[Catalyst] [RFC] C::P::Scheduler - cron-like scheduling of events

[Andrew Bramble]

I agree with the idea in principle , until a angry webmaster chops your 
fingers off for sneaking cron type execution into a web app.

Call me backwards , might this approach also support being  a harness for 
'real'  cron jobs.

IE

__PACKAGE__->schedule( 
	trigger=>'remove sessions',
	action=>'some forward or action to run'
);

then in a cron

#!perl
use MyApp
MyApp->schedule->trigger( 'remove sessions');



On Monday 12 December 2005 15:01, Andy Grundman wrote:
> I have a need for a simple scheduling plugin to do things like clean up
> database sessions, so I roughed out docs for a new plugin called Scheduler.
>  If you've got any thoughts or suggestions, please let me know. :)
>
> -Andy
>
> =head1 NAME
>
> Catalyst::Plugin::Scheduler - Schedule events to run in a cron-like fashion
>
> =head1 SYNOPSIS
>
>      use Catalyst qw/Scheduler/;
>
>      # enable logging
>      __PACKAGE__->config->{scheduler}->{logging} = 1;
>
>      # run remove_sessions in the Cron controller every hour
>      __PACKAGE__->schedule(
>          at    => '0 * * * *',
>          event => '/cron/remove_sessions'
>      );
>
>      # Run a coderef at 4:05am every Sunday
>      __PACKAGE__->schedule(
>          at    => '5 4 * * sun',
>          event => \&do_stuff,
>      );
>
> =head1 DESCRIPTION
>
> This plugin allows you to schedule events to run at recurring intervals.
> Events will run during the first request which meets or exceeds the
> specified time.  Depending on the level of traffic to the application,
> events may or may not run at exactly the correct time, but it should be
> enough to satisfy many basic scheduling needs.
>
> =head1 CONFIGURATION
>
> Configuration is optional and is specified in MyApp->config->{scheduler}.
>
> =head2 logging
>
> Set to 1 to enable logging of events as they are executed.  This option is
> enabled by default when running under -Debug mode.
>
> =head2 state_file
>
> The current state of every event is stored in a file.  By default this is
> $APP_HOME/scheduler.state.  If this file cannot be read or created at
> startup, your app will die.
>
> =head1 SCHEDULING
>
> Events are scheduled by calling the class method C<schedule> with two
> parameters: C<at> and C<event>.
>
> =head2 at
>
> The time to run an event is specified using crontab(5)-style syntax.
>
>      5 0 * * *      # 5 minutes after midnight, every day
>      15 14 1 * *    # run at 2:15pm on the first of every month
>      0 22 * * 1-5   # run at 10 pm on weekdays
>      5 4 * * sun    # run at 4:05am every Sunday
>
>  From crontab(5):
>
>      field          allowed values
>      -----          --------------
>      minute         0-59
>      hour           0-23
>      day of month   1-31
>      month          0-12 (or names, see below)
>      day of week    0-7 (0 or 7 is Sun, or use names)
>
> Instead of the first five fields, one of eight special strings may appear:
>
>      string         meaning
>      ------         -------
>      @reboot        Run once, at startup.
>      @yearly        Run once a year, "0 0 1 1 *".
>      @annually      (same as @yearly)
>      @monthly       Run once a month, "0 0 1 * *".
>      @weekly        Run once a week, "0 0 * * 0".
>      @daily         Run once a day, "0 0 * * *".
>      @midnight      (same as @daily)
>      @hourly        Run once an hour, "0 * * * *".
>
> =head2 event
>
> The event to run at the specified time can be either a Catalyst private
> action path or a coderef.  Both types of event methods will receive the $c
> object from the current request, but you must not rely on any request-
> specific information present in $c as it will be from a random user request
> at or near the event's specified run time.
>
> =head1 CAVEATS
>
> The time at which an event will run is determined completely by the
> requests made to the application.  Apps with heavy traffic may have events
> run at very close to the correct time, whereas apps with low levels of
> traffic may see events running much later than scheduled.  If this is a
> problem, you are encouraged to use a real cron scheduler.
>
> Events which consume a lot of time will slow the request processing for the
> user who triggers the event.  Long-running tasks should not be scheduled
> using this plugin.
>
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