= rufus-scheduler

rufus-scheduler is a Ruby gem for scheduling pieces of code (jobs). It understands running a job AT a certain time, IN a certain time, EVERY x time or simply via a CRON statement.

rufus-scheduler is no replacement for cron/at since it runs inside of Ruby.


== alternatives / complements

A list of related Ruby projects :

http://github.com/javan/whenever
http://github.com/yakischloba/em-timers/

More like complements :

http://github.com/mojombo/chronic/
http://github.com/hpoydar/chronic_duration


== installation

  sudo gem install rufus-scheduler


== usage

The usage is similar to the one of the old rufus-scheduler. There are a few differences though.

  require 'rubygems'
  require 'rufus/scheduler'

  scheduler = Rufus::Scheduler.start_new

  scheduler.in '20m' do
    puts "order ristretto"
  end

  scheduler.at 'Thu Mar 26 07:31:43 +0900 2009' do
    puts 'order pizza'
  end

  scheduler.cron '0 22 * * 1-5' do
    # every day of the week at 22:00 (10pm)
    puts 'activate security system'
  end

  scheduler.every '5m' do
    puts 'check blood pressure'
  end


This code summons a plain version of the scheduler, this can be made more explicit via :

  scheduler = Rufus::Scheduler::PlainScheduler.start_new

This PlainScheduler accepts a :thread_name option :

  scheduler = Rufus::Scheduler::PlainScheduler.start_new(:thread_name => 'my scheduler')

might be helpful when tracking threads.


Note that is there is EventMachine present and running,

  scheduler = Rufus::Scheduler.start_new

will return an instance of Rufus::Scheduler::EmScheduler (leveraging EventMachine).


== block parameters

Scheduled blocks accept 0 or 1 parameter (this unique parameter is the job
instance itself).

  scheduler.every '5m' do
    puts 'check blood pressure'
  end
  scheduler.every '1y' do |job|
    puts "check cholesterol levels (#{job.job_id})"
  end

See the class Job for more details :

http://rufus.rubyforge.org/rufus-scheduler/classes/Rufus/Scheduler/Job.html


== the time strings understood by rufus-scheduler

  require 'rubygems'
  require 'rufus/scheduler'

  p Rufus.parse_time_string '500'      # => 0.5
  p Rufus.parse_time_string '1000'     # => 1.0
  p Rufus.parse_time_string '1h'       # => 3600.0
  p Rufus.parse_time_string '1h10s'    # => 3610.0
  p Rufus.parse_time_string '1w2d'     # => 777600.0

  p Rufus.to_time_string 60              # => "1m"
  p Rufus.to_time_string 3661            # => "1h1m1s"
  p Rufus.to_time_string 7 * 24 * 3600   # => "1w"


== :blocking

Jobs will, by default, trigger in their own thread. This is usually desirable since one expects the scheduler to continue scheduling even if a job is currently running.

Jobs scheduled with the :blocking parameter will run in the thread of the scheduler, blocking it.

  scheduler.in '20m', :blocking => true do
    puts "order ristretto"
    sleep 2 * 60
  end
  scheduler.in '21m' do
    puts "order espresso"
  end

Hence, our espresso wil come in 22 minutes instead of 21.


== 'every' jobs and :first_at / :first_in

This job will execute every 3 days, but first time will be in 5 days from now :

  scheduler.every '3d', :first_in => '5d' do
    # do something
  end

This job will execute every 3 days, starting from Christmas Eve at noon :

  scheduler.every '3d', :first_at => '2009/12/24 12:00' do
    # do something
  end

The chronic gem may help (http://chronic.rubyforge.org/) :

  require 'chronic' # sudo gem install chronic

  scheduler.every '3h', :first_at => Chronic.parse('this tuesday 5:00') do
    # do something starting this tueday
  end


== self unschedule for 'cron' and 'every' jobs

'at' and 'in' jobs fire once only. 'cron' and 'every' jobs do fire repeatedly, so it might be useful to stop them.

  scheduler.every '3d' do |job|
    l = determine_crop_maturity_level()
    if l >= 7
      puts "crop is ready."
      job.unschedule
    else
      puts "crop not yet ready..."
    end
  end

In this example, the 'every' job will unschedule itself when the crop is ready.


== schedulables

Sometimes passing a block isn't that convenient :

  class JobThing
    def initialize (relevant_info)
      @ri = relevant_info
    end
    def call (job)
      do_something_about_it
    end
  end

  # ...

  scheduler.in '3d', JobThing.new('http://news.example.com/data_xyz')
  scheduler.in '1w', JobThing.new('http://news.example.com/data_abc'), :timeout => '1d'

rufus-scheduler accepts anything that responds to a call method with a unique parameter (it will pass the job) as a 'schedulable'.


== looking up jobs

  scheduler.jobs
    # returns a map job_id => job of at/in/every jobs

  scheduler.cron_jobs
    # idem for cron jobs

  scheduler.all_jobs
    # idem but for every/at/in/cron jobs (all of them)

  scheduler.find_by_tag(t)
    # returns all the jobs with a given tag (passed at schedule time with :tags)


== unscheduling jobs

The 'scheduling' methods always return an instance of Rufus::Scheduler::Job. This object can be used for unscheduling :

  job = scheduler.in '2d', :tags => 'admin' do
    run_backlog_cleaning()
  end

  # later ...

  job.unschedule
    # or
  scheduler.unschedule(job.job_id)


== tags

You can specify tags at schedule time :

  scheduler.in '2d', :tags => 'admin' do
    run_backlog_cleaning()
  end
  scheduler.every '3m', :tags => 'production' do
    check_order_log()
  end

And later query the scheduler for those jobs :

  admin_jobs = scheduler.find_by_tag('admin')
  production_jobs = scheduler.find_by_tag('production')


== timeout

One can specify a timeout for the triggering of a job.

  scheduler.every '2d', :timeout => '40m' do
    begin
      run_backlog_cleaning()
    rescue Rufus::Scheduler::TimeOutError => toe
      # timeout occurred
    end
  end

This job will run every two days. If a run takes more than 40 minutes it will timeout (its thread will receive a TimeOutError).

This timeout feature relies on an 'in' job scheduled at the moment the main job gets triggered, hence the '40m' time string format.


== exceptions in jobs

By default, when exception occur when a job performs, the error message will be output to the STDOUT.

It's easy to customize that behaviour :

  scheduler = Rufus::Scheduler::PlainScheduler.start_new
    # or
  #scheduler = Rufus::Scheduler::EmScheduler.start_new

  def scheduler.handle_exception (job, exception)
    puts "job #{job.job_id} caught exception '#{exception}'"
  end

For backward compatibility, overriding #log_exception is still OK :

  def scheduler.log_exception (exception)
    puts "caught exception '#{exception}'"
  end

Note that an every job or a cron job will stay scheduled even if it experiences an exception.


== frequency

The default frequency for the scheduler is 0.330 seconds. This means that the usual scheduler implementation will wake up, trigger jobs that are to be triggered and then go back to sleep for 0.330 seconds. Note that this doesn't mean that the scheduler will wake up very 0.330 seconds (checking and triggering do take time).

You can set a different frequency when starting / initializing the scheduler :

  require 'rubygems'
  require 'rufus/scheduler'

  scheduler = Rufus::Scheduler.start_new(:frequency => 60.0)
    # for a lazy scheduler that only wakes up every 60 seconds


== usage with EventMachine

rufus-scheduler 2.0 can be used in conjunction with EventMachine (http://github.com/eventmachine/eventmachine/).

More and more ruby applications are using EventMachine. This flavour of the scheduler relies on EventMachine, thus it doesn't require a separate thread like the PlainScheduler does.

  require 'rubygems'
  require 'eventmachine'

  EM.run {

    scheduler = Rufus::Scheduler::EmScheduler.start_new

    scheduler.in '20m' do
      puts "order ristretto"
    end
  }


== tested with

ruby 1.8.6, ruby 1.9.1p0
on jruby 1.2.0 it has some tiny issues (spec/blocking_spec.rb)


== dependencies

the ruby gem 'eventmachine' if you use Rufus::Scheduler::EmScheduler, else no other dependencies.


== mailing list

On the rufus-ruby list :

http://groups.google.com/group/rufus-ruby


== issue tracker

http://rubyforge.org/tracker/?atid=18584&group_id=4812&func=browse


== irc

  irc.freenode.net #ruote


== source

http://github.com/jmettraux/rufus-scheduler

  git clone git://github.com/jmettraux/rufus-scheduler.git


== credits

http://github.com/jmettraux/rufus-scheduler/blob/master/CREDITS.txt


== authors

John Mettraux, jmettraux@gmail.com, http://jmettraux.wordpress.com


== the rest of Rufus

http://rufus.rubyforge.org


== license

MIT