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From Remko Popma <remko.po...@gmail.com>
Subject Re: why is AsyncLoggerContextSelector faster?
Date Mon, 21 Jul 2014 14:47:21 GMT
Matt, not sure what you mean. Mariano needs to develop his own
ContextSelector to achieve log separation.
So he cannot use the AsyncLoggerContextSelector.

Mariano, I would not be overly concerned with the performance results
mentioned on the async logger manual page. Bear in mind that in that
performance test, _all_ that the program does is logging. In the real world
(your application) that will obviously not be true: your application will
do many other things.

Also, mixed async loggers performed much, much better than AsyncAppenders.

So, unless you have actual measurement numbers for _your_ application, not
the theoretical numbers from the async logger manual page, I would keep it
simple at first, just get your custom selector to work well, and then start
measuring performance.

If you are getting strange results, like AsyncAppenders performing better
than AsyncLoggers, then let us know and we'll try to help figure out what
the problem is.



On Mon, Jul 21, 2014 at 11:38 PM, Matt Sicker <boards@gmail.com> wrote:

> Well, the way to go that's similar to the async version is to use the
> BasicContextSelector which contains a singleton LoggerContext. Otherwise,
> you'll have to keep your own registry that can be looked up dynamically
> such as through reflection of the caller stack and other fun design
> problems. :)
>
>
> On 21 July 2014 09:35, Mariano Gonzalez <mariano.l.gonzalez@gmail.com>
> wrote:
>
> > Hello Remko,
> >
> > I'm still a couple of days away from starting my own performance testing.
> > I'm taking about the difference in the async loggers manual page, more
> > specifically, the charts that compare sync loggers, to mixed async
> loggers
> > against purely async loggers. Since I need to build my own selector, I'm
> > trying to be clear on how this works internally in order to implement the
> > less latency possible selector and try to minimize the performance
> testing
> > effort.
> >
> > Thanks for the clarifications!
> >
> >
> >
> > On Mon, Jul 21, 2014 at 11:22 AM, 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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