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From Mariano Gonzalez <mariano.l.gonza...@gmail.com>
Subject Re: why is AsyncLoggerContextSelector faster?
Date Mon, 21 Jul 2014 14:10:41 GMT
Hello Remko,

I think I found the difference. AsyncLoggerContextSelector always returns
the same instance of AsyncLoggerContext, which in turns always returns
instances of AsyncLogger, which uses disruptor to handle concurrency.

However, with any other selector, a standard Logger instance is returned
and parallelism is achieved through an AsyncAppender. AsyncAppender use a
standard blocking queue instead of using disruptor which explains the
performance difference (there's also the fact that
AsyncLoggerContextSelector always returns the same context instance and
does not spend cycles in the lookup, but I think that is not a significant
cost once everything was warmed out).

http://logging.apache.org/log4j/2.x/manual/async.html says that when using
mixed type loggers disruptor is needed on the classpath. That seems to be
an error. For what I see disruptor is only used when setting all loggers
asynchronous.

Does this make sense? Anyway around this? Do you have a disruptor appender
somewhere?

Thanks!


On Sat, Jul 19, 2014 at 11:55 PM, Remko Popma <remko.popma@gmail.com> wrote:

> To be honest, I haven't investigated in detail the reason for the
> difference in throughput in the performance test.
>
> Are you measuring the performance of your application container, and can
> you see an improvement when using Async Loggers?
> Do you see a large difference in performance _in your application_ between
> making all loggers Asynchronous and using mixed synchronous and
> Asynchronous loggers?
>
>
> On Sun, Jul 20, 2014 at 7:45 AM, Mariano Gonzalez <
> mariano.l.gonzalez@gmail.com> wrote:
>
> > Hello Remko,
> >
> > Thanks for the insight. I guess my case falls into the wrong end of the
> > pareto law. My project is a low latency application container, so I need
> to
> > have:
> >
> >
> >    - low latency
> >    - log separation (I actually had to implement my own context selector
> >    because my logic is more complicated than the standard
> >    ClassLoaderContextSelector case)
> >    - I want async loggers by default, but deployed apps need to be able
> to
> >    specify sync loggers
> >
> >
> > Right now I'm kinda meeting those requirements using config file,
> AsyncRoot
> > and my custom selector, but it'd be really great to achieve a performance
> > level like the one that AsyncContextSelector promises.
> >
> > Is there a way of doing that? For what I see on the code, the
> > AsyncLoggerContextSelector's secret sauce is just to always return an
> > AsyncLogger on the newInstance() method. Why is that so much faster than
> > what ClassLoaderLoggerContextSelector does?
> >
> > Thanks!
> >
> >
> > On Fri, Jul 18, 2014 at 1:20 PM, Remko Popma <remko.popma@gmail.com>
> > wrote:
> >
> > > The Async Loggers created with the context selector have a slightly
> > > different mechanism. One of the differences is that LogEvent objects
> are
> > > re-used.
> > >
> > > However, unless your application is in the low-latency space, I would
> not
> > > worry too much about the performance difference. Both flavors of Async
> > > Loggers are much faster than the alternative (Async Appenders).
> > >
> > > Your point is valid though. I've been thinking about an alternative way
> > to
> > > configure Async Loggers than via system properties. The work in
> progress
> > is
> > > tracked in Jira ticket LOG4J2-321
> > > <https://issues.apache.org/jira/browse/LOG4J2-321>. This is still in
> the
> > > concept phase though. Meanwhile your best option is probably to use
> > > ClassLoaderContextSelector and configure with <AsyncRoot> and
> > > <AsyncLogger>.
> > >
> > >
> > >
> > > On Fri, Jul 18, 2014 at 10:57 PM, Mariano Gonzalez <
> > > mariano.l.gonzalez@gmail.com> wrote:
> > >
> > > > Hello,
> > > >
> > > > According to the performance charts in the documentation, log4j2 has
> a
> > > > significantly higher throughput when using AsyncLoggerContextSelector
> > > than
> > > > when using all async loggers with any different selector.
> > > >
> > > > Why is that? Is it just because the same context is always reused and
> > > > there's no lookup like in the ClassLoaderContextSelector case?
> > > >
> > > > If I need functionality similar to ClassLoaderContextSelector, is
> there
> > > any
> > > > way to get a throughput similar to AsyncLoggerContextSelector?
> > > >
> > > > Thanks!
> > > >
> > >
> >
>

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