NAME Parallel::PreForkManager - A manager for pre-forked child worker processes DESCRIPTION Once upon a time, there were X modules on CPAN for managing worker processes, none of the ones I looked at worked in quite the way I wanted, so now there are X+1. Easy management of child worker processes. This module manages a pool of child worker processes, these work through a list of jobs returning the results to the parent process. Each child can be made to exit and respawn after a set number of jobs, and can call back to methods in the parent process if required. Methods can be defined for child setup and teardown. SYNOPSIS use Parallel::PreForkManager; use English qw( -no_match_vars ); my $Worker = Parallel::PreForkManager->new({ 'ChildHandler' => \&WorkHandler, 'ParentCallback' => \&CallbackHandler, 'ProgressCallback' => { 'Log' => \&LogCallback, }, 'ChildSetupHook' => \&ChildSetupHook, 'ChildTeardownHook' => \&ChildTeardownHook, 'ChildCount' => 10, 'JobsPerChild' => 10, }); for ( my $i=0;$i<300;$i++ ) { $Worker->AddJob({ 'Value' => $i }); } $Worker->RunJobs(); sub ChildSetupHook { my ( $Self ) = @_; return; } sub ChildTeardownHook { my ( $Self ) = @_; return; } sub LogCallback { my ( $Self, $Data ) = @_; print "$PID LogCallback: $Data\n"; return; } sub WorkHandler { my ( $Self, $Thing ) = @_; my $Val = $Thing->{'Value'}; $Self->ProgressCallback( 'Log', "WORKER $PID - $Val" ); return { 'Data' => "Printed $Val in $PID" }; } sub CallbackHandler { my ( $Self, $Result ) = @_; my $Foo = $Result->{ 'Data' }; print "Child returned $Foo to Parent\n"; return; }; CONSTRUCTOR new( $Args ) my $Worker = Parellel::PreForkManager->new({ 'ChildHandler' => \&WorkHandler, 'ParentCallback' => \&CallbackHandler, 'ProgressCallback' => { 'Log' => \&LogCallback, }, 'ChildCount' => 10, 'JobsPerChild' => 10, }); ChildHandler The method which will do the work in the child. ParentCallback An optional method called in the parent process with the results from each child process. ProgressCallback An optional hashref of named methods which child processes may call back to the parent process and run. ChildCount Number of child processes to spawn/maintain, default 10. JobsPerChild The number of jobs a child process may run before it is respawned. Timeout Time limit in seconds for a child process run. WaitComplete Wait for all children to complete before returning? Defaults to 1. Call the WaitComplete() method to wait for children manually. ChildSetupHook Method which runs in the child when it is spawned. ChildTeardownHook Method which runs in the child when it is reaped. PUBLIC METHODS AddJob( $Job ) Adds a job to the job queue. A job is a reference (usually a hashref) which is passed to the child worker process for processing. RunJobs Start the children and run the jobs. GetResult Called in the parent callback, get a full results dataset from the child. WaitComplete Run in the parent process, waits for all children to complete. ProgressCallback USER DEFINED METHODS ChildHandler( $Job ) Passed to the constructor in the ChildHandler element. This method runs in each child to process the job queue. Its return value is optionally passed back to the parent via the defined ParentCallback method. ParentCallback( $Data ) Passed to the constructor in the ParentCallback element. This method runs in the parent after each job completion in the child. The $Data is passed back from the completed child to the parent. ProgressCallback( $Data ) Passed to the constructor in a named element in the ProgressCallback hashred element. These methods run in the parent, and are called from a running child by using the ProgressCallback method and given method name from within the child. The child may pass data back to the parent, and the results of the parent call are passed back to the running child. The parent is blocked from doing any scheduling work while this callback is running. This should only be used for short running tasks which need to run in the parent process. INTERNAL METHODS StartChildren Start the right number of child processes. StartChild Start a single child process. Child Child process main processing loop. Receive IPC Receive. Send IPC Send. JSON Note: All communication between the parent and a child are serialised using JSON.pm, please be aware of the data type restrictions of JSON serialisation. DEPENDENCIES Carp IO::Handle IO::Select JSON English BUGS Please report bugs via the github tracker. https://github.com/marcbradshaw/Parallel-PreForkManager/issues REFERENCE Obligatory XKCD reference. https://xkcd.com/927/ AUTHORS Marc Bradshaw, COPYRIGHT Copyright (c) 2018, Marc Bradshaw. CREDITS Originally based on code from Parallel::Fork::BossWorker by Jeff Rodriguez, (c) 2007 and Tim Wilde, (c) 2011 LICENCE This library is free software; you may redistribute it and/or modify it under the same terms as Perl itself.