Re^2: How to pass AnyEvent socket handle to pre-forked child process?

[michaelfung]

I can't use accept() as it is not accessible in AnyEvent.

[Corion]

If whatever you receive actually is a filehandle, or even better, a socket, then you need to maybe wrap it with an AnyEvent::Handle. Looking at AnyEvent::Beanstalk, I don't see how to pass sockets around with it though.

[michaelfung]

Thanks Corion. But I just think of a different approach: use a tcp load balancer to distribute traffic to pre-forked children listening on different ports of localhost.

[zwon]

You can use accept, you just should ensure that it will not block. Make server socket non-blocking, add read watcher to it, in read callback accept all connections. Something like:

use AnyEvent::Util qw(fh_nonblocking);
...;
fh_nonblocking $srv_sock, 1;
my $w = AE::io $srv_sock, 0, sub {
    while(accept my $cli_sock, $srv_sock) {
        # initialize watchers for client socket
    }
};

[michaelfung]

Thanks Pavel! Now I know that sockets can be shared between forked childen.

The following skeleton worked for me:

# parent domain
...
my $server_socket = IO::Socket::INET->new(        
    Listen => 5,
        ReuseAddr => 1,
    LocalAddr => 'a.b.c.d',    
    LocalPort => nnnn,
    Blocking  => 0    
) 

# fork n children ...

# child domain:
fh_nonblocking $server_socket, 1;
my $w = AE::io $server_socket, 0, sub {
  while(accept my $client_socket, $server_socket) {
    # setup handlers for this new client: 
    $handles->{$client_id} = new AnyEvent::Handle(
      fh => $client_socket,
      on_read => sub { ... },
      on_error => sub { ... },
    );    
   $handles->{$client_id}->push_write ("Child $child_no welcome client
+ $client_id \015\012");
...