libev: notify only one process when multiple processes are listening socket

[trafdev]

I don't want to introduce threads or IPC mechanisms.

Currently I have a solution where N similar processes are launched from 
command line,
listening on N different ports and there is a balancer which listens on 
one port and forwards requests
to one of N ports in round-robin fashion.
This works and scales very well without unnecessary threads and IPC.

I want to implement same using only one main executable, I believe it's 
possible (one of possibilities is:
    int wrk = thread::hardware_concurrency();
    while (--wrk) {
        pid_t pid = fork();
        if (pid == 0) {
            ev::default_loop().post_fork();
            ev::default_loop().run();
            return true;
        }
    }
    ev::default_loop().run();
    return true;

It works but makes a little overhead on connections acceptance.



On Tue Jul 16 10:17:02 2013, Marc Lehmann wrote:
> On Mon, Jul 15, 2013 at 05:18:33PM -0700, trafdev <trafdev at mail.ru> wrote:
>> N-1 of them getting "resource temporaly unavailable (eagain) while
>> accepting incoming connection, one wins and handles connection.
>>
>> Is it possible to get notification on the socket descriptor only in
>> one process and not waste resources of others?
>
> Use some kind of exclusion mechanism so only one event loop has a watcher
> active at a time, or use only a single shared event loop (e.g. in a
> leader/follower configuration).
>
> Libev or any lower levels cannot help you in this case, as they don't
> know that your application is going to call accept multiple times in the
> future.
>