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semuel edited this page Mar 13, 2012 · 4 revisions

Adding Scheduled Tasks

Inside the MT installation, there is “$MT_DIR/tools/run-periodic-tasks”, that, well, run the periodic tasks. These do a lot of useful things, like delete old sessions.

But before we show how to add a periodic task to your plugin, we will start with warnings:
Do not make your plugin depend on the periodic tasks. A lot of sites does not run them at all.
If your plugin have to have these tasks running, please write in clearly in the documentation. (that nobody reads, btw)

Now that we are clear on the subject, lets start.

What are periodic tasks?

The default periodic tasks are:

  • Publish scheduled entries in the designated time
  • Building templates that are marked “Publish by queue” in the background
  • Delete spam comments and trackbacks
  • Delete temporary files
  • Delete expired sessions

For all this to happen, you need to do any of the following:

  • Run “$MT_DIR/tools/run-periodic-tasks” manually from the command line on regular basis
  • Set a cron (on Linux) or a task scheduler (on Windows) to run this on regular basis
  • Get the log feed on regular basis
  • Use the XML-RPC API to run them, using mt.runPeriodicTasks

Example

Specification

  1. Run every two minutes
  2. The task will just add “run scheduled tasks” line to the log

config.yaml

id: MyPlugin10
key: MyPlugin10
name: <__trans phrase="Sample Plugin Scheduled Tasks">
version: 1.1
description: <__trans phrase="_PLUGIN_DESCRIPTION">
author_name: <__trans phrase="_PLUGIN_AUTHOR">
author_link: http://www.example.com/about/
doc_link: http://www.example.com/docs/
l10n_class: MyPlugin10::L10N

tasks:
    MyCustomTask:
        label: Do something every two minutes
        frequency: 120
        code: $MyPlugin10::MyPlugin10::Tasks::do_task

Commentary

  • tasks
    • This is the registry top for tasks
  • MyCustomTask
    • The name of the task to add
  • label
    • Description of the task
  • frequency
    • Task starting interval (in seconds)
  • code
    • The function to run, in the standard MT handler format
    • $Plugin-name :: Perl Module :: handler name

Tasks.pm

package MyPlugin10::Tasks;
use strict;

sub do_task {
    doLog("run scheduled tasks");
}

sub doLog {
    my ($msg, $class) = @_;
    return unless defined($msg);

    require MT::Log;
    my $log = new MT::Log;
    $log->message($msg);
    $log->level(MT::Log::DEBUG());
    $log->class($class) if $class;
    $log->save or die $log->errstr;
}

1;

Commentary

Running the task

We will use our trusty super-computer (that now got a little time off from calculating all these file names) to show how to run these tasks. Apparently, this computer have Linux running

$ cd $MT_DIR
$ sudo -u apache ./tools/run-periodic-tasks
$ sudo -u apache ./tools/run-periodic-tasks

Commentary

  • The periodic tasks should run under the same user/permissions as the webserver. In this example we use the apache user, (using the sudo -u command) but please adjust it to your environment (common cases: www-data, SuExec)
  • We just ran the run-periodic-tasks twice, without waiting

Results

  • Go to System => Tools => Log, and if there are too many logs, (Warning: Playing with the production server is bad for your sleeping hours) filter the level to show only debug messages
  • You should see the “run scheduled tasks” message only once

There is only one message because we run the second command immidiately after the first, while the task is set to run only every two minutes.
If you will wait two minutes and then run it again, another message line will be added

Summery

Periodic tasks are a useful tool for doing time-based operations. For example, closing comments and trackbacks for old entries.

Still, for these to work, the periodic task script should be run on regular basis.

Plugin Download

MyPlugin10.zip(2.25KB)

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