restarter.pl

use strict;
use warnings;
use File::Spec;
use FindBin;
use Path::Class;
use File::Modified;
use POSIX ':sys_wait_h';

# -------------------------------------------------------------------------
# configuration part

my @WATCH_DIRS = dir($FindBin::Bin, '..', 'lib');
my $REGEX = qr/\.pm$/;

# -------------------------------------------------------------------------
# code part

&main; exit;

sub main {
    my @child = @ARGV;

    my $files = File::Modified->new(
        files => [ get_file_list(), $0 ]
    );

    my $pid = spawn_child(@child);
    while (1) {
        if (my @changes = $files->changed) {
            for my $fname (@changes) {
                print "$fname was changed\n";
            }
            $files->update;

            kill 15, $pid;
            waitpid $pid, WIFEXITED;
            $pid = spawn_child(@child);
        }
        sleep 1;
    }
}

sub spawn_child {
    my @child = @_;

    if (my $pid = fork()) {
        # parent(watcher)
        return $pid;
    } elsif ($pid == 0) {
        # child(application server)
        exec @child;

        die "cannot reach here";
    } else {
        die "cannot fork";
    }
}

sub get_file_list {
    my @r;
    for my $dir (@WATCH_DIRS) {
        $dir->recurse(
            callback => sub {
                my $f = shift;
                if ($f =~ $REGEX) {
                    push @r, $f;
                }
            }
        );
    }
    return @r;
}