NAME

    Parallel::Runner - An object to manage running things in parallel
    processes.

DESCRIPTION

    There are several other modules to do this, you probably want one of
    them. This module exists as a super specialised parallel task manager.
    You create the object with a process limit and callbacks for what to do
    while waiting for a free process slot, as well as a callback for what a
    process should do just before exiting.

    You must explicitly call $runner->finish() when you are done. If the
    runner is destroyed before it's children are finished a warning will be
    generated and your child processes will be killed, by force if
    necessary.

    If you specify a maximum of 1 then no forking will occur, and run()
    will block until the coderef returns. You can force a fork by providing
    a boolean true value as the second argument to run(), this will force
    the runner to fork before running the coderef, however run() will still
    block until it the child exits.

SYNOPSYS

        #!/usr/bin/perl
        use strict;
        use warnings;
        use Parallel::Runner;
    
        my $runner = Parallel::Runner->new(4);
        $runner->run( sub { ... } );
        $runner->run( sub { ... } );
        $runner->run( sub { ... } );
        $runner->run( sub { ... } );
    
        # This will block until one of the previous 4 finishes
        $runner->run( sub { ... } );
    
        # Do not forget this.
        $runner->finish;

CONSTRUCTOR

    $runner = $class->new( $max, $accessor => $value, ... );

      Create a new instance of Parallel::Runner. $accessor can be anything
      listed under the ACCESSORS section. $max should be the maximum number
      of processes allowed, defaults to 1.

ACCESSORS

    These are simple accessors, providing an argument sets the accessor to
    that argument, no argument it simply returns the current value.

    $val = $runner->data_callback( \&callback )

      If this is specified than IPC will be automatically enabled, and the
      final return from each process will be passed into this handler in
      the main process. Due to the way IPC works only strings/numerical
      data is passed, if you need to pass a ref you will need to serialize
      it yourself before returning it, followed by deserializing it in your
      callback.

      Example:

          # Place to put the accumulated data
          my @accum_data;
      
          # Create the runner with a callback that pushes the data onto our array.
          $runner = $CLASS->new( 2,
              data_callback => sub {
                  my ($data) = @_;
                  push @accum_data => $data;
              },
          );
      
          # 4 processes that return data
          $runner->run( sub { return "foo" });
          $runner->run( sub { return "bar" });
          $runner->run( sub { return "baz" });
          $runner->run( sub { return "bat" });
          $runner->finish;
      
          # Verify the data (order is not predictable)
          is_deeply(
              [ sort @accum_data ],
              [ sort qw/foo bar baz bat/ ],
              "Got all data returned by subprocesses"
          );

    $val = $runner->exit_callback( \&callback )

      Codref to call just before a child exits (called within child)

    $val = $runner->iteration_delay( $float );

      How long to wait per iterate if nothing has changed.

    $val = $runner->iteration_callback( $newval )

      Coderef to call multiple times in a loop while run() is blocking
      waiting for a process slot.

    $val = $runner->reap_callback( $newval )

      Codref to call whenever a pid is reaped using waitpid. The callback
      sub will be passed 3 values The first is the exit status of the child
      process. The second is the pid of the child process. The third used
      to be the return of waitpid, but this is deprecated as Child is now
      used and throws an exception when waitpid is not what it should be.
      The third is simply the pid of the child process again. The final
      argument is the child process object itself.

          $runner->reap_callback( sub {
              my ( $status, $pid, $pid_again, $proc ) = @_;
      
              # Status as returned from system, so 0 is good, 1+ is bad.
              die "Child $pid did not exit 0"
                  if $status;
          });

    @children = $runner->children( @append )

      Returns a list of Child::Link::Proc objects.

    $val = $runner->pid()

      pid of the parent process

    $val = $runner->max( $newval )

      Maximum number of children

OBJECT METHODS

    run( $code )

    run( $code, $force_fork )

      Run the specified code in a child process. Blocks if no free slots
      are available. Force fork can be used to force a fork when max is 1,
      however it will still block until the child exits.

    finish()

    finish( $timeout )

    finish( $timeout, $timeoutcallback )

      Wait for all children to finish, then clean up after them. If a
      timeout is specified it will return after the timeout regardless of
      wether or not children have all exited. If there is a timeout call
      back then that code will be run upon timeout just before the method
      returns.

      NOTE: DO NOT LET YOUR RUNNER BE DESTROYED BEFORE FINISH COMPLETES
      WITHOUT A TIMEOUT.

      the runner will kill all children, possibly with force if your runner
      is destroyed with children still running, or not waited on.

    killall( $sig )

      Send all children the specified kill signal.

    DESTROY()

      Automagically called when the object is destroyed. If called while
      children are running it will forcefully clean up after you as
      follows:

      1) Sends an ugly warning.

      2) Will first give all your children 1 second to complete.

      Windows) Strawberry fails with processes, so on windows DESTROY will
      wait as long as needed, possibly forever.

      3) Sends kill signal 15 to all children then waits up to 4 seconds.

      4) Sends kill signal 9 to any remaining children then waits up to 10
      seconds

      5) Gives up and returns

FENNEC PROJECT

    This module is part of the Fennec project. See Fennec for more details.
    Fennec is a project to develop an extendable and powerful testing
    framework. Together the tools that make up the Fennec framework provide
    a potent testing environment.

    The tools provided by Fennec are also useful on their own. Sometimes a
    tool created for Fennec is useful outside the greater framework. Such
    tools are turned into their own projects. This is one such project.

    Fennec - The core framework

      The primary Fennec project that ties them all together.

AUTHORS

    Chad Granum exodist7@gmail.com

COPYRIGHT

    Copyright (C) 2010 Chad Granum

    Parallel-Runner is free software; Standard perl licence.

    Parallel-Runner is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the license
    for more details.

