NAME
    Parallel::Prefork - A simple prefork server framework

SYNOPSIS
      use Parallel::Prefork;
  
      my $pm = Parallel::Prefork->new({
        max_workers  => 10,
        trap_signals => {
          TERM => 'TERM',
          HUP  => 'TERM',
          USR1 => undef,
        }
      });
  
      while ($pm->signal_received ne 'TERM') {
        load_config();
        $pm->start(sub {
            ... do some work within the child process ...
        });
      }
  
      $pm->wait_all_children();

DESCRIPTION
    "Parallel::Prefork" is much like "Parallel::ForkManager", but supports
    graceful shutdown and run-time reconfiguration.

METHODS
  new
    instantiation. Takes a hashref as an argument. Recognized attributes are
    as follows.

   max_workers
    number of worker processes (default: 10)

   spawn_interval
    interval in seconds between spawning child processes unless a child
    process exits abnormally (default: 0)

   err_respawn_interval
    number of seconds to deter spawning of child processes after a worker
    exits abnormally (default: 1)

   trap_signals
    hashref of signals to be trapped. Manager process will trap the signals
    listed in the keys of the hash, and send the signal specified in the
    associated value (if any) to all worker processes. If the associated
    value is a scalar then it is treated as the name of the signal to be
    sent immediately to all the worker processes. If the value is an
    arrayref the first value is treated the name of the signal and the
    second value is treated as the interval (in seconds) between sending the
    signal to each worker process.

   on_child_reap
    coderef that is called when a child is reaped. Receives the instance to
    the current Parallel::Prefork, the child's pid, and its exit status.

   before_fork
   after_fork
    coderefs that are called in the manager process before and after fork,
    if being set

  start
    The main routine. There are two ways to use the function.

    If given a subref as an argument, forks child processes and executes
    that subref within the child processes. The processes will exit with 0
    status when the subref returns.

    The other way is to not give any arguments to the function. The function
    returns undef in child processes. Caller should execute the application
    logic and then call "finish" to terminate the process.

    The "start" function returns true within manager process upon receiving
    a signal specified in the "trap_signals" hashref.

  finish
    Child processes (when executed by a zero-argument call to "start")
    should call this function for termination. Takes exit code as an
    optional argument. Only usable from child processes.

  signal_all_children
    Sends signal to all worker processes. Only usable from manager process.

  wait_all_children()
  wait_all_children($timeout)
    Waits until all worker processes exit or timeout (given as an optional
    argument in seconds) exceeds. The method returns the number of the
    worker processes still running.

AUTHOR
    Kazuho Oku

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

    See http://www.perl.com/perl/misc/Artistic.html