I wonder if someone could help me understand how fork and wait works. I may do the right thing, but I may also have missed something fundamental here.

Consider the following HTTP::Daemon code (simplified from my scenario), pretty much snipped from the synopsis, with forking added. 

my $d = HTTP::Daemon->new(
        LocalPort => $self->port(),
        ReuseAddr => 1,
        );

$SIG{CLD} = $SIG{CHLD} = 'IGNORE';

while (my $c = $d->accept()) {

    next if(fork());
    
    $SIG{CLD} = $SIG{CHLD} = 'DEFAULT';  #Reset child signal handler

    while (my $r = $c->get_request()) {

        # ... do stuff here, including a system() call

        }
    $c->close;
    undef($c);
    
    exit(0);
}

[download]

At first, the fork left zombies. So I Googled for that, and figured I need a wait() or IGNORE handler. So I added that. The zombies went away.

But, instead I got problems with a system() call. It failed and $! was "No child processes". Huh?

My guess is that now it's the child signal handler that's messing this up, so I reset it to 'DEFAULT' after the fork. This seems to solve the problem and the system() works fine again.

Is this correct? Or did I just manage to fix the symptom instead of the problem?


/J

In reply to Understanding fork + wait by jplindstrom

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