[Libevent-users] How do i make a multi-threaded libevent server?

[Robert Iakobashvili]

Hi,

On 4/13/07, Steven Grimm <sgrimm at facebook.com> wrote:
> Martin Hedenfalk wrote:
> > I'm sorry if the above seems harsh, but I really don't see the point
> > in implementing a multi-threaded libevent server.
>
> Adding threads lets you make full use of a
> multiprocessor machine without having to split your application up into
> separate processes. Splitting into multiple processes not only
> duplicates whatever constant overhead each instance of your app has, but
> if the application needs to have globally shared state, you're looking
> at something like a shared memory region or mmapped file with the same
> locking issues you have in a multithreaded app.

Indeed, when HW has several CPUs or cores, etc, starts the business
case for using multi-threading designs despite locking and etc weird
issues to overcome.

Multiprocess designs have pros and cons to consider:
- pros are sometimes higher robustness, when several processes
are doing jobs in parallel; if a single process fails only a portion of the
load goes away (apache design);
- cons are issues with on-fly reconfiguration and management of such
multi-process entities.

My preference is towards multi-threaded rather than multi-process
architecture, where robustness may be enhanced by other means, like
keeping all essential data-structures in memory-mapped file, etc.

Y may wish to look for design using Leader-Followers design pattern
and optimize the number of threads experimentally, where the optimum is in many
cases 2-5 times multiple of CPUs number.


Sincerely,
Robert Iakobashvili,
coroberti %x40 gmail %x2e com
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