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

[Adam Jacob]

Do you write this yourself, or use Schedule::Cron?

Adam

On Dec 11, 2005, at 8:01 PM, 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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