NAME

MooseX::Workers - Simple sub-process management for asynchronous tasks

SYNOPSIS

 EXAMPLE #1:
    package Manager;
    #    This example prints output from the children normally on both STDOUT and STDERR

    use Moose;
    with qw(MooseX::Workers);

    sub run {
        $_[0]->spawn( sub { sleep 3; print "Hello World\n" } );
        warn "Running now ... ";
        POE::Kernel->run();
    }

    # Implement our Interface
    sub worker_stdout  { shift; warn join ' ', @_;  }
    sub worker_stderr  { shift; warn join ' ', @_;  }

    sub worker_manager_start { warn 'started worker manager' }
    sub worker_manager_stop  { warn 'stopped worker manager' }

    sub max_workers_reached  { warn 'maximum worker count reached' }
    sub worker_error   { shift; warn join ' ', @_;  }
    sub worker_done    { shift; warn join ' ', @_;  }
    sub worker_started { shift; warn join ' ', @_;  }
    sub sig_child      { shift; warn join ' ', @_;  }
    sub sig_TERM       { shift; warn 'Handled TERM' }

    no Moose;

    Manager->new->run();


 EXAMPLE #2:
    package Manager;

    #    This example prints output from the children normally on
    #    STDERR but uses STDOUT to returns a hashref from the child to
    #    the parent

    use Moose;
    with qw(MooseX::Workers);
    use POE qw(Filter::Reference Filter::Line);

    sub run {
        $_[0]->spawn(
            sub {
                sleep 3;

                #    Return a hashref (arrayref, whatever) to the parent using P::F::Reference
                print @{POE::Filter::Reference->new->put([ {msg => "Hello World"} ])}; # Note the [] around the return val

                #    Print normally using P::F::Line (shown for
                #    completeness; in practice, just don't bother
                #    defining the _filter method
                #    
                print STDERR "Hey look, an error message";
            }
        );

        POE::Kernel->run();
    }

    # Implement our Interface
    #    These two are both optional; if defined (as here), they
    #    should return a subclass of POE::Filter.
    sub stdout_filter  { POE::Filter::Reference->new }
    sub stderr_filter  { POE::Filter::Line->new }

    sub worker_stdout  {  
        my ( $self, $result ) = @_;  #  $result will be a hashref:  {msg => "Hello World"} 
                print $result->{msg};

        #    Note that you can do more than just print the message --
        #    e.g. this is the way to return data from the children for
        #    accumulation in the parent.  
        }
    sub worker_stderr  {
        my ( $self, $stderr_msg ) = @_;  #  $stderr_msg will be a string: "Hey look, an error message";
        warn $stderr_msg;
    }

    #     From here down, this is identical to the previous example.
    sub worker_manager_start { warn 'started worker manager' }
    sub worker_manager_stop  { warn 'stopped worker manager' }

    sub max_workers_reached  { warn 'maximum worker count reached' }
    sub worker_error   { shift; warn join ' ', @_;  }
    sub worker_done    { shift; warn join ' ', @_;  }
    sub worker_started { shift; warn join ' ', @_;  }
    sub sig_child      { shift; warn join ' ', @_;  }
    sub sig_TERM       { shift; warn 'Handled TERM' }

    no Moose;

    Manager->new->run();

DESCRIPTION

MooseX::Workers is a Role that provides easy delegation of long-running tasks into a managed child process. Process management is taken care of via POE and its POE::Wheel::Run module.

METHODS

spawn ($command)

fork ($command)

run_command ($command)

These three methods are the whole point of this module. They pass $command through to the MooseX::Worker::Engine which will take care of running $command for you.

spawn() and fork() both invoke POE::Kernel call(), which is synchronous.

run_command() invokes POE::Kernel yield(), which is asynchronous.

If max_workers() has been reached, run_command() warns and does nothing. It is up to you to re-submit $command. See enqueue() if you want us to run $command as soon as another worker is free.

enqueue($command)

Just like run_command(), only that if max_workers() has been set and that number of workers has been reached, then we add $command to a FIFO command queue. As soon as any running worker exits, the first $command in queue (if any) will be run.

check_worker_threshold

This will check to see how many workers you have compared to the max_workers limit. It returns true if the $num_workers is >= $max_workers;

max_workers($count)

An accessor for the maximum number of workers. This is delegated to the MooseX::Workers::Engine object.

has_workers

Check to see if we have *any* workers currently. This is delegated to the MooseX::Workers::Engine object.

num_workers

Return the current number of workers. This is delegated to the MooseX::Workers::Engine object.

meta

The Metaclass for MooseX::Workers::Engine see Moose's documentation.

INTERFACE

MooseX::Worker::Engine supports the following callbacks:

worker_manager_start

Called when the managing session is started

worker_manager_stop

Called when the managing session stops

max_workers_reached

Called when we reach the maximum number of workers

stdout_filter

OPTIONAL. If defined, this should return an object that isa POE::Filter. If it doesn't, the results are undefined. Anything that a child proc sends on STDOUT will be passed through the relevant filter.

stderr_filter

OPTIONAL. If defined, this should return an object that isa POE::Filter. If it doesn't, the results are undefined. Anything that a child proc sends on STDERR will be passed through the relevant filter.

worker_stdout

Called when a child prints to STDOUT. If stdout_filter was defined, the output will be filtered appropriately, as described above. This is useful to allow child processes to return data to the parent (generally via POE::Filter::Reference).

worker_stderr

Called when a child prints to STDERR. Filtered through the result of stderr_filter if that method is defined.

worker_error

Called when there is an error condition detected with the child.

worker_done

Called when a worker completes $command

worker_started

Called when a worker starts $command

sig_child

Called when the mangaging session recieves a SIG CHLD event

sig_*

Called when the underlying POE Kernel receives a signal; this is not limited to OS signals (ie. what you'd usually handle in Perl's %SIG) so will also accept arbitrary POE signals (sent via POE::Kernel->signal), but does exclude SIGCHLD/SIGCHILD, which is instead handled by sig_child above.

These interface methods are automatically inserted when MooseX::Worker::Engine detects that your manager class contains any methods beginning with sig_. Signals are case-sensitive, so if you wish to handle a TERM signal, you must define a sig_TERM() method. Note also that this action is performed upon MooseX::Worker::Engine startup, so any run-time modification of your class which 'does' MooseX::Workers is not likely to be detected.

See the sig_TERM handler in the SYNOPSIS for an example.

See MooseX::Workers::Engine for more details. Also see MooseX::Workers::Job if you'd like to give your tasks names, or set timeouts on them.

DEPENDENCIES

Moose, POE, POE::Wheel::Run

BUGS AND LIMITATIONS

Please report any bugs or feature requests to bug-moosex-workers@rt.cpan.org, or through the web interface at http://rt.cpan.org.

Version control: https://github.com/jhannah/moosex-workers

AUTHORS

Chris Prather <perigrin@cpan.org>

Tom Lanyon <dec@cpan.org>

Jay Hannah <jay@jays.net>

Justin Hunter <justin.d.hunter@gmail.com>

David K. Storrs <david.storrs@gmail.com>

LICENCE AND COPYRIGHT

Copyright (c) 2007-2011, Chris Prather <perigrin@cpan.org>. Some rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.