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

[Steven Grimm]

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.

I can answer that, since I converted memcached from single- to 
multi-threaded: even if each request completes in a very short time, 
pile enough of them up in a short period of time and you'll run out of 
capacity on one CPU. 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.

As for how to do it, my approach is documented on the libevent home page 
(or rather, there's a link there to my explanation) so I won't repeat 
myself. But I will say it's working well for us -- our memcached 
instances are handling close to twice the request volume they used to be 
able to handle when they were single-threaded, and they still have 
plenty of capacity to spare.

-Steve