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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10855) Use Caffeine (W-TinyLFU) for on-heap caches
Date Sat, 31 Dec 2016 09:58:58 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15789267#comment-15789267
] 

Robert Stupp commented on CASSANDRA-10855:
------------------------------------------

Unit tests look good. However, a couple of dtests fail - unfortunately a situation for which
we do not have a unit test.
Thing is that exception handing in caffeine is different now. It manifests for example in
the catch-clause in {{org.apache.cassandra.auth.PasswordAuthenticator#authenticate}}. The
loader calls {{queryHashedPassword}}, which throws {{org.apache.cassandra.auth.PasswordAuthenticator.NoSuchCredentialsException}}
(extends {{RuntimeException}}). I assume that caffeine just "passes" REs and does not wrap
it in an some {{ExecutionException}}.
Example assertion message from the dtests looks like that's the reason: _'\'Failed to authenticate
to 127.0.0.1: Error from server: code=0100 \[Bad credentials\] message="Provided username
mike and/or password are incorrect"\' not found in \'Failed to authenticate to 127.0.0.1:
Error from server: code=0000 \[Server error\] message="org.apache.cassandra.auth.PasswordAuthenticator$NoSuchCredentialsException"\'_

[~ben.manes] can you verify that REs are just passed through and don't get wrapped in caffeine's
loader mechanism?

||trunk|[branch|https://github.com/apache/cassandra/compare/trunk...snazy:10855-caffeine-trunk]|[testall|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-10855-caffeine-trunk-testall/lastSuccessfulBuild/]|[dtest|http://cassci.datastax.com/view/Dev/view/snazy/job/snazy-10855-caffeine-trunk-dtest/lastSuccessfulBuild/]

> Use Caffeine (W-TinyLFU) for on-heap caches
> -------------------------------------------
>
>                 Key: CASSANDRA-10855
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10855
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Ben Manes
>              Labels: performance
>         Attachments: CASSANDRA-10855.patch, CASSANDRA-10855.patch
>
>
> Cassandra currently uses [ConcurrentLinkedHashMap|https://code.google.com/p/concurrentlinkedhashmap]
for performance critical caches (key, counter) and Guava's cache for non-critical (auth, metrics,
security). All of these usages have been replaced by [Caffeine|https://github.com/ben-manes/caffeine],
written by the author of the previously mentioned libraries.
> The primary incentive is to switch from LRU policy to W-TinyLFU, which provides [near
optimal|https://github.com/ben-manes/caffeine/wiki/Efficiency] hit rates. It performs particularly
well in database and search traces, is scan resistant, and as adds a very small time/space
overhead to LRU.
> Secondarily, Guava's caches never obtained similar [performance|https://github.com/ben-manes/caffeine/wiki/Benchmarks]
to CLHM due to some optimizations not being ported over. This change results in faster reads
and not creating garbage as a side-effect.



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