never be zero conf, I am not seeing the
reason why we'd want to keep things in the LRU.
bq.
bq. It would make more sense not to evict on a split, but evict every
other time, since a split will probably reopen the same hfiles and need those
blocks again.
bq.
bq. Jonathan Gray wrote:
bq. I think it makes sense to have undocumented configuration parameters.
The default behavior is then "the way" but having a config option checked in
the code at least gives the opportunity to turn something on/off without making
a code change and redeploying completely. In the unit test, I'm turning it
on/off with the config parameter so I can verify it works as expected.
bq.
bq. And although I've changed the default to true, I'm not convinced that
it always makes sense in all cases.
bq.
bq. Ryan came up with example of the split, though that would override the
config parameter. But I think there could be other situations where you don't
want to as well.
bq.
bq. In any case, I want to keep it configurable so I can turn it on/off
between test runs and see what, if any, difference these optimizations make and
IMO there's very little cost associated with using
conf.getBoolean("some.undocumented.thing", true) vs. a hard-coded true (if
there's any possibility you might want to change the behavior).
Filed HBASE-3289 to disable them on close of parent files during split. I
looked at the code and it's a fairly significant change since we'll need to
pass a boolean in to all of the close() methods (there are several levels of
them).
Also, figuring out when we do want to evict these blocks (once both children
have closed the file) is tricky.
- Jonathan
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> Add option to cache blocks on hfile write and evict blocks on hfile close
> -------------------------------------------------------------------------
>
> Key: HBASE-3287
> URL: https://issues.apache.org/jira/browse/HBASE-3287
> Project: HBase
> Issue Type: New Feature
> Components: io, regionserver
> Affects Versions: 0.90.0
> Reporter: Jonathan Gray
> Assignee: Jonathan Gray
> Fix For: 0.92.0
>
> Attachments: HBASE-3287-FINAL-trunk.patch
>
>
> This issue is about adding configuration options to add/remove from the block
> cache when creating/closing files. For use cases with lots of flushing and
> compacting, this might be desirable to prevent cache misses and maximize the
> effective utilization of total block cache capacity.
> The first option, {{hbase.rs.cacheblocksonwrite}}, will make it so we
> pre-cache blocks as we are writing out new files.
> The second option, {{hbase.rs.evictblocksonclose}}, will make it so we evict
> blocks when files are closed.
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