NAME

       Parallel::Prefork::SpareWorkers - A prefork server framework with support for
       (min|max)spareservers

SYNOPSIS

         use Parallel::Prefork::SpareWorkers qw(:status);

         my $pm = Parallel::Prefork::SpareWorkers->new({
           max_workers       => 40,
           min_spare_workers => 5,
           max_spare_workers => 10,
           trap_signals      => {
             TERM => 'TERM',
             HUP  => 'TERM',
             USR1 => undef,
           },
         });

         while ($pm->signal_received ne 'TERM') {
           load_config();
           $pm->start and next;

           # do what ever you like, as follows
           while (my $sock = $listener->accept()) {
             $pm->set_status('A');
             ...
             $sock->close();
             $pm->set_status(STATUS_IDLE);
           }

           $pm->finish;
         }

         $pm->wait_all_children;

DESCRIPTION

       "Parallel::Prefork::SpareWorkers" is a subclass of "Parallel::Prefork" that supports
       setting minimum and maximum number of spare worker processes, a feature commonly found in
       network servers.  The module adds to "Parallel::Prefork" several initialization
       parameters, constants, and a method to set state of the worker processes.

METHODS

   new
       Instantiation.  "Parallel::Prefork::ShpareWorkers" recognizes the following parameters in
       addition to those defined by "Parallel::Prefork".  The parameters can be accessed using
       accessors with same names as well.

       min_spare_workers

       minimum number of spare workers (mandatory)

       max_spare_workers

       maxmum number of spare workers (default: max_workers)

       heartbeat

       a fractional period (in seconds) of child amount checking. Do not use very small numbers
       to avoid frequent use of CPU (default: 0.25)

       scoreboard_file

       filename of scoreboard.  If not set, "Parallel::Prefork::SpareWorkers" will create a
       temporary file.

   set_status
       sets a single-byte character state of the worker process.  Worker processes should set any
       character of their choice using the function (but not one of the reserved characters) to
       declare that it is running some kind of task.  Or the state should be set to "STATUS_IDLE"
       '_' once the worker enters idle state.  The other reserved character is "STATUS_NEXIST"
       '.' which should never be set directly by applications.

CONSTANTS

   STATUS_NEXIST
       scoreboard status character '.', meaning no worker process is assigned to the slot of the
       scoreboard.  Applications should never set this value directly.

   STATUS_IDLE
       scoreboard status character '_', meaning that a worker process is in idle state

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