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Padre::TaskManager.3pm

NAME

Padre::TaskManager - Padre Background Task Scheduler

SYNOPSIS

   require Padre::Task::Foo;
   my $task = Padre::Task::Foo->new(some => 'data');
   $task->schedule; # handed off to the task manager
 
 

DESCRIPTION

Padre uses threads for asynchronous background operations which may take so long that they would make the GUI unresponsive if run in the main (GUI) thread.

This class implements a pool of a configurable number of re-usable worker threads. Re-using threads is necessary as the overhead of spawning threads is high. Additional threads are spawned if many background tasks are scheduled for execution. When the load goes down, the number of extra threads is (slowly!) reduced down to the default.

INTERFACE

Class Methods

"new"

The constructor returns a "Padre::TaskManager" object. At the moment, "Padre::TaskManager" is a singleton. An object is instantiated when the editor object is created.

Optional parameters:

min_no_workers / max_no_workers

Set the minimum and maximum number of worker threads to spawn. Default: 1 to 3

The first workers are spawned lazily: I.e. only when the first task is being scheduled.

use_threads

Disable for profiling runs. In the degraded, thread-less mode, all tasks are run in the main thread. Default: 1 (use threads)

reap_interval

The number of milliseconds to wait before checking for dead worker threads. Default: 15000ms

Instance Methods

"schedule"

Given a "Padre::Task" instance (or rather an instance of a subclass), schedule that task for execution in a worker thread. If you call the "schedule" method of the task object, it will proxy to this method for convenience.

"setup_workers"

Create more workers if necessary. Called by "reap" which is called regularly by the reap timer, so users don't typically need to call this.

"reap"

Check for worker threads that have exited and can be joined. If there are more worker threads than the normal number and they are idle, one worker thread (per "reap" call) is stopped.

This method is called regularly by the reap timer (see the "reap_interval" option to the constructor) and it's not typically called by users.

"cleanup"

Shutdown all services with a HANGUP, then stop all worker threads. Called on editor shutdown.

Accessors

"task_queue"

Returns the queue of tasks to be processed as a Thread::Queue object. The tasks in the queue have been serialized for passing between threads, so this is mostly useful internally or for checking the number of outstanding jobs.

"reap_interval"

Returns the number of milliseconds between the regular cleanup runs.

"use_threads"

Returns whether running in degraded mode (no threads, false) or normal operation (threads, true).

"running_tasks"

Returns the number of tasks that are currently being executed.

"shutdown_services"

Gracefully shutdown the services by instructing them to hangup themselves and return via the usual Task mechanism.

"workers"

Returns a list of the worker threads.

Event Handlers

"on_task_done_event"

This event handler is called when a background task has finished execution. It deserializes the background task object and calls its "finish" method with the Padre main window object as first argument. (This is done because "finish" most likely updates the GUI.)

"on_task_start_event"

This event handler is called when a background task is about to start execution. It simply increments the running task counter.

"on_service_poll_event"

"on_dump_running_tasks"

Called by the toolbar task-status button. Dumps the list of running tasks to the output panel.

TO DO

What if the computer can't keep up with the queued jobs? This needs some consideration and probably, the "schedule()" call needs to block once the queue is ``full''. However, it's not clear how this can work if the Wx "MainLoop" isn't reached for processing finish events.

Polling services aliveness in a useful way, something a "Wx::Taskmanager" might like to display. Ability to selectively kill tasks/services

SEE ALSO

The base class of all ``work units'' is Padre::Task.

AUTHOR

Steffen Mueller "smueller@cpan.org"

COPYRIGHT AND LICENSE

Copyright 2008-2010 The Padre development team as listed in Padre.pm.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl 5 itself.