NAME
Catalyst::Plugin::Scheduler - Schedule events to run in a cron-like
fashion
SYNOPSIS
use Catalyst qw/Scheduler/;
# run remove_sessions in the Cron controller every hour
__PACKAGE__->schedule(
at => '0 * * * *',
event => '/cron/remove_sessions'
);
# Run a subroutine at 4:05am every Sunday
__PACKAGE__->schedule(
at => '5 4 * * sun',
event => \&do_stuff,
);
# A long-running scheduled event that must be triggered
# manually by an authorized user
__PACKAGE__->schedule(
trigger => 'rebuild_search_index',
event => '/cron/rebuild_search_index',
);
$ wget -q http://www.myapp.com/?schedule_trigger=rebuild_search_index
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.
CONFIGURATION
Configuration is optional and is specified in
MyApp->config->{scheduler}.
logging
Set to 1 to enable logging of events as they are executed. This option
is enabled by default when running under -Debug mode. Errors are always
logged regardless of the value of this option.
time_zone
The time zone of your system. This will be autodetected where possible,
or will default to UTC (GMT). You can override the detection by
providing a valid DateTime time zone string, such as 'America/New_York'.
state_file
The current state of every event is stored in a file. By default this is
$APP_HOME/scheduler.state. This file is created on the first request if
it does not already exist.
yaml_file
The location of the optional YAML event configuration file. By default
this is $APP_HOME/scheduler.yml.
hosts_allow
This option specifies IP addresses for trusted users. This option
defaults to 127.0.0.1. Multiple addresses can be specified by using an
array reference. This option is used for both events where auto_run is
set to 0 and for manually-triggered events.
__PACKAGE__->config->{scheduler}->{hosts_allow} = '192.168.1.1';
__PACKAGE__->config->{scheduler}->{hosts_allow} = [
'127.0.0.1',
'192.168.1.1'
];
SCHEDULING
AUTOMATED EVENTS
Events are scheduled by calling the class method "schedule".
MyApp->schedule(
at => '0 * * * *',
event => '/cron/remove_sessions',
);
package MyApp::Controller::Cron;
sub remove_sessions : Private {
my ( $self, $c ) = @_;
$c->delete_expired_sessions;
}
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 seven special strings may
appear:
string meaning
------ -------
@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 * * * *".
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.
Important: Methods used for events should be marked "Private" so that
they can not be executed via the browser.
auto_run
The auto_run parameter specifies when the event is allowed to be
executed. By default this option is set to 1, so the event will be
executed during the first request that matches the specified time in
"at".
If set to 0, the event will only run when a request is made by a user
from an authorized address. The purpose of this option is to allow
long-running tasks to execute only for certain users.
MyApp->schedule(
at => '0 0 * * *',
event => '/cron/rebuild_search_index',
auto_run => 0,
);
package MyApp::Controller::Cron;
sub rebuild_search_index : Private {
my ( $self, $c ) = @_;
# rebuild the search index, this may take a long time
}
Now, the search index will only be rebuilt when a request is made from a
user whose IP address matches the list in the "hosts_allow" config
option. To run this event, you probably want to ping the app from a cron
job.
0 0 * * * wget -q http://www.myapp.com/
MANUAL EVENTS
To create an event that does not run on a set schedule and must be
manually triggered, you can specify the "trigger" option instead of
"at".
__PACKAGE__->schedule(
trigger => 'send_email',
event => '/events/send_email',
);
The event may then be triggered by a standard web request from an
authorized user. The trigger to run is specified by using a special GET
parameter, 'schedule_trigger'; the path requested does not matter.
http://www.myapp.com/?schedule_trigger=send_email
By default, manual events may only be triggered by requests made from
localhost (127.0.0.1). To allow other addresses to run events, use the
configuration option "hosts_allow".
SCHEDULING USING A YAML FILE
As an alternative to using the schedule() method, you may define
scheduled events in an external YAML file. By default, the plugin looks
for the existence of a file called "scheduler.yml" in your application's
home directory. You can change the filename using the configuration
option "yaml_file".
Modifications to this file will be re-read once per minute during the
normal event checking process.
Here's an example YAML configuration file with 4 events. Each event is
denoted with a '-' character, followed by the same parameters used by
the "schedule" method. Note that coderef events are not supported by the
YAML file.
---
- at: '* * * * *'
event: /cron/delete_sessions
- event: /cron/send_email
trigger: send_email
- at: '@hourly'
event: /cron/hourly
- at: 0 0 * * *
auto_run: 0
event: /cron/rebuild_search_index
SECURITY
All events are run inside of an eval container. This protects the user
from receiving any error messages or page crashes if an event fails to
run properly. All event errors are logged, even if logging is disabled.
PLUGIN SUPPORT
Other plugins may register scheduled events if they need to perform
periodic maintenance. Plugin authors, be sure to inform your users if
you do this! Events should be registered from a plugin's "setup" method.
sub setup {
my $c = shift;
$c->maybe::next::method(@_);
if ( $c->can('schedule') ) {
$c->schedule(
at => '0 * * * *',
event => \&cleanup,
);
}
}
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 can use a real cron entry that simply hits your
application at the desired time.
0 * * * * wget -q http://www.myapp.com/
Events which consume a lot of time will slow the request processing for
the user who triggers the event. For these types of events, you should
use auto_run => 0 or manual event triggering.
PERFORMANCE
The plugin only checks once per minute if any events need to be run, so
the overhead on each request is minimal. On my test server, the
difference between running with Scheduler and without was only around
0.02% (0.004 seconds).
Of course, when a scheduled event runs, performance will depend on
what's being run in the event.
METHODS
schedule
Schedule is a class method for adding scheduled events. See the
"SCHEDULING"" in " section for more information.
scheduler_state
The current state of all scheduled events is available in an easy-to-use
format by calling $c->scheduler_state. You can use this data to build an
admin view into the scheduling engine, for example. This same data is
also displayed on the Catalyst debug screen.
This method returns an array reference containing a hash reference for
each event.
[
{
'last_run' => '2005-12-29 16:29:33 EST',
'auto_run' => 1,
'last_output' => 1,
'at' => '0 0 * * *',
'next_run' => '2005-12-30 00:00:00 EST',
'event' => '/cron/session_cleanup'
},
{
'auto_run' => 1,
'at' => '0 0 * * *',
'next_run' => '2005-12-30 00:00:00 EST',
'event' => '/cron/build_rss'
},
]
INTERNAL METHODS
The following methods are extended by this plugin.
dispatch
The main scheduling logic takes place during the dispatch phase.
dump_these
On the Catalyst debug screen, all scheduled events are displayed
along with the next time they will be executed.
setup
SEE ALSO
crontab(5)
AUTHOR
Andy Grundman, <andy@hybridized.org>
COPYRIGHT
This program is free software, you can redistribute it and/or modify it
under the same terms as Perl itself.