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From Matt Sicker <boa...@gmail.com>
Subject Re: why is AsyncLoggerContextSelector faster?
Date Mon, 21 Jul 2014 14:30:53 GMT
I think he's talking about the ClassLoaderContextSelector which attempts to
find the logger context through several different ways. Using the
sun.reflect.Reflection class to get the caller class itself is one of those
techniques which might slow things down a little.

I actually have a change to LogManager that can help speed up LoggerContext
resolution when you create a Logger using a Class<?> instead of a String.
The ClassLoader of that Class should be passed to the LoggerContextFactory
to help speed up resolution of the appropriate LoggerContext.


On 21 July 2014 09:22, Remko Popma <remko.popma@gmail.com> wrote:

> Hi,
> No that is incorrect.
> If you do not specify AsyncLoggerContextSelector but instead configure with
> <AsyncRoot> and <AsyncLogger> loggers, you _do_ need the disruptor jar on
> the classpath and this does _not_ use AsyncAppender. AsyncAppender is
> completely separate from Async Loggers. Async Loggers (mixed or all async)
> use the disruptor and both need the disruptor jar.
>
> You keep mentioning a performance difference. I was assuming you were
> talking about the performance test results mentioned on the Async Logger
> manual page, but perhaps I was wrong? Are you experiencing a performance
> difference between the two flavors of Async Loggers in your application?
>
>
>
>
> On Mon, Jul 21, 2014 at 11:10 PM, Mariano Gonzalez <
> mariano.l.gonzalez@gmail.com> wrote:
>
> > 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!
> > > > > >
> > > > >
> > > >
> > >
> >
>



-- 
Matt Sicker <boards@gmail.com>

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