littledata:synced-cron
A simple cron system for Meteor. It supports syncronizing jobs between multiple processes. In other words, if you add a job that runs every hour and your deployment consists of multiple app servers, only one of the app servers will execute the job each time (whichever tries first).
Migrated from percolate:synced-cron littledata:synced-cron
Since the original creator of the project could no longer maintain it, we had to migrate the package to another organisation to allow further maintenance and updates.
To migrate you can simply run
$ meteor remove percolate:synced-cron && meteor add littledata:synced-cron
Installation
$ meteor add littledata:synced-cron
API
Basics
To write a cron job, give it a unique name, a schedule and a function to run like below. SyncedCron uses the fantastic later.js library behind the scenes. A Later.js parse
object is passed into the schedule call that gives you a huge amount of flexibility for scheduling your jobs, see the documentation.
SyncedCron.add({
name: 'Crunch some important numbers for the marketing department',
schedule: function(parser) {
// parser is a later.parse object
return parser.text('every 2 hours');
},
job: function() {
var numbersCrunched = CrushSomeNumbers();
return numbersCrunched;
}
});
To start processing your jobs, somewhere in your project add:
SyncedCron.start();
Advanced
SyncedCron uses a collection called cronHistory
to syncronize between processes. This also serves as a useful log of when jobs ran along with their output or error. A sample item looks like:
{ _id: 'wdYLPBZp5zzbwdfYj',
intendedAt: Sun Apr 13 2014 17:34:00 GMT-0700 (MST),
finishedAt: Sun Apr 13 2014 17:34:01 GMT-0700 (MST),
name: 'Crunch some important numbers for the marketing department',
startedAt: Sun Apr 13 2014 17:34:00 GMT-0700 (MST),
result: '1982 numbers crunched'
}
Call SyncedCron.nextScheduledAtDate(jobName)
to find the date that the job
referenced by jobName
will run next.
Call SyncedCron.remove(jobName)
to remove and stop running the job referenced by jobName.
Call SyncedCron.stop()
to remove and stop all jobs.
Call SyncedCron.pause()
to stop all jobs without removing them. The existing jobs can be rescheduled (i.e. restarted) with SyncedCron.start()
.
To schedule a once off (i.e not recurring) event, create a job with a schedule like this parser.recur().on(date).fullDate();
Configuration
You can configure SyncedCron with the config
method. Defaults are:
SyncedCron.config({
// Log job run details to console
log: true,
// Use a custom logger function (defaults to Meteor's logging package)
logger: null,
// Name of collection to use for synchronisation and logging
collectionName: 'cronHistory',
// Default to using localTime
utc: false,
/*
TTL in seconds for history records in collection to expire
NOTE: Unset to remove expiry but ensure you remove the index from
mongo by hand
ALSO: SyncedCron can't use the `_ensureIndex` command to modify
the TTL index. The best way to modify the default value of
`collectionTTL` is to remove the index by hand (in the mongo shell
run `db.cronHistory.dropIndex({startedAt: 1})`) and re-run your
project. SyncedCron will recreate the index with the updated TTL.
*/
collectionTTL: 172800
});
Logging
SyncedCron uses Meteor's logging
package by default. If you want to use your own logger (for sending to other consumers or similar) you can do so by configuring the logger
option.
SyncedCron expects a function as logger
, and will pass arguments to it for you to take action on.
var MyLogger = function(opts) {
console.log('Level', opts.level);
console.log('Message', opts.message);
console.log('Tag', opts.tag);
}
SyncedCron.config({
logger: MyLogger
});
SyncedCron.add({ name: 'Test Job', ... });
SyncedCron.start();
The opts
object passed to MyLogger
above includes level
, message
, and tag
.
level
will be one ofinfo
,warn
,error
,debug
.message
is something likeScheduled "Test Job" next run @Fri Mar 13 2015 10:15:00 GMT+0100 (CET)
.tag
will always be"SyncedCron"
(handy for filtering).
Caveats
Beware, SyncedCron probably won't work as expected on certain shared hosting providers that shutdown app instances when they aren't receiving requests (like Heroku's free dyno tier or Meteor free galaxy).
Contributing
Write some code. Write some tests. To run the tests, do:
$ meteor test-packages ./
License
MIT. (c) Percolate Studio, originally designed and built by Zoltan Olah (@zol), now community maintained.
Synced Cron was developed as part of the Verso project.