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 :

• github.com/javan/whenever

• github.com/yakischloba/em-timers

• github.com/adamwiggins/clockwork

More like complements :

• github.com/mojombo/chronic

• github.com/hpoydar/chronic_duration

installation¶ ↑

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')

which might be helpful when tracking threads.

Note that if there is an EventMachine present and running,

scheduler = Rufus::Scheduler.start_new

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

a note about cron jobs¶ ↑

This is a classical cron :

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

Rufus-scheduler supports two variants to that notation : seconds and timezones.

scheduler.cron '13 0 22 * * 1-5' do
  # every day of the week at 22:00:13
end

scheduler.cron '0 22 * * 1-5 Europe/Paris' do
  # every day of the week when it's 22:00 in Paris
end
scheduler.cron '0 22 * * 1-5 Etc/GMT+2' do
  # every day of the week when it's 22:00 in GMT+2
end

The timezones are the ones supported by the ‘tzinfo’ rubygem (tzinfo.rubyforge.org/).

The timezone support was contributed by Tanzeeb Khalili.

Since 2.0.9, “monthdays” are supported

scheduler.cron '0 22 * * sun#1,sun#2' do
  # every first and second sunday of the month, at 22:00
end

scheduler.join¶ ↑

Note that if you have a tiny script like this one :

require 'rubygems'; require 'rufus-scheduler'

scheduler = Rufus::Scheduler.start_new

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

And you run it, it will exit immediately.

If you place

scheduler.join

at the end, it will make the current (main) thread join the scheduler and prevent the Ruby runtime from exiting.

You shouldn’t be exposed to this issue when using EventMachine, since while running EM, your runtime won’t exit.

important note about #join¶ ↑

DO NOT CALL this #join method if you’re running rufus-scheduler from Rails or Sinatra or any application that’s already some kind of ‘daemon’. It’s not necessary! #join is meant for small standalone scripts.

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 :

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 => true¶ ↑

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 will come in 22 minutes instead of 21.

Warning, ‘cron’ behaves a bit differently than ‘in’ and ‘at’, if the scheduler is blocked working on a task, it may skip crons (while ins and ats get scheduled after).

scheduler.cron '0 16 * * * *' do
  puts "four o'clock tea"
end

If at 4pm the scheduler is in a blocking task, there will be no four o’clock tea.

:mutex => ‘that_mutex’¶ ↑

:blocking is nice but it is blocking the whole scheduler. What about something more fine-grained ? And also something that can be used with in, at, every and cron ?

scheduler.in '20m', :mutex => 'that_mutex' do
  puts "order ristretto"
  sleep 2 * 60
  puts "ah, that was delicious"
end
scheduler.in '21m' :mutex => 'that_mutex' do
  puts "order espresso"
end

the “order espresso” will only get triggered once the ristretto has been consumed. Rufus-scheduler will create a ‘that_mutex’ mutex and keep track of it. Don’t go on passing too many different mutex names, rufus-scheduler will keep track of each of them (they won’t get garbage collected).

It’s OK to use a mutex directly:

m = Mutex.new
# ...
scheduler.cron  '0 18 * * *', :mutex => m do
  # ...
end
scheduler.in '21m' :mutex => m do
  # ...
end

It can be handy for even more fine-grained control:

m = Mutex.new
# ...
scheduler.cron  '0 18 * * *', :mutex => m do
  # ...
end
scheduler.in '21m' do
  # non-critical
  m.synchronize do
    # critical
  end
  # non-critical
end

:allow_overlapping => false¶ ↑

By default, every and cron jobs will “overlap”:

scheduler.every '3s' do
  4.times do |i|
    puts "hello #{i}"
    sleep 1
  end
end

You might end up with something that looks like

hello 0
hello 1
hello 2
hello 3
hello 3
hello 4
...

This every job will have overlaps. To prevent that:

scheduler.every '3s', :allow_overlapping => false do
  # ...
end

‘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 (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

Note : setting a :first_at/:first_in in the past will get rufus-scheduler to trigger for all the past schedules until now. Adding :discard_past => true will prevent this.

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.

#running?¶ ↑

job = scheduler.every '3d' do
  # ...
end

# ...

p job.running?

Job#running? will return true when the job got triggered and is actually performing.

Please note, that #running? is not related to the #paused? which is detailed in the next section.

#pause, #resume and #paused?¶ ↑

Jobs, as well as the scheduler itself have a pair of #pause and #resume methods.

job = scheduler.every '2h' do
  # ...
end

# ...

job.pause # the job will be scheduled but won't trigger

# ...

puts job.paused?

Pausing / resuming a job doesn’t affect the scheduling of a job, it merely “silences” it, its block won’t get executed. Calling resume will not reset the schedule of the job. If you schedule a job to trigger every 10 minutes at 10am and pause it from 1020 to 1025, it’s next triggering time will be 1030 approximately.

One can pause an “at” or “in” job. If it’s still paused at trigger time, it will simply become a dud.

As said, the scheduler has a #pause(job_or_job_id) and a #resume(job_or_job_id) pair of methods:

scheduler.pause(job)
scheduler.pause(job_id)
scheduler.resume(job)
scheduler.resume(job_id)

Scheduler#running_jobs¶ ↑

One can get a list of the jobs just triggered (actually running) by doing

jobs = scheduler.running_jobs

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’.

For compatibility with older (1.x) versions, schedulables with a trigger methods are accepted :

class JobThing
  def trigger(params)
    job = params[:job]
  end
end

The ‘params’ correspond to the scheduler job params, and the key :job points to the rufus-scheduler job for the schedulable that is passed to a ‘call 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 exceptions occur when a job performs, the error messages 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

These are OK too:

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

# or

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

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 (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
}

with Passenger¶ ↑

“it terminates for no apparent reason !”

github.com/jmettraux/rufus-scheduler/issues/issue/10

tested with¶ ↑

• 1.8.7-p249

• 1.9.2-p290

• jruby-1.5.1

on Mac OS X (Snow Leopard).

dependencies¶ ↑

The ‘tzinfo’ rubygem.

The ruby gem ‘eventmachine’ if you use Rufus::Scheduler::EmScheduler, else no other dependencies.

mailing list¶ ↑

On the rufus-ruby list :

groups.google.com/group/rufus-ruby

issue tracker¶ ↑

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

irc¶ ↑

irc.freenode.net #ruote

source¶ ↑

github.com/jmettraux/rufus-scheduler

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

credits¶ ↑

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

authors¶ ↑

John Mettraux, jmettraux@gmail.com, jmettraux.github.com

the rest of Rufus¶ ↑

rufus.rubyforge.org

license¶ ↑

MIT