File Coverage

blib/lib/Beam/Runnable/Single.pm

Criterion	Covered	Total	%
statement	12	12	100.0
branch			n/a
condition			n/a
subroutine	4	4	100.0
pod			n/a
total	16	16	100.0

package Beam::Runnable::Single;
our $VERSION = '0.016';
# ABSTRACT: Only allow one instance of this command at a time

#pod =head1 SYNOPSIS
#pod
#pod     ### In a Runnable module
#pod     package My::Runnable::Script;
#pod     use Moo;
#pod     with 'Beam::Runnable', 'Beam::Runnable::Single';
#pod     has '+pid_file' => ( default => '/var/run/runnable-script.pid' );
#pod     sub run { }
#pod
#pod     ### In a container config file
#pod     runnable:
#pod         $class: My::Runnable::Script
#pod         $with:
#pod             - 'Beam::Runnable::Single'
#pod         pid_file: /var/run/runnable-script.pid
#pod
#pod =head1 DESCRIPTION
#pod
#pod This role checks to ensure that only one instance of the command is
#pod running at a time. If another instance tries to run, it dies with an
#pod error instead.
#pod
#pod Users should have access to read/write the path pointed to by
#pod L, and to read/write the directory containing the PID file.
#pod
#pod If the command exits prematurely, the PID file will not be cleaned up.
#pod If this is undesirable, make sure to trap exceptions in your C
#pod method and return the exit code you want.
#pod
#pod =head1 SEE ALSO
#pod
#pod L
#pod
#pod =cut

use strict;
use warnings;
use Moo::Role;
use Types::Path::Tiny qw( Path );

#pod =attr pid_file
#pod
#pod The path to a file containing the PID of the currently-running script.
#pod
#pod =cut

has pid_file => (
    is => 'ro',
    isa => Path,
    required => 1,
    coerce => 1,
);

#pod =method run
#pod
#pod This role wraps the C method of your runnable class to check that
#pod there is no running instance of this task (the PID file does not exist).
#pod
#pod =cut

before run => sub {
    my ( $self, @args ) = @_;
    if ( $self->pid_file->exists ) {
        my $pid = $self->pid_file->slurp;
        die "Process already running (PID: $pid)\n";
    }
    $self->pid_file->spew( $$ );
};

after run => sub {
    my ( $self ) = @_;
    unlink $self->pid_file;
};

1;

__END__