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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16142) Trigger JFR session when under duress -- e.g. backed-up request queue count -- and dump the recording to log dir
Date Thu, 30 Jun 2016 19:14:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15357676#comment-15357676

stack commented on HBASE-16142:

Yes, off by default though I think I'd like to enable these flags by default -XX:+UnlockCommercialFeatures
-XX:+FlightRecorder (as long as they are ignored by other JVMs and don't pull down perf (they
don't in my experience).

Yes [~mantonov], this would not be tracing. It would be something that flipped on programmatically
when struggling. It would bring down the perf by a few percent but the upside would be good
detail on what was going on in JVM during the struggle.

> Trigger JFR session when under duress -- e.g. backed-up request queue count -- and dump
the recording to log dir
> ----------------------------------------------------------------------------------------------------------------
>                 Key: HBASE-16142
>                 URL: https://issues.apache.org/jira/browse/HBASE-16142
>             Project: HBase
>          Issue Type: Task
>          Components: Operability
>            Reporter: stack
>            Priority: Minor
>              Labels: beginner
> Chatting today w/ a mighty hbase operator on how to figure what is happening during transitory
latency spike or any other transitory 'weirdness' in a server, the idea came up that a java
flight recording during a spike would include a pretty good picture of what is going on during
the time of duress (more ideal would be a trace of the explicit slow queries showing call
stack with timings dumped to a sink for later review; i.e. trigger an htrace when a query
is slow...).
> Taking a look, programmatically triggering a JFR recording seems doable, if awkward (MBean
invocations). There is even a means of specifying 'triggers' based off any published mbean
emission -- e.g. a query queue count threshold -- which looks nice. See https://community.oracle.com/thread/3676275?start=0&tstart=0
and https://docs.oracle.com/javacomponents/jmc-5-4/jfr-runtime-guide/run.htm#JFRUH184
> This feature could start out as a blog post describing how to do it for one server. A
plugin on Canary that looks at mbean values and if over a configured threshold, triggers a
recording remotely could be next. Finally could integrate a couple of triggers that fire when
issue via the trigger mechanism.
> Marking as beginner feature.

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