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https://issues.apache.org/jira/browse/HDFS-10872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15589917#comment-15589917
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Andrew Wang commented on HDFS-10872:
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Thanks for the replies, Erik, Zhe, inline:
bq. Are we aware of any production usage of this library?
The popular codahale/Dropwizard metrics library pulls in LongAdder in the
manner I suggested, so it might be easiest to add that as a dependency. I'm
pretty sure we already have it floating around in Hadoop somewhere. The quality
of JDK code is also well regarded.
bq. For something like MutableCounter a LongAdder would be great, but I am
wondering if we can make it apply here?
Looking at [EWMA in
codahale|https://github.com/dropwizard/metrics/blob/3.2-development/metrics-core/src/main/java/com/codahale/metrics/EWMA.java],
they reset a LongAdder without additional synchronization with updates.
Metrics don't need to be super precise, so as long as there isn't a disastrous
concurrent failure mode, this is okay.
Unless we really need the additional bits of MutableRate, the simplest thing
might be to wrap the Dropwizard metrics classes like Histogram and EWMA to fit
in the Hadoop metrics system.
> Add MutableRate metrics for FSNamesystemLock operations
> -------------------------------------------------------
>
> Key: HDFS-10872
> URL: https://issues.apache.org/jira/browse/HDFS-10872
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Attachments: FSLockPerf.java, HDFS-10872.000.patch,
> HDFS-10872.001.patch, HDFS-10872.002.patch, HDFS-10872.003.patch,
> HDFS-10872.004.patch
>
>
> Add metrics for FSNamesystemLock operations to see, overall, how long each
> operation is holding the lock for. Use MutableRate metrics for now.
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