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 managerDESCRIPTION
Padre uses threads for asynchroneous 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.
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
-
TODO: This is disabled for now since we need Wx 0.89 for stable threading.
Disable for profiling runs. In the degraded, threadless 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
Stops 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 regulary cleanup runs.
use_threads
Returns whether running in degraded mode (no threads, false) or normal operation (threads, true).
workers
Returns a list of the worker threads.
EVENT HANDLERS
on_close
Registered to be executed on editor shutdown. Executes the cleanup method.
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.
TODO
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.
SEE ALSO
The base class of all "work units" is Padre::Task.
AUTHOR
Steffen Mueller smueller@cpan.org
COPYRIGHT AND LICENSE
Copyright 2008 Gabor Szabo.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl 5 itself.