When is ExecutionHandler necessary

[Frederic Bregier]

Hi Dan,

There is two solutions there.

Either you use an ExecutionHandler in the pipeline since long-running
business task needs to be submitted to another thread pool than I/O thread
(or you will decrease your performance).

Either you internaly submit your job in the handler to your own ThreadPool,
but then you have to take care of the order of new runners (two submission
can execute at the same time from two messages that arrived in order but as
the execution is long, the two threads can overlap each other). Also you
shouldn't wait for anything in the handler from the new sumbitted task since
if you do (waiting on a condition), then your submission is like direct
running and your I/O thread will wait for the end of execution as if you
don't used a thread pool. If this is correct from your business point of
view (sumbitted task without waiting anything in the handler and allowing
overlapping of execution of submitted task - or at least have a control on
it - ), then it is correct.

Generally, OrderedMemoryAwareThreadPoolExecutor does the stuff as needed and
is simpler to implement.

HTH,
Cheers,
Frederic


Dan D wrote:
> 
> Thanks Frederic.  I'm still not clear on whether I can just avoid using
> ExecutionHandler, run long-running business logic directly in the Netty
> I/O
> threads, and rely on using a CachedThreadPool for the Netty I/O threads 
> to
> ensure that there's going to be available threads for Netty to do its
> thing.
> 
> Also, I was wondering whether there was any problem in submitting a task
> to
> my own threadpool from my own handler rather using any ExecutionHandler at
> all (without caring about event ordering or anything like that).
> 
> 
> Date: Sun, 18 Oct 2009 00:24:04 -0700 (PDT)
>> From: Frederic Bregier <fredbregier at free.fr>
>> Subject: Re: When is ExecutionHandler necessary
>> To: netty-users at lists.jboss.org
>> Message-ID: <1255850644557-3843469.post at n2.nabble.com>
>> Content-Type: text/plain; charset=us-ascii
>>
>>
>> Hi Dan,
>>
>> Take a look at the documentation and specifically the API.
>> One advantage of the given ExecutionHandler (specifically
>> OrderedMemoryAwareThreadPoolExecutor) is that message will be kept in
>> order
>> for one channel. If you don't have any such need (message can arrived in
>> any
>> order for any channel), then my believe is that you can use your own
>> ExecutionHandler.
>>
>> Cheers,
>> Frederic
>>
>>
>> Dan D wrote:
>> >
>> > bump
>> >
>> > On Thu, Oct 15, 2009 at 11:10 AM, Dan D <danotsky at gmail.com> wrote:
>> >
>> >> Below, Trustin mentions using an ExecutionHandler for long-running
>> >> business
>> >> logic to prevent tying up Netty's worker threadpool.  If a cached
>> thread
>> >> pool is being used for the worker threads, is this still a problem?
>> >> Won't
>> >> the threadpool just expand as necessary if business logic is tying up
>> >> threads?
>> >>
>> >> Also is an ExecutionHandler required, or can we just submit work to
>> our
>> >> own
>> >> ExecutorService?  If ExecutionHandler isn't required, what are the
>> >> benefits
>> >> to using one?
>> >>
>> >> Thanks.
>> >>
>> >>
>> >>
>> >>> On Tue, Sep 29, 2009 at 3:42 AM, Trustin Lee (???)
>> <trustin at gmail.com>
>> >>> wrote:
>> >>> > Hi Wade,
>> >>> >
>> >>> > If your business logic takes long time, then you should use an
>> >>> > ExecutionHandler. ?Otherwise, other connections will freeze until
>> the
>> >>> > long operation finishes. ?If there's no long operation in your
>> >>> > business logic, you don't usually need an ExecutionHandler in your
>> >>> > pipeline.
>> >>> >
>> >>> > I also suggest to put decoders and encoders before ExecutionHandler
>> >>> > (if there is one), because decoders and encoders usually do
>> CPU-bound
>> >>> > jobs.
>> >>> >
>> >>> > HTH,
>> >>> >
>> >>> > ? Trustin Lee, http://gleamynode.net/
>> >>> >
>> >>>
>> >>
>> >
>> > _______________________________________________
>> > netty-users mailing list
>> > netty-users at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/netty-users
>> >
>> >
>>
>>
>> -----
>> Hardware/Software Architect
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>>
>>
>>
> 
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