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scheduler for Ruby (at, in, cron and every jobs)


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Job scheduler for Ruby (at, cron, in and every jobs).

Note: maybe are you looking for the README of rufus-scheduler 2.x?


require 'rufus-scheduler'

scheduler = '3s' do
  puts 'Hello... Rufus'

  # let the current thread join the scheduler thread

Various forms of scheduling are supported:

require 'rufus-scheduler'

scheduler =

# ... '10d' do
  # do something in 10 days
end '2030/12/12 23:30:00' do
  # do something at a given point in time

scheduler.every '3h' do
  # do something every 3 hours

scheduler.cron '5 0 * * *' do
  # do something every day, five minutes after midnight
  # (see "man 5 crontab" in your terminal)

# ...


Rufus-scheduler (out of the box) is an in-process, in-memory scheduler.

It does not persist your schedules. When the process is gone and the scheduler instance with it, the schedules are gone.

related and similar gems

  • whenever - let cron call back your Ruby code, trusted and reliable cron drives your schedule
  • clockwork - rufus-scheduler inspired gem
  • crono - an in-Rails cron scheduler

(please note: rufus-scheduler is not a cron replacement)

note about the 3.0 line

It's a complete rewrite of rufus-scheduler.

There is no EventMachine-based scheduler anymore.

I don't know what this Ruby thing is, where are my Rails?

Sir, I'll drive you right to the tracks.

Notable changes:

  • As said, no more EventMachine-based scheduler
  • scheduler.every('100') { will schedule every 100 seconds (previously, it would have been 0.1s). This aligns rufus-scheduler on Ruby's sleep(100)
  • The scheduler isn't catching the whole of Exception anymore, only StandardError
  • The error_handler is #on_error (instead of #on_exception), by default it now prints the details of the error to $stderr (used to be $stdout)
  • Rufus::Scheduler::TimeOutError renamed to Rufus::Scheduler::TimeoutError
  • Introduction of "interval" jobs. Whereas "every" jobs are like "every 10 minutes, do this", interval jobs are like "do that, then wait for 10 minutes, then do that again, and so on"
  • Introduction of a :lockfile => true/filename mechanism to prevent multiple schedulers from executing
  • "discard_past" is on by default. If the scheduler (its host) sleeps for 1 hour and a every '10m' job is on, it will trigger once at wakeup, not 6 times (discard_past was false by default in rufus-scheduler 2.x). No intention to re-introduce :discard_past => false in 3.0 for now.
  • Introduction of Scheduler #on_pre_trigger and #on_post_trigger callback points

getting help

So you need help. People can help you, but first help them help you, and don't waste their time. Provide a complete description of the issue. If it works on A but not on B and others have to ask you: "so what is different between A and B" you are wasting everyone's time.

"hello" and "thanks" are not swear words.

Go read how to report bugs effectively, twice.

Update: might help help you.

on StackOverflow

Use this form. It'll create a question flagged "rufus-scheduler" and "ruby".

Here are the questions tagged rufus-scheduler.

on IRC

I sometimes haunt #ruote on The channel is not dedicated to rufus-scheduler, so if you ask a question, first mention it's about rufus-scheduler.

Please note that I prefer helping over Stack Overflow because it's more searchable than the ruote IRC archive.


Yes, issues can be reported in rufus-scheduler issues, I'd actually prefer bugs in there. If there is nothing wrong with rufus-scheduler, a Stack Overflow question is better.



Rufus-scheduler supports five kinds of jobs. in, at, every, interval and cron jobs.

Most of the rufus-scheduler examples show block scheduling, but it's also OK to schedule handler instances or handler classes.

in, at, every, interval, cron

In and at jobs trigger once.

require 'rufus-scheduler'

scheduler = '10d' do
  puts "10 days reminder for review X!"
end '2014/12/24 2000' do
  puts "merry xmas!"

In jobs are scheduled with a time interval, they trigger after that time elapsed. At jobs are scheduled with a point in time, they trigger when that point in time is reached (better to choose a point in the future).

Every, interval and cron jobs trigger repeatedly.

require 'rufus-scheduler'

scheduler =

scheduler.every '3h' do
  puts "change the oil filter!"

scheduler.interval '2h' do
  puts "thinking..."
  puts sleep(rand * 1000)
  puts "thought."

scheduler.cron '00 09 * * *' do
  puts "it's 9am! good morning!"

Every jobs try hard to trigger following the frequency they were scheduled with.

Interval jobs, trigger, execute and then trigger again after the interval elapsed. (every jobs time between trigger times, interval jobs time between trigger termination and the next trigger start).

Cron jobs are based on the venerable cron utility (man 5 crontab). They trigger following a pattern given in (almost) the same language cron uses.

#schedule_x vs #x

schedule_in, schedule_at, schedule_cron, etc will return the new Job instance.

in, at, cron will return the new Job instance's id (a String).

job_id = '10d' do
    # ...
job = scheduler.job(job_id)

# versus

job =
  scheduler.schedule_in '10d' do
    # ...

# also

job = '10d', :job => true do
    # ...

#schedule and #repeat

Sometimes it pays to be less verbose.

The #schedule methods schedules an at, in or cron job. It just decide based on its input. It returns the Job instance.

scheduler.schedule '10d' do; end.class
  # => Rufus::Scheduler::InJob

scheduler.schedule '2013/12/12 12:30' do; end.class
  # => Rufus::Scheduler::AtJob

scheduler.schedule '* * * * *' do; end.class
  # => Rufus::Scheduler::CronJob

The #repeat method schedules and returns an EveryJob or a CronJob.

scheduler.repeat '10d' do; end.class
  # => Rufus::Scheduler::EveryJob

scheduler.repeat '* * * * *' do; end.class
  # => Rufus::Scheduler::CronJob

(Yes, no combination heres gives back an IntervalJob).

schedule blocks arguments (job, time)

A schedule block may be given 0, 1 or 2 arguments.

The first argument is "job", it's simple the Job instance involved. It might be useful if the job is to be unscheduled for some reason.

scheduler.every '10m' do |job|

  status = determine_pie_status

  if status == 'burnt' || status == 'cooked'

The second argument is "time", it's the time when the job got cleared for triggering (not

Note that time is the time when the job got cleared for triggering. If there are mutexes involved, now = mutex_wait_time + time...

"every" jobs and changing the next_time in-flight

It's OK to change the next_time of an every job in-flight:

scheduler.every '10m' do |job|

  # ...

  status = determine_pie_status

  job.next_time = + 30 * 60 if status == 'burnt'
    # if burnt, wait 30 minutes for the oven to cool a bit

It should work as well with cron jobs, not so with interval jobs whose next_time is computed after their block ends its current run.

scheduling handler instances

It's OK to pass any object, as long as it respond to #call(), when scheduling:

class Handler
  def, time)
    p "- Handler called for #{} at #{time}"
end '10d', Handler

# or

class OtherHandler
  def initialize(name)
    @name = name
  def call(job, time)
    p "* #{time} - Handler #{name.inspect} called for #{}"

oh ='Doe')

scheduler.every '10m', oh '3d5m', oh

The call method must accept 2 (job, time), 1 (job) or 0 arguments.

Note that time is the time when the job got cleared for triggering. If there are mutexes involved, now = mutex_wait_time + time...

scheduling handler classes

One can pass a handler class to rufus-scheduler when scheduling. Rufus will instantiate it and that instance will be available via job#handler.

class MyHandler
  attr_reader :count
  def initialize
    @count = 0
  def call(job)
    @count += 1
    puts ". #{self.class} called at #{} (#{@count})"

job = scheduler.schedule_every '35m', MyHandler

  # => #<MyHandler:0x000000021034f0>
  # => 0

If you want to keep that "block feeling":

job_id =
  scheduler.every '10m', do
    def call(job)
      puts ". hello #{self.inspect} at #{}"

pause and resume the scheduler

The scheduler can be paused via the #pause and #resume methods. One can determine if the scheduler is currently paused by calling #paused?.

While paused, the scheduler still accepts schedules, but no schedule will get triggered as long as #resume isn't called.

job options

:blocking => true

By default, jobs are triggered in their own, new thread. When :blocking => true, the job is triggered in the scheduler thread (a new thread is not created). Yes, while the job triggers, the scheduler is not scheduling.

:overlap => false

Since, by default, jobs are triggered in their own new thread, job instances might overlap. For example, a job that takes 10 minutes and is scheduled every 7 minutes will have overlaps.

To prevent overlap, one can set :overlap => false. Such a job will not trigger if one of its instance is already running.

:mutex => mutex_instance / mutex_name / array of mutexes

When a job with a mutex triggers, the job's block is executed with the mutex around it, preventing other jobs with the same mutex to enter (it makes the other jobs wait until it exits the mutex).

This is different from :overlap => false, which is, first, limited to instances of the same job, and, second, doesn't make the incoming job instance block/wait but give up.

:mutex accepts a mutex instance or a mutex name (String). It also accept an array of mutex names / mutex instances. It allows for complex relations between jobs.

Array of mutexes: original idea and implementation by Rainux Luo

Warning: creating lots of different mutexes is OK. Rufus-scheduler will place them in its Scheduler#mutexes hash... And they won't get garbage collected.

:timeout => duration or point in time

It's OK to specify a timeout when scheduling some work. After the time specified, it gets interrupted via a Rufus::Scheduler::TimeoutError. '10d', :timeout => '1d' do
    # ... do something
  rescue Rufus::Scheduler::TimeoutError
    # ... that something got interrupted after 1 day

The :timeout option accepts either a duration (like "1d" or "2w3d") or a point in time (like "2013/12/12 12:00").

:first_at, :first_in, :first, :first_time

This option is for repeat jobs (cron / every) only.

It's used to specify the first time after which the repeat job should trigger for the first time.

In the case of an "every" job, this will be the first time (modulo the scheduler frequency) the job triggers. For a "cron" job, it's the time after which the first schedule will trigger.

scheduler.every '2d', :first_at => + 10 * 3600 do
  # ... every two days, but start in 10 hours

scheduler.every '2d', :first_in => '10h' do
  # ... every two days, but start in 10 hours

scheduler.cron '00 14 * * *', :first_in => '3d' do
  # ... every day at 14h00, but start after 3 * 24 hours

:first, :first_at and :first_in all accept a point in time or a duration (number or time string). Use the symbol you think make your schedule more readable.

Note: it's OK to change the first_at (a Time instance) directly:

job.first_at = + 10
job.first_at = Rufus::Scheduler.parse('2029-12-12')

The first argument (in all its flavours) accepts a :now or :immediately value. That schedules the first occurence for immediate triggering. Consider:

require 'rufus-scheduler'

s =

n =; p [ :scheduled_at, n, n.to_f ]

s.every '3s', :first => :now do
  n =; p [ :in, n, n.to_f ]


that'll output something like:

[:scheduled_at, 2014-01-22 22:21:21 +0900, 1390396881.344438]
[:in, 2014-01-22 22:21:21 +0900, 1390396881.6453865]
[:in, 2014-01-22 22:21:24 +0900, 1390396884.648807]
[:in, 2014-01-22 22:21:27 +0900, 1390396887.651686]
[:in, 2014-01-22 22:21:30 +0900, 1390396890.6571937]

:last_at, :last_in, :last

This option is for repeat jobs (cron / every) only.

It indicates the point in time after which the job should unschedule itself.

scheduler.cron '5 23 * * *', :last_in => '10d' do
  # ... do something every evening at 23:05 for 10 days

scheduler.every '10m', :last_at => + 10 * 3600 do
  # ... do something every 10 minutes for 10 hours

scheduler.every '10m', :last_in => 10 * 3600 do
  # ... do something every 10 minutes for 10 hours

:last, :last_at and :last_in all accept a point in time or a duration (number or time string). Use the symbol you think make your schedule more readable.

Note: it's OK to change the last_at (nil or a Time instance) directly:

job.last_at = nil
  # remove the "last" bound

job.last_at = Rufus::Scheduler.parse('2029-12-12')
  # set the last bound

:times => nb of times (before auto-unscheduling)

One can tell how many times a repeat job (CronJob or EveryJob) is to execute before unscheduling by itself.

scheduler.every '2d', :times => 10 do
  # ... do something every two days, but not more than 10 times

scheduler.cron '0 23 * * *', :times => 31 do
  # ... do something every day at 23:00 but do it no more than 31 times

It's OK to assign nil to :times to make sure the repeat job is not limited. It's useful when the :times is determined at scheduling time.

scheduler.cron '0 23 * * *', :times => nolimit ? nil : 10 do
  # ...

The value set by :times is accessible in the job. It can be modified anytime.

job =
  scheduler.cron '0 23 * * *' do
    # ...

# later on...

job.times = 10
  # 10 days and it will be over

Job methods

When calling a schedule method, the id (String) of the job is returned. Longer schedule methods return Job instances directly. Calling the shorter schedule methods with the :job => true also return Job instances instead of Job ids (Strings).

  require 'rufus-scheduler'

  scheduler =

  job_id = '10d' do
      # ...

  job =
    scheduler.schedule_in '1w' do
      # ...

  job = '1w', :job => true do
      # ...

Those Job instances have a few interesting methods / properties:

id, job_id

Returns the job id.

job = scheduler.schedule_in('10d') do; end
  # => "in_1374072446.8923042_0.0_0"


Returns the scheduler instance itself.


Returns the options passed at the Job creation.

job = scheduler.schedule_in('10d', :tag => 'hello') do; end
  # => { :tag => 'hello' }


Returns the original schedule.

job = scheduler.schedule_in('10d', :tag => 'hello') do; end
  # => '10d'

callable, handler

callable() returns the scheduled block (or the call method of the callable object passed in lieu of a block)

handler() returns nil if a block was scheduled and the instance scheduled else.

# when passing a block

job =
  scheduler.schedule_in('10d') do
    # ...

  # => nil
  # => #<Proc:0x00000001dc6f58@/home/jmettraux/whatever.rb:115>


# when passing something else than a block

class MyHandler
  attr_reader :counter
  def initialize
    @counter = 0
  def call(job, time)
    @counter = @counter + 1

job = scheduler.schedule_in('10d',

  # => #<Method: MyHandler#call>
  # => #<MyHandler:0x0000000163ae88 @counter=0>


Returns the Time instance when the job got created.

job = scheduler.schedule_in('10d', :tag => 'hello') do; end
  # => 2013-07-17 23:48:54 +0900


Returns the last time the job triggered (is usually nil for AtJob and InJob). k

job = scheduler.schedule_every('1d') do; end
# ...
  # => 2013-07-17 23:48:54 +0900

last_work_time, mean_work_time

The job keeps track of how long its work was in the last_work_time attribute. For a one time job (in, at) it's probably not very useful.

The attribute mean_work_time contains a computed mean work time. It's recomputed after every run (if it's a repeat job).


Unschedule the job, preventing it from firing again and removing it from the schedule. This doesn't prevent a running thread for this job to run until its end.


Returns the list of threads currently "hosting" runs of this Job instance.


Interrupts all the work threads currently running for this job instance. They discard their work and are free for their next run (of whatever job).

Note: this doesn't unschedule the Job instance.

Note: if the job is pooled for another run, a free work thread will probably pick up that next run and the job will appear as running again. You'd have to unschedule and kill to make sure the job doesn't run again.


Returns true if there is at least one running Thread hosting a run of this Job instance.


Returns true if the job is scheduled (is due to trigger). For repeat jobs it should return true until the job gets unscheduled. "at" and "in" jobs will respond with false as soon as they start running (execution triggered).

pause, resume, paused?, paused_at

These four methods are only available to CronJob, EveryJob and IntervalJob instances. One can pause or resume such a job thanks to them.

job =
  scheduler.schedule_every('10s') do
    # ...

  # => 2013-07-20 01:22:22 +0900
  # => true
  # => 2013-07-20 01:22:22 +0900

  # => nil


Returns the list of tags attached to this Job instance.

By default, returns an empty array.

job = scheduler.schedule_in('10d') do; end
  # => []

job = scheduler.schedule_in('10d', :tag => 'hello') do; end
  # => [ 'hello' ]

[]=, [], key? and keys

Threads have thread-local variables. Rufus-scheduler jobs have job-local variables.

job =
  @scheduler.schedule_every '1s' do |job|
    job[:timestamp] =
    job[:counter] ||= 0
    job[:counter] += 1

sleep 3.6

  # => 3

  # => true
  # => [ :timestamp, :counter ]

Job-local variables are thread-safe.


Job instances have a #call method. It simply calls the scheduled block or callable immediately.

job =
  @scheduler.schedule_every '10m' do |job|
    # ...

Warning: the Scheduler#on_error handler is not involved. Error handling is the responsibility of the caller.

If the call has to be rescued by the error handler of the scheduler, call(true) might help:

require 'rufus-scheduler'

s =

def s.on_error(job, err)
  p [ 'error in scheduled job', job.class, job.original, err.message ]
  p $!

job =
  s.schedule_in('1d') do
    fail 'again'
  # true lets the error_handler deal with error in the job call

AtJob and InJob methods


Returns when the job will trigger (hopefully).


An alias to time.

EveryJob, IntervalJob and CronJob methods


Returns the next time the job will trigger (hopefully).


Returns how many times the job fired.

EveryJob methods


It returns the scheduling frequency. For a job scheduled "every 20s", it's 20.

It's used to determine if the job frequency is higher than the scheduler frequency (it raises an ArgumentError if that is the case).

IntervalJob methods


Returns the interval scheduled between each execution of the job.

Every jobs use a time duration between each start of their execution, while interval jobs use a time duration between the end of an execution and the start of the next.

CronJob methods


It returns the shortest interval of time between two potential occurences of the job.

For instance:

Rufus::Scheduler.parse('* * * * *').frequency         # ==> 60
Rufus::Scheduler.parse('* * * * * *').frequency       # ==> 1

Rufus::Scheduler.parse('5 23 * * *').frequency        # ==> 24 * 3600
Rufus::Scheduler.parse('5 * * * *').frequency         # ==> 3600
Rufus::Scheduler.parse('10,20,30 * * * *').frequency  # ==> 600

Rufus::Scheduler.parse('10,20,30 * * * * *').frequency  # ==> 10

It's used to determine if the job frequency is higher than the scheduler frequency (it raises an ArgumentError if that is the case).


Cron jobs also have a #brute_frequency method that looks a one year of intervals to determine the shortest delta for the cron. This method can take between 20 to 50 seconds for cron lines that go the second level. #frequency above, when encountering second level cron lines will take a shortcut to answer as quickly as possible with a usable value.

looking up jobs


The scheduler #job(job_id) method can be used to lookup Job instances.

  require 'rufus-scheduler'

  scheduler =

  job_id = '10d' do
      # ...

  # later on...

  job = scheduler.job(job_id)

Scheduler #jobs #at_jobs #in_jobs #every_jobs #interval_jobs and #cron_jobs

Are methods for looking up lists of scheduled Job instances.

Here is an example:

  # let's unschedule all the at jobs


Scheduler#jobs(:tag / :tags => x)

When scheduling a job, one can specify one or more tags attached to the job. These can be used to lookup the job later on. '10d', :tag => 'main_process' do
    # ...
  end '10d', :tags => [ 'main_process', 'side_dish' ] do
    # ...

  # ...

  jobs = => 'main_process')
    # find all the jobs with the 'main_process' tag

  jobs = => [ 'main_process', 'side_dish' ]
    # find all the jobs with the 'main_process' AND 'side_dish' tags


Returns the list of Job instance that have currently running instances.

Whereas other "_jobs" method scan the scheduled job list, this method scans the thread list to find the job. It thus comprises jobs that are running but are not scheduled anymore (that happens for at and in jobs).

misc Scheduler methods


Unschedule a job given directly or by its id.


Shuts down the scheduler, ceases any scheduler/triggering activity.


Shuts down the scheduler, waits (blocks) until all the jobs cease running.


Kills all the job (threads) and then shuts the scheduler down. Radical.


Returns true if the scheduler has been shut down.


Returns the Time instance at which the scheduler got started.

Scheduler #uptime / #uptime_s

Returns since the count of seconds for which the scheduler has been running.

#uptime_s returns this count in a String easier to grasp for humans, like "3d12m45s123".


Let's the current thread join the scheduling thread in rufus-scheduler. The thread comes back when the scheduler gets shut down.


Returns all the threads associated with the scheduler, including the scheduler thread itself.


Lists the work threads associated with the scheduler. The query option defaults to :all.

  • :all : all the work threads
  • :active : all the work threads currently running a Job
  • :vacant : all the work threads currently not running a Job

Note that the main schedule thread will be returned if it is currently running a Job (ie one of those :blocking => true jobs).


Returns true if the arg is a currently scheduled job (see Job#scheduled?).

Scheduler#occurrences(time0, time1)

Returns a hash { job => [ t0, t1, ... ] } mapping jobs to their potential trigger time within the [ time0, time1 ] span.

Please note that, for interval jobs, the #mean_work_time is used, so the result is only a prediction.

Scheduler#timeline(time0, time1)

Like #occurrences but returns a list [ [ t0, job0 ], [ t1, job1 ], ... ] of time + job pairs.

dealing with job errors

The easy, job-granular way of dealing with errors is to rescue and deal with them immediately. The two next sections show examples. Skip them for explanations on how to deal with errors at the scheduler level.

block jobs

As said, jobs could take care of their errors themselves.

scheduler.every '10m' do
    # do something that might fail...
  rescue => e
    $stderr.puts '-' * 80
    $stderr.puts e.message
    $stderr.puts e.stacktrace
    $stderr.puts '-' * 80

callable jobs

Jobs are not only shrunk to blocks, here is how the above would look like with a dedicated class.

scheduler.every '10m', do
  def call(job)
    # do something that might fail...
  rescue => e
    $stderr.puts '-' * 80
    $stderr.puts e.message
    $stderr.puts e.stacktrace
    $stderr.puts '-' * 80

TODO: talk about callable#on_error (if implemented)

(see scheduling handler instances and scheduling handler classes for more about those "callable jobs")


By default, rufus-scheduler intercepts all errors (that inherit from StandardError) and dumps abundent details to $stderr.

If, for example, you'd like to divert that flow to another file (descriptor). You can reassign $stderr for the current Ruby process

$stderr ='/var/log/myapplication.log', 'ab')

or, you can limit that reassignement to the scheduler itself

scheduler.stderr ='/var/log/myapplication.log', 'ab')

Rufus::Scheduler#on_error(job, error)

We've just seen that, by default, rufus-scheduler dumps error information to $stderr. If one needs to completely change what happens in case of error, it's OK to overwrite #on_error

def scheduler.on_error(job, error)

  Logger.warn("intercepted error in #{}: #{error.message}")

Rufus::Scheduler #on_pre_trigger and #on_post_trigger callbacks

One can bind callbacks before and after jobs trigger:

s =

def s.on_pre_trigger(job, trigger_time)
  puts "triggering job #{}..."

def s.on_post_trigger(job, trigger_time)
  puts "triggered job #{}."

s.every '1s' do
  # ...

The trigger_time is the time at which the job triggers. It might be a bit before

Warning: these two callbacks are executed in the scheduler thread, not in the work threads (the threads were the job execution really happens).

Rufus::Scheduler#on_pre_trigger as a guard

Returning false in on_pre_trigger will prevent the job from triggering. Returning anything else (nil, -1, true, ...) will let the job trigger.

Note: your business logic should go in the scheduled block itself (or the scheduled instance). Don't put business logic in on_pre_trigger. Return false for admin reasons (backend down, etc) not for business reasons that are tied to the job itself.

def s.on_pre_trigger(job, trigger_time)

  return false if Backend.down?

  puts "triggering job #{}..."
end options


By default, rufus-scheduler sleeps 0.300 second between every step. At each step it checks for jobs to trigger and so on.

The :frequency option lets you change that 0.300 second to something else.

scheduler = => 5)

It's OK to use a time string to specify the frequency.

scheduler = => '2h10m')
  # this scheduler will sleep 2 hours and 10 minutes between every "step"

Use with care.

:lockfile => "mylockfile.txt"

This feature only works on OSes that support the flock (man 2 flock) call.

Starting the scheduler with :lockfile => ".rufus-scheduler.lock" will make the scheduler attempt to create and lock the file .rufus-scheduler.lock in the current working directory. If that fails, the scheduler will not start.

The idea is to guarantee only one scheduler (in a group of scheduler sharing the same lockfile) is running.

This is useful in environments where the Ruby process holding the scheduler gets started multiple times.

If the lockfile mechanism here is not sufficient, you can plug your custom mechanism. It's explained in advanced lock schemes below.


(since rufus-scheduler 3.0.9)

The scheduler lock is an object that responds to #lock and #unlock. The scheduler calls #lock when starting up. If the answer is false, the scheduler stops its initialization work and won't schedule anything.

Here is a sample of a scheduler lock that only lets the scheduler on host "" start:

class HostLock
  def initialize(lock_name)
    @lock_name = lock_name
  def lock
    @lock_name == `hostname -f`.strip
  def unlock

scheduler = =>''))

By default, the scheduler_lock is an instance of Rufus::Scheduler::NullLock, with a #lock that returns true.


(since rufus-scheduler 3.0.9)

The trigger lock in an object that responds to #lock. The scheduler calls that method on the job lock right before triggering any job. If the answer is false, the trigger doesn't happen, the job is not done (at least not in this scheduler).

Here is a (stupid) PingLock example, it'll only trigger if an "other host" is not responding to ping. Do not use that in production, you don't want to fork a ping process for each trigger attempt...

class PingLock
  def initialize(other_host)
    @other_host = other_host
  def lock
    ! system("ping -c 1 #{@other_host}")

scheduler = =>''))

By default, the trigger_lock is an instance of Rufus::Scheduler::NullLock, with a #lock that always returns true.

As explained in advanced lock schemes, another way to tune that behaviour is by overriding the scheduler's #confirm_lock method. (You could also do that with an #on_pre_trigger callback).


In rufus-scheduler 2.x, by default, each job triggering received its own, brand new, thread of execution. In rufus-scheduler 3.x, execution happens in a pooled work thread. The max work thread count (the pool size) defaults to 28.

One can set this maximum value when starting the scheduler.

scheduler = => 77)

It's OK to increase the :max_work_threads of a running scheduler.

scheduler.max_work_threads += 10


Do not want to store a reference to your rufus-scheduler instance? Then Rufus::Scheduler.singleton can help, it returns a singleon instance of the scheduler, initialized the first time this class method is called.

Rufus::Scheduler.singleton.every '10s' { puts "hello, world!" }

It's OK to pass initialization arguments (like :frequency or :max_work_threads) but they will only be taken into account the first time .singleton is called.

Rufus::Scheduler.singleton(:max_work_threads => 77)
Rufus::Scheduler.singleton(:max_work_threads => 277) # no effect

The .s is a shortcut for .singleton.

Rufus::Scheduler.s.every '10s' { puts "hello, world!" }

advanced lock schemes

As seen above, rufus-scheduler proposes the :lockfile system out of the box. If in a group of schedulers only one is supposed to run, the lockfile mecha prevents schedulers that have not set/created the lockfile from running.

There are situation where this is not sufficient.

By overriding #lock and #unlock, one can customize how his schedulers lock.

This example was provided by Eric Lindvall:

class ZookeptScheduler < Rufus::Scheduler

  def initialize(zookeeper, opts={})
    @zk = zookeeper

  def lock
    @zk_locker = @zk.exclusive_locker('scheduler')
    @zk_locker.lock # returns true if the lock was acquired, false else

  def unlock

  def confirm_lock
    return false if down?
  rescue ZK::Exceptions::LockAssertionFailedError => e
    # we've lost the lock, shutdown (and return false to at least prevent
    # this job from triggering

This uses a zookeeper to make sure only one scheduler in a group of distributed schedulers runs.

The methods #lock and #unlock are overriden and #confirm_lock is provided, to make sure that the lock is still valid.

The #confirm_lock method is called right before a job triggers (if it is provided). The more generic callback #on_pre_trigger is called right after #confirm_lock.

:scheduler_lock and :trigger_lock

(introduced in rufus-scheduler 3.0.9).

Another way of prodiving #lock, #unlock and #confirm_lock to a rufus-scheduler is by using the :scheduler_lock and :trigger_lock options.

See :trigger_lock and :scheduler_lock.

The scheduler lock may be used to prevent a scheduler from starting, while a trigger lock prevents individual jobs from triggering (the scheduler goes on scheduling).

One has to be careful with what goes in #confirm_lock or in a trigger lock, as it gets called before each trigger.

Warning: you may think you're heading towards "high availability" by using a trigger lock and having lots of schedulers at hand. It may be so if you limit yourself to scheduling the same set of jobs at scheduler startup. But if you add schedules at runtime, they stay local to their scheduler. There is no magic that propagates the jobs to all the schedulers in your pack.

parsing cronlines and time strings

Rufus::Scheduler provides a class method .parse to parse time durations and cron strings. It's what it's using when receiving schedules. One can use it diectly (no need to instantiate a Scheduler).

require 'rufus-scheduler'

  # => 777600.0
  # => 777600.0

Rufus::Scheduler.parse('Sun Nov 18 16:01:00 2012').strftime('%c')
  # => 'Sun Nov 18 16:01:00 2012'

Rufus::Scheduler.parse('Sun Nov 18 16:01:00 2012 Europe/Berlin').strftime('%c %z')
  # => 'Sun Nov 18 15:01:00 2012 +0000'

  # => 0.1

Rufus::Scheduler.parse('* * * * *')
  # => #<Rufus::Scheduler::CronLine:0x00000002be5198
  #        @original="* * * * *", @timezone=nil,
  #        @seconds=[0], @minutes=nil, @hours=nil, @days=nil, @months=nil,
  #        @weekdays=nil, @monthdays=nil>

It returns a number when the output is a duration and a CronLine instance when the input is a cron string.

It will raise an ArgumentError if it can't parse the input.

Beyond .parse, there are also .parse_cron and .parse_duration, for finer granularity.

There is an interesting helper method named .to_duration_hash:

require 'rufus-scheduler'

  # => { :m => 1 }
  # => { :m => 1, :s => 2, :ms => 127 }

Rufus::Scheduler.to_duration_hash(62.127, :drop_seconds => true)
  # => { :m => 1 }

cronline notations specific to rufus-scheduler

first Monday, last Sunday et al

To schedule something at noon every first Monday of the month:

scheduler.cron('00 12 * * mon#1') do
  # ...

To schedule something at noon the last Sunday of every month:

scheduler.cron('00 12 * * sun#-1') do
  # ...
# OR
scheduler.cron('00 12 * * sun#L') do
  # ...

Such cronlines can be tested with scripts like:

require 'rufus-scheduler'
  # => 2013-10-26 07:07:08 +0900
Rufus::Scheduler.parse('* * * * mon#1').next_time
  # => 2013-11-04 00:00:00 +0900

L (last day of month)

L can be used in the "day" slot:

In this example, the cronline is supposed to trigger every last day of the month at noon:

require 'rufus-scheduler'
  # => 2013-10-26 07:22:09 +0900
Rufus::Scheduler.parse('00 12 L * *').next_time
  # => 2013-10-31 12:00:00 +0900

a note about timezones

Cron schedules and at schedules support the specification of a timezone.

scheduler.cron '0 22 * * 1-5 America/Chicago' do
  # the job...
end '2013-12-12 14:00 Pacific/Samoa' do
  puts "it's tea time!"

# or even

Rufus::Scheduler.parse("2013-12-12 14:00 Pacific/Saipan")
  # => 2013-12-12 04:00:00 UTC

so Rails?

Yes, I know, all of the above is boring and you're only looking for a snippet to paste in your Ruby-on-Rails application to schedule...

Here is an example initializer:

# config/initializers/scheduler.rb

require 'rufus-scheduler'

# Let's use the rufus-scheduler singleton
s = Rufus::Scheduler.singleton

# Stupid recurrent task...
s.every '1m' do "hello, it's #{}"

And now you tell me that this is good, but you want to schedule stuff from your controller.


class ScheController < ApplicationController

  # GET /sche/
  def index

    job_id = '5s' do "time flies, it's now #{}"

    render :text => "scheduled job #{job_id}"

The rufus-scheduler singleton is instantiated in the config/initializers/scheduler.rb file, it's then available throughout the webapp via Rufus::Scheduler.singleton.

Warning: this works well with single-process Ruby servers like Webrick and Thin. Using rufus-scheduler with Passenger or Unicorn requires a bit more knowledge and tuning, gently provided by a bit of googling and reading, see Faq above.

rails server -d

(Written in reply to )

There is the handy rails server -d that starts a development Rails as a daemon. The annoying thing is that the scheduler as seen above is started in the main process that then gets forked and daemonized. The rufus-scheduler thread (and any other thread) gets lost, no scheduling happens.

I avoid running -d in development mode and bother about daemonizing only for production deployment.

These are two well crafted articles on process daemonization, please read them:

If, anyway, you need something like rails server -d, why not try bundle exec unicorn -D instead? In my (limited) experience, it worked out of the box (well, had to add gem 'unicorn' to Gemfile first).


see getting help above.


MIT, see LICENSE.txt

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