basic-supervisor.pl

#!/usr/bin/env perl

use v5.10;
use warnings;
use strict;

use EV;
use AnyEvent;

use Sys::Hostname qw(hostname);

main();

sub main {
	announce_myself();

	# Any state about the workers is stored in this hash, keyed by pid
	my %workers;

	foreach my $worker (1 .. 5) {
		make_child(\%workers);
	}

	say "[$$] new parent here, looking after children for the rest of my life";

	AnyEvent->condvar->recv;
}

sub announce_myself {
	my $hostname = hostname();

	say "[$$] announcing myself to service discovery";

	# Imagine there's more code here to announce this host with
	# service discovery
}

sub make_child {
	my ($worker_state) = @_;

	my $pid = fork;

	# fork() failed, bail out
	if (not defined $pid) {
		die "fork(): $!";
	}

	if ($pid == 0) {
		# Child proc runs here
		child_main();
		exit(0);
	}

	# Parent proc runs here
	my $child_handler = AnyEvent->child(
		pid => $pid,
		cb  => sub {
			say "[$$] child $pid died, respawning a new one...";
			make_child($worker_state);
			delete $worker_state->{$pid};
		},
	);

	$worker_state->{$pid} = {
		child_w => $child_handler,
	};
}

sub child_main {
	say "  [$$] child ready, randomly doing stuff";

	while (1) {
		sleep(rand(10));

		# Imagine some real work is being done here, instead of
		# sleeping for random periods of time
	}
}