A Lightweight Cron Scheduler for The Async Job Worker Que For Ruby

que-scheduler

Description

que-scheduler is an extension to Que that adds support for scheduling items using a cron style configuration file. It works by running as a que job itself, determining what needs to be run, enqueueing those jobs, then enqueueing itself to check again later.

Installation

To install, add the gem to your Gemfile:

gem 'que-scheduler'

Specify a schedule in a yml file or programmatically (see below). The default location that que-scheduler will look for it is config/que_schedule.yml. The format is essentially the same as resque-scheduler files, but with additional features.

Add a migration to start the job scheduler and prepare the audit table. Note that this migration will fail if Que is set to execute jobs synchronously, i.e. Que::Job.run_synchronously = true.

class CreateQueSchedulerSchema < ActiveRecord::Migration
  def change
    Que::Scheduler::Migrations.migrate!(version: 7)
  end
end

Schedule configuration

The schedule file should be placed here: config/que_schedule.yml. Alternatively if you wish to generate the configuration dynamically, you can set it directly using an initializer (see "Gem configuration" below).

The file is a list of que job classes with arguments and a schedule frequency (in crontab syntax). The format is similar to the resque-scheduler format, though priorities must be supplied as integers, and job classes must be migrated from Resque to Que. Cron syntax can be anything understood by fugit.

It has one additional feature, schedule_type: every_event. This is set on a job that must be run for every single matching cron time that goes by, even if the system is offline over more than one match. To better process these every_event jobs, they are always enqueued with the first argument being the time that they were supposed to be processed.

For example:

CancelAbandonedOrders:
  cron: "*/5 * * * *"

# Specify the job_class, using any name for the key
queue_documents_for_indexing:
  cron: "0 0 * * *"
  class: QueueDocuments
  
# Specify the job queue
ReportOrders:
  cron: "0 0 * * *"
  queue: reporting

# Specify the job priority using Que's number system
BatchOrders:
  cron: "0 0 * * *"
  priority: 25
  
# Specify array job arguments
SendOrders:
  cron: "0 0 * * *"
  args: ['open']

# Specify hash job arguments. Note, this appears as a single hash to `run`, not as kwargs.
SendPreorders:
  cron: "0 0 * * *"
  args:
    order_type: special
  
# Specify a single nil argument
SendPostorders:
  cron: "0 0 * * *"
  args: ~ # See https://stackoverflow.com/a/51990876/1267203
  
# Use simpler cron syntax
SendBilling:
  cron: "@daily"
  
# Use timezone cron syntax
SendCoupons:
  cron: "0 7 * * * America/Los_Angeles"

# Altogether now
all_options_job:
  cron: "0 0 * * *"
  class: QueueDocuments
  queue: reporting
  priority: 25
  args: ['open']
  
# Ensure you never miss a job, even after downtime, by using "schedule_type: every_event"
DailyBatchReport:
  cron: "0 3 * * *"
  # This job will be run every day at 03:00 as normal.
  # However, the "schedule_type: every_event" setting below will ensure that if workers are offline
  # for any amount of time then the backlog will always be enqueued on recovery.
  # See "Schedule types" below for more information.
  schedule_type: every_event

Schedule types

A job can have a schedule_type assigned to it. Valid values are:

1. default - This job will be scheduled in a manner closer to resque-scheduler. If multiple cron times go by during an extended period of downtime (eg a long maintenance window) then only one job will be enqueued when the system starts back up. Multiple missed events are coalesced. This mimics the way resque-scheduler would perform if it were taken down for some time.
2. every_event - Every cron match will result in a job being scheduled. If multiple cron times go by during an extended period of downtime, then a job will be scheduled for every one missed on startup. This schedule_type should be used for regular batch jobs that need to know which time they are running a batch for. The job will always be scheduled with an ISO8601 string of the cron that matched as the first argument.

An example would be an eventing DailyReportJob which summarises a day's sales. If no jobs run for a few days due to a technical failure, then on recovery a report would still be needed for each individual day. "schedule_type: every_event" would ensure this happens.

This feature ensures that jobs which must run for a certain cron match will always eventually execute, even after a total system crash, or even a DB backup restore.

Gem configuration

You can configure some aspects of the gem with a config block (eg in a Rails initializer). The default is given below. You can omit any configuration sections you are not intending to change. It is quite likely you won't have to create this config at all.

Que::Scheduler.configure do |config|
  # The location of the schedule yaml file.
  config.schedule_location = ENV.fetch("QUE_SCHEDULER_CONFIG_LOCATION", "config/que_schedule.yml")

  # The schedule as a hash. You can use this if you want to build the schedule yourself at runtime.
  # This will override the above value if provided.
  config.schedule = {
    SpecifiedByHashTestJob: {
      cron: "02 11 * * *"
    }
  }
  
  # The transaction block adapter. By default, que-scheduler uses the one supplied by que.
  # However if, for example, you rely on listeners to ActiveRecord's exact `transaction` method, or 
  # Sequel's DB.after_commit helper, then you can supply it here.
  config.transaction_adapter = ::Que.method(:transaction)

  # Which queue name the que-scheduler job should self-schedule on. Typically this is the default
  # queue of que, which has a different name in Que 0.x ("") and 1.x ("default").
  # It *must* be the "highest throughput" queue - do not work the scheduler on a "long 
  # running jobs" queue. It is very unlikely you will want to change this. 
  config.que_scheduler_queue = ENV.fetch("QUE_SCHEDULER_QUEUE", "" or "default")
  
  # If que-scheduler is being used with Rails, then it will inherit the time zone from that 
  # framework, and you can leave the value as nil as shown below. However, if you are not using
  # Rails, you may need to set the time zone here. If que-scheduler cannot determine the time zone
  # it will yield an error prompting you for action.
  # If you need to set a value, use the string representation:
  # eg: config.time_zone = "Europe/London"
  config.time_zone = nil
end

Scheduler Audit

An audit table que_scheduler_audit is written to by the scheduler to keep a history of when the scheduler ran to calculate what was necessary to run (if anything). It is created by the included migration tasks.

Additionally, there is the audit table que_scheduler_audit_enqueued. This logs every job that the scheduler enqueues.

que-scheduler comes with the QueSchedulerAuditClearDownJob job built in that you can optionally schedule to clear down audit rows if you don't need to retain them indefinitely. You should add this to your own scheduler config yaml.

For example:

# This will clear down the oldest que-scheduler audit rows. Since que-scheduler
# runs approximately every minute, 129600 is 90 days.
Que::Scheduler::Jobs::QueSchedulerAuditClearDownJob:
  cron: "0 0 * * *"
  args:
    retain_row_count: 129600

Required migrations

When there is a major version (breaking) change, a migration should be run in. The version of the latest migration proceeds at a faster rate than the version of the gem. eg If the gem is on version 3 then the migrations may be on version 6).

To run in all the migrations required up to a number, just migrate to that number with one line, and it will perform all the intermediary steps.

ie, This will perform all migrations necessary up to the latest version, skipping any already performed.

class CreateQueSchedulerSchema < ActiveRecord::Migration
  def change
    Que::Scheduler::Migrations.migrate!(version: 7)
  end
end

The changes in past migrations were:

Version	Changes
1	Enqueued the main Que::Scheduler. This is the job that performs the scheduling.
2	Added the audit table que_scheduler_audit.
3	Added the audit table que_scheduler_audit_enqueued.
4	Updated the the audit tables to use bigints
5	Dropped an unnecessary index
6	Enforced single scheduler job at the trigger level

The changes to the DB (DDL) are all captured in the structure.sql so will be re-run in correctly if squashed - except for the actual scheduling of the job itself (as that is DML). If you squash your migrations make sure this is added as the final line:

Que::Scheduler::Migrations.reenqueue_scheduler_if_missing

HA Redundancy and DB restores

Because of the way que-scheduler works, it requires no additional processes. It is, itself, a Que job. As long as there are Que workers functioning, then jobs will continue to be scheduled correctly. There are no HA concerns to worry about and no namespace collisions between different databases.

Additionally, like Que, when your database is backed up, your scheduling state is stored too. If your workers are down for an extended period, or a DB restore is performed, the scheduler will always be in a coherent state with the rest of your database.

Concurrent scheduler detection

No matter how many tasks you have defined in your schedule, you will only ever need one que-scheduler job enqueued. que-scheduler knows this, and there are DB constraints in place to ensure there is only ever exactly one scheduler job.

It also follows que job design best practices, using ACID guarantees, to ensure that it will never run multiple times. If the scheduler crashes for any reason, it will rollback correctly and try again. It won't schedule jobs twice for a cron match.

How it works

que-scheduler is a job that reads a schedule file, enqueues any jobs it determines that need to be run, then reschedules itself. The flow is as follows:

1. The que-scheduler job runs for the very first time.
2. que-scheduler loads the schedule file. It will not schedule any other jobs, except itself, as it has never run before.
3. Some time later it runs again. It knows what jobs it should be monitoring, and notices that some have are due. It enqueues those jobs and then itself. Repeat.
4. After a deploy that changes the schedule, the job notices any new jobs to schedule, and knows which ones to forget. It does not need to be re-enqueued or restarted.

Testing Configuration

You can add tests to validate your configuration during the spec phase. This will perform a variety of sanity checks and ensure that:

1. The yml is present and valid
2. The job classes exist and are descendants of Que::Job
3. The cron fields are present and valid
4. The queues (if present) are strings
5. The priorities (if present) are integers
6. The schedule_types are known

  describe 'check que_schedule.yml' do
    it 'loads the schedule from the default location' do
      # Will raise an error if any config is invalid
      expect(Que::Scheduler.schedule).not_to be nil
    end
  end

Error Notification

If there is an error during scheduling, que-scheduler will report it using the standard que error notifier. The scheduler will then continue to retry indefinitely.

Upgrading

que-scheduler uses semantic versioning, so major version changes will usually require additional actions to be taken upgrading from one major version to another.

Changelog

A full changelog can be found here: CHANGELOG.md

System requirements

Your postgres database must be at least version 9.5.0.

The latest version of que-scheduler supports Ruby 2.7, though this is largely to allow the gem to work with que 2.x. Recent que-scheduler versions (up to 4.2.2) work with Ruby 2.5.

Ruby 3.x support (and thus que 2.x support) is currently in beta.

Using que 0.x with Rails 6 needs a patch to support it. See the patch and how to use it here: https://github.com/que-rb/que/issues/247#issuecomment-595258236 If that patch is included then que-scheduler will work. This setup is tested, but is not supported.

Inspiration

This gem was inspired by the makers of the excellent Que job scheduler gem.

Contributors

• @bnauta
• @bjeanes
• @JackDanger
• @jish
• @joehorsnell
• @krzyzak
• @papodaca
• @ajoneil
• @ippachi
• @milgner

---

Author: hlascelles
Source code: https://github.com/hlascelles/que-scheduler
License: MIT license

#ruby 

What is GEEK

Buddha Community

Rufus Scheduler: Job Scheduler for Ruby (at, Cron, in and Every Jobs)

rufus-scheduler

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

It uses threads.

Note: maybe are you looking for the README of rufus-scheduler 2.x? (especially if you're using Dashing which is stuck on rufus-scheduler 2.0.24)

Quickstart:

# quickstart.rb

require 'rufus-scheduler'

scheduler = Rufus::Scheduler.new

scheduler.in '3s' do
  puts 'Hello... Rufus'
end

scheduler.join
  #
  # let the current thread join the scheduler thread
  #
  # (please note that this join should be removed when scheduling
  # in a web application (Rails and friends) initializer)

(run with ruby quickstart.rb)

Various forms of scheduling are supported:

require 'rufus-scheduler'

scheduler = Rufus::Scheduler.new

# ...

scheduler.in '10d' do
  # do something in 10 days
end

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

scheduler.every '3h' do
  # do something every 3 hours
end
scheduler.every '3h10m' do
  # do something every 3 hours and 10 minutes
end

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

# ...

Rufus-scheduler uses fugit for parsing time strings, et-orbi for pairing time and tzinfo timezones.

non-features

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

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

A rufus-scheduler instance will go on scheduling while it is present among the objects in a Ruby process. To make it stop scheduling you have to call its #shutdown method.

related and similar gems

• Whenever - let cron call back your Ruby code, trusted and reliable cron drives your schedule
• ruby-clock - a clock process / job scheduler for Ruby
• Clockwork - rufus-scheduler inspired gem
• Crono - an in-Rails cron scheduler
• PerfectSched - highly available distributed cron built on Sequel and more

(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?

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 with 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", "please" and "thanks" are not swear words.

Go read how to report bugs effectively, twice.

Update: help_help.md might help help you.

on Gitter

You can find help via chat over at https://gitter.im/floraison/fugit. It's fugit, et-orbi, and rufus-scheduler combined chat room.

Please be courteous.

issues

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.

faq

• It doesn't work...
• I want a refund
• Passenger and rufus-scheduler
• Passenger and rufus-scheduler (2)
• Passenger in-depth spawn methods
• Passenger in-depth spawn methods (smart spawning)
• The scheduler comes up when running the Rails console or a Rake task
• The job triggers twice
• I don't get any of this, I just want it to work in my Rails application
• [I get "zotime.rb:41:in `initialize': cannot determine timezone from nil"](#i-get-zotimerb41in-initialize-cannot-determine-timezone-from-nil)

scheduling

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 = Rufus::Scheduler.new

scheduler.in '10d' do
  puts "10 days reminder for review X!"
end

scheduler.at '2014/12/24 2000' do
  puts "merry xmas!"
end

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 = Rufus::Scheduler.new

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

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

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

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

# versus

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

# also

job =
  scheduler.in '10d', job: true do
    # ...
  end

#schedule and #repeat

Sometimes it pays to be less verbose.

The #schedule methods schedules an at, in or cron job. It just decides 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 here 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 simply 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'
    stop_oven
    takeout_pie
    job.unschedule
  end
end

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

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

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 responds to #call(), when scheduling:

class Handler
  def self.call(job, time)
    p "- Handler called for #{job.id} at #{time}"
  end
end

scheduler.in '10d', Handler

# or

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

oh = OtherHandler.new('Doe')

scheduler.every '10m', oh
scheduler.in '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
  end
  def call(job)
    @count += 1
    puts ". #{self.class} called at #{Time.now} (#{@count})"
  end
end

job = scheduler.schedule_every '35m', MyHandler

job.handler
  # => #<MyHandler:0x000000021034f0>
job.handler.count
  # => 0

If you want to keep that "block feeling":

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

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

name: string

Sets the name of the job.

scheduler.cron '*/15 8 * * *', name: 'Robert' do |job|
  puts "A, it's #{Time.now} and my name is #{job.name}"
end

job1 =
  scheduler.schedule_cron '*/30 9 * * *', n: 'temporary' do |job|
    puts "B, it's #{Time.now} and my name is #{job.name}"
  end
# ...
job1.name = 'Beowulf'

blocking: true

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

overlap: false

Since, by default, jobs are triggered in their own new threads, 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 instances is already running.

The :overlap option is considered before the :mutex option when the scheduler is reviewing jobs for triggering.

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 from entering (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

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

The :overlap option is considered before the :mutex option when the scheduler is reviewing jobs for triggering.

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.

scheduler.in '10d', timeout: '1d' do
  begin
    # ... do something
  rescue Rufus::Scheduler::TimeoutError
    # ... that something got interrupted after 1 day
  end
end

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 as well, the :first will point to the first time the job has to trigger, the following trigger times are then determined by the cron string.

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

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

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

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

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

job.first_at = Time.now + 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 occurrence for immediate triggering. Consider:

require 'rufus-scheduler'

s = Rufus::Scheduler.new

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

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

s.join

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
end

scheduler.every '10m', last_at: Time.now + 10 * 3600 do
  # ... do something every 10 minutes for 10 hours
end

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

:last, :last_at and :last_in all accept a point in time or a duration (number or time string). Use the symbol you think makes 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
end

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

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
  # ...
end

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

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

# 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 returns Job instances instead of Job ids (Strings).

  require 'rufus-scheduler'

  scheduler = Rufus::Scheduler.new

  job_id =
    scheduler.in '10d' do
      # ...
    end

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

  job =
    scheduler.in '1w', job: true do
      # ...
    end

Those Job instances have a few interesting methods / properties:

id, job_id

Returns the job id.

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

scheduler

Returns the scheduler instance itself.

opts

Returns the options passed at the Job creation.

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

original

Returns the original schedule.

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

# when passing a block

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

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

and

# when passing something else than a block

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

job = scheduler.schedule_in('10d', MyHandler.new)

job.handler
  # => #<Method: MyHandler#call>
job.callable
  # => #<MyHandler:0x0000000163ae88 @counter=0>

source_location

Added to rufus-scheduler 3.8.0.

Returns the array [ 'path/to/file.rb', 123 ] like Proc#source_location does.

require 'rufus-scheduler'

scheduler = Rufus::Scheduler.new

job = scheduler.schedule_every('2h') { p Time.now }

p job.source_location
  # ==> [ '/home/jmettraux/rufus-scheduler/test.rb', 6 ]

scheduled_at

Returns the Time instance when the job got created.

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

last_time

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

job = scheduler.schedule_every('10s') do; end

job.scheduled_at
  # => 2013-07-17 23:48:54 +0900
job.last_time
  # => nil (since we've just scheduled it)

# after 10 seconds

job.scheduled_at
  # => 2013-07-17 23:48:54 +0900 (same as above)
job.last_time
  # => 2013-07-17 23:49:04 +0900

previous_time

Returns the previous #next_time

scheduler.every('10s') do |job|
  puts "job scheduled for #{job.previous_time} triggered at #{Time.now}"
  puts "next time will be around #{job.next_time}"
  puts "."
end

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).

next_times(n)

Returns an array of EtOrbi::EoTime instances (Time instances with a designated time zone), listing the n next occurrences for this job.

Please note that for "interval" jobs, a mean work time is computed each time and it's used by this #next_times(n) method to approximate the next times beyond the immediate next time.

unschedule

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.

threads

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

kill

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.

running?

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

scheduled?

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 jobs thanks to these methods.

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

job.pause
  # => 2013-07-20 01:22:22 +0900
job.paused?
  # => true
job.paused_at
  # => 2013-07-20 01:22:22 +0900

job.resume
  # => nil

tags

Returns the list of tags attached to this Job instance.

By default, returns an empty array.

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

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

[]=, [], key?, has_key?, keys, values, and entries

Threads have thread-local variables, similarly Rufus-scheduler jobs have job-local variables. Those are more like a dict with thread-safe access.

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

sleep 3.6

job[:counter]
  # => 3

job.key?(:timestamp) # => true
job.has_key?(:timestamp) # => true
job.keys # => [ :timestamp, :counter ]

Locals can be set at schedule time:

job0 =
  @scheduler.schedule_cron '*/15 12 * * *', locals: { a: 0 } do
    # ...
  end
job1 =
  @scheduler.schedule_cron '*/15 13 * * *', l: { a: 1 } do
    # ...
  end

One can fetch the Hash directly with Job#locals. Of course, direct manipulation is not thread-safe.

job.locals.entries do |k, v|
  p "#{k}: #{v}"
end

call

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

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

job.call

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 = Rufus::Scheduler.new

def s.on_error(job, err)
  if job
    p [ 'error in scheduled job', job.class, job.original, err.message ]
  else
    p [ 'error while scheduling', err.message ]
  end
rescue
  p $!
end

job =
  s.schedule_in('1d') do
    fail 'again'
  end

job.call(true)
  #
  # true lets the error_handler deal with error in the job call

AtJob and InJob methods

time

Returns when the job will trigger (hopefully).

next_time

An alias for time.

EveryJob, IntervalJob and CronJob methods

next_time

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

count

Returns how many times the job fired.

EveryJob methods

frequency

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

interval

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

brute_frequency

An expensive method to run, it's brute. It caches its results. By default it runs for 2017 (a non leap-year).

  require 'rufus-scheduler'

  Rufus::Scheduler.parse('* * * * *').brute_frequency
    #
    # => #<Fugit::Cron::Frequency:0x00007fdf4520c5e8
    #      @span=31536000.0, @delta_min=60, @delta_max=60,
    #      @occurrences=525600, @span_years=1.0, @yearly_occurrences=525600.0>
      #
      # Occurs 525600 times in a span of 1 year (2017) and 1 day.
      # There are least 60 seconds between "triggers" and at most 60 seconds.

  Rufus::Scheduler.parse('0 12 * * *').brute_frequency
    # => #<Fugit::Cron::Frequency:0x00007fdf451ec6d0
    #      @span=31536000.0, @delta_min=86400, @delta_max=86400,
    #      @occurrences=365, @span_years=1.0, @yearly_occurrences=365.0>
  Rufus::Scheduler.parse('0 12 * * *').brute_frequency.to_debug_s
    # => "dmin: 1D, dmax: 1D, ocs: 365, spn: 52W1D, spnys: 1, yocs: 365"
      #
      # 365 occurrences, at most 1 day between each, at least 1 day.

The CronJob#frequency method found in rufus-scheduler < 3.5 has been retired.

looking up jobs

Scheduler#job(job_id)

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

  require 'rufus-scheduler'

  scheduler = Rufus::Scheduler.new

  job_id =
    scheduler.in '10d' do
      # ...
    end

  # 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.at_jobs.each(&:unschedule)

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 look up the job later on.

  scheduler.in '10d', tag: 'main_process' do
    # ...
  end
  scheduler.in '10d', tags: [ 'main_process', 'side_dish' ] do
    # ...
  end

  # ...

  jobs = scheduler.jobs(tag: 'main_process')
    # find all the jobs with the 'main_process' tag

  jobs = scheduler.jobs(tags: [ 'main_process', 'side_dish' ]
    # find all the jobs with the 'main_process' AND 'side_dish' tags

Scheduler#running_jobs

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

Scheduler#unschedule(job_or_job_id)

Unschedule a job given directly or by its id.

Scheduler#shutdown

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

Scheduler#shutdown(:wait)

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

Scheduler#shutdown(wait: n)

Shuts down the scheduler, waits (blocks) at most n seconds until all the jobs cease running. (Jobs are killed after n seconds have elapsed).

Scheduler#shutdown(:kill)

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

Scheduler#down?

Returns true if the scheduler has been shut down.

Scheduler#started_at

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".

Scheduler#join

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

#join is mostly used in standalone scheduling script (or tiny one file examples). Calling #join from a web application initializer will probably hijack the main thread and prevent the web application from being served. Do not put a #join in such a web application initializer file.

Scheduler#threads

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

Scheduler#work_threads(query=:all/:active/:vacant)

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).

Scheduler#scheduled?(job_or_job_id)

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
  begin
    # do something that might fail...
  rescue => e
    $stderr.puts '-' * 80
    $stderr.puts e.message
    $stderr.puts e.stacktrace
    $stderr.puts '-' * 80
  end
end

callable jobs

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

scheduler.every '10m', Class.new 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
  end
end

TODO: talk about callable#on_error (if implemented)

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

Rufus::Scheduler#stderr=

By default, rufus-scheduler intercepts all errors (that inherit from StandardError) and dumps abundant 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 = File.open('/var/log/myapplication.log', 'ab')

or, you can limit that reassignement to the scheduler itself

scheduler.stderr = File.open('/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 #{job.id}: #{error.message}")
end

On Rails, the on_error method redefinition might look like:

def scheduler.on_error(job, error)

  Rails.logger.error(
    "err#{error.object_id} rufus-scheduler intercepted #{error.inspect}" +
    " in job #{job.inspect}")
  error.backtrace.each_with_index do |line, i|
    Rails.logger.error(
      "err#{error.object_id} #{i}: #{line}")
  end
end

Callbacks

Rufus::Scheduler #on_pre_trigger and #on_post_trigger callbacks

One can bind callbacks before and after jobs trigger:

s = Rufus::Scheduler.new

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

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

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

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

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

Rufus::Scheduler#around_trigger

One can create an around callback which will wrap a job:

def s.around_trigger(job)
  t = Time.now
  puts "Starting job #{job.id}..."
  yield
  puts "job #{job.id} finished in #{Time.now-t} seconds."
end

The around callback is executed in the thread.

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 #{job.id}..."
end

Rufus::Scheduler.new options

:frequency

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 = Rufus::Scheduler.new(frequency: 5)

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

scheduler = Rufus::Scheduler.new(frequency: '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 schedulers 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.

:scheduler_lock

(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 "coffee.example.com" start:

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

scheduler =
  Rufus::Scheduler.new(scheduler_lock: HostLock.new('coffee.example.com'))

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

:trigger_lock

(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
  end
  def lock
    ! system("ping -c 1 #{@other_host}")
  end
end

scheduler =
  Rufus::Scheduler.new(trigger_lock: PingLock.new('main.example.com'))

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).

:max_work_threads

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 = Rufus::Scheduler.new(max_work_threads: 77)

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

scheduler.max_work_threads += 10

Rufus::Scheduler.singleton

Do not want to store a reference to your rufus-scheduler instance? Then Rufus::Scheduler.singleton can help, it returns a singleton 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 mechanism prevents schedulers that have not set/created the lockfile from running.

There are situations where this is not sufficient.

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

This example was provided by Eric Lindvall:

class ZookeptScheduler < Rufus::Scheduler

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

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

  def unlock
    @zk_locker.unlock
  end

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

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

The methods #lock and #unlock are overridden 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

(Please note that fugit does the heavy-lifting parsing work for rufus-scheduler).

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 directly (no need to instantiate a Scheduler).

require 'rufus-scheduler'

Rufus::Scheduler.parse('1w2d')
  # => 777600.0
Rufus::Scheduler.parse('1.0w1.0d')
  # => 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'

Rufus::Scheduler.parse(0.1)
  # => 0.1

Rufus::Scheduler.parse('* * * * *')
  # => #<Fugit::Cron:0x00007fb7a3045508
  #      @original="* * * * *", @cron_s=nil,
  #      @seconds=[0], @minutes=nil, @hours=nil, @monthdays=nil, @months=nil,
  #      @weekdays=nil, @zone=nil, @timezone=nil>

It returns a number when the input is a duration and a Fugit::Cron 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'

Rufus::Scheduler.to_duration_hash(60)
  # => { :m => 1 }
Rufus::Scheduler.to_duration_hash(62.127)
  # => { :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
  # ...
end

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

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

Such cronlines can be tested with scripts like:

require 'rufus-scheduler'

Time.now
  # => 2013-10-26 07:07:08 +0900
Rufus::Scheduler.parse('* * * * mon#1').next_time.to_s
  # => 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'
Time.now
  # => 2013-10-26 07:22:09 +0900
Rufus::Scheduler.parse('00 12 L * *').next_time.to_s
  # => 2013-10-31 12:00:00 +0900

negative day (x days before the end of the month)

It's OK to pass negative values in the "day" slot:

scheduler.cron '0 0 -5 * *' do
  # do it at 00h00 5 days before the end of the month...
end

Negative ranges (-10--5-: 10 days before the end of the month to 5 days before the end of the month) are OK, but mixed positive / negative ranges will raise an ArgumentError.

Negative ranges with increments (-10---2/2) are accepted as well.

Descending day ranges are not accepted (10-8 or -8--10 for example).

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

scheduler.at '2013-12-12 14:00 Pacific/Samoa' do
  puts "it's tea time!"
end

# or even

Rufus::Scheduler.parse("2013-12-12 14:00 Pacific/Saipan")
  # => #<Rufus::Scheduler::ZoTime:0x007fb424abf4e8 @seconds=1386820800.0, @zone=#<TZInfo::DataTimezone: Pacific/Saipan>, @time=nil>

I get "zotime.rb:41:in `initialize': cannot determine timezone from nil"

For when you see an error like:

rufus-scheduler/lib/rufus/scheduler/zotime.rb:41:
  in `initialize':
    cannot determine timezone from nil (etz:nil,tnz:"中国标准时间",tzid:nil)
      (ArgumentError)
    from rufus-scheduler/lib/rufus/scheduler/zotime.rb:198:in `new'
    from rufus-scheduler/lib/rufus/scheduler/zotime.rb:198:in `now'
    from rufus-scheduler/lib/rufus/scheduler.rb:561:in `start'
    ...

It may happen on Windows or on systems that poorly hint to Ruby which timezone to use. It should be solved by setting explicitly the ENV['TZ'] before the scheduler instantiation:

ENV['TZ'] = 'Asia/Shanghai'
scheduler = Rufus::Scheduler.new
scheduler.every '2s' do
  puts "#{Time.now} Hello #{ENV['TZ']}!"
end

On Rails you might want to try with:

ENV['TZ'] = Time.zone.name # Rails only
scheduler = Rufus::Scheduler.new
scheduler.every '2s' do
  puts "#{Time.now} Hello #{ENV['TZ']}!"
end

(Hat tip to Alexander in gh-230)

Rails sets its timezone under config/application.rb.

Rufus-Scheduler 3.3.3 detects the presence of Rails and uses its timezone setting (tested with Rails 4), so setting ENV['TZ'] should not be necessary.

The value can be determined thanks to https://en.wikipedia.org/wiki/List_of_tz_database_time_zones.

Use a "continent/city" identifier (for example "Asia/Shanghai"). Do not use an abbreviation (not "CST") and do not use a local time zone name (not "中国标准时间" nor "Eastern Standard Time" which, for instance, points to a time zone in America and to another one in Australia...).

If the error persists (and especially on Windows), try to add the tzinfo-data to your Gemfile, as in:

gem 'tzinfo-data'

or by manually requiring it before requiring rufus-scheduler (if you don't use Bundler):

require 'tzinfo/data'
require 'rufus-scheduler'

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

  Rails.logger.info "hello, it's #{Time.now}"
  Rails.logger.flush
end

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

Maybe:

class ScheController < ApplicationController

  # GET /sche/
  #
  def index

    job_id =
      Rufus::Scheduler.singleton.in '5s' do
        Rails.logger.info "time flies, it's now #{Time.now}"
      end

    render text: "scheduled job #{job_id}"
  end
end

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.

avoid scheduling when running the Ruby on Rails console

(Written in reply to gh-186)

If you don't want rufus-scheduler to trigger anything while running the Ruby on Rails console, running for tests/specs, or running from a Rake task, you can insert a conditional return statement before jobs are added to the scheduler instance:

#
# config/initializers/scheduler.rb

require 'rufus-scheduler'

return if defined?(Rails::Console) || Rails.env.test? || File.split($PROGRAM_NAME).last == 'rake'
  #
  # do not schedule when Rails is run from its console, for a test/spec, or
  # from a Rake task

# return if $PROGRAM_NAME.include?('spring')
  #
  # see https://github.com/jmettraux/rufus-scheduler/issues/186

s = Rufus::Scheduler.singleton

s.every '1m' do
  Rails.logger.info "hello, it's #{Time.now}"
  Rails.logger.flush
end

(Beware later version of Rails where Spring takes care pre-running the initializers. Running spring stop or disabling Spring might be necessary in some cases to see changes to initializers being taken into account.)

rails server -d

(Written in reply to https://github.com/jmettraux/rufus-scheduler/issues/165 )

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:

• https://www.mikeperham.com/2014/09/22/dont-daemonize-your-daemons/
• https://www.mikeperham.com/2014/07/07/use-runit/

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).

executor / reloader

You might benefit from wraping your scheduled code in the executor or reloader. Read more here: https://guides.rubyonrails.org/threading_and_code_execution.html

support

see getting help above.

---

Author: jmettraux
Source code: https://github.com/jmettraux/rufus-scheduler
License: MIT license

#ruby 

Cron Job Scheduling In Laravel

Today I will show you Cron Job Scheduling In Laravel, many time we require to run some piece of code specific interval time period in laravel and we need to run manually every time but command scheduler through we can run and create cron job in laravel.

So, here i will teach you how to create cron job in laravel, and how to create custom command in laravel.

Cron Job Scheduling In Laravel

https://websolutionstuff.com/post/cron-job-scheduling-in-laravel

#cron job scheduling in laravel #laravel #scheduling #scheduler #cron #how to create cron job in laravel

A Lightweight Cron Scheduler for The Async Job Worker Que For Ruby

que-scheduler

Description

que-scheduler is an extension to Que that adds support for scheduling items using a cron style configuration file. It works by running as a que job itself, determining what needs to be run, enqueueing those jobs, then enqueueing itself to check again later.

Installation

To install, add the gem to your Gemfile:

gem 'que-scheduler'

Specify a schedule in a yml file or programmatically (see below). The default location that que-scheduler will look for it is config/que_schedule.yml. The format is essentially the same as resque-scheduler files, but with additional features.

Add a migration to start the job scheduler and prepare the audit table. Note that this migration will fail if Que is set to execute jobs synchronously, i.e. Que::Job.run_synchronously = true.

class CreateQueSchedulerSchema < ActiveRecord::Migration
  def change
    Que::Scheduler::Migrations.migrate!(version: 7)
  end
end

Schedule configuration

The schedule file should be placed here: config/que_schedule.yml. Alternatively if you wish to generate the configuration dynamically, you can set it directly using an initializer (see "Gem configuration" below).

The file is a list of que job classes with arguments and a schedule frequency (in crontab syntax). The format is similar to the resque-scheduler format, though priorities must be supplied as integers, and job classes must be migrated from Resque to Que. Cron syntax can be anything understood by fugit.

It has one additional feature, schedule_type: every_event. This is set on a job that must be run for every single matching cron time that goes by, even if the system is offline over more than one match. To better process these every_event jobs, they are always enqueued with the first argument being the time that they were supposed to be processed.

For example:

CancelAbandonedOrders:
  cron: "*/5 * * * *"

# Specify the job_class, using any name for the key
queue_documents_for_indexing:
  cron: "0 0 * * *"
  class: QueueDocuments
  
# Specify the job queue
ReportOrders:
  cron: "0 0 * * *"
  queue: reporting

# Specify the job priority using Que's number system
BatchOrders:
  cron: "0 0 * * *"
  priority: 25
  
# Specify array job arguments
SendOrders:
  cron: "0 0 * * *"
  args: ['open']

# Specify hash job arguments. Note, this appears as a single hash to `run`, not as kwargs.
SendPreorders:
  cron: "0 0 * * *"
  args:
    order_type: special
  
# Specify a single nil argument
SendPostorders:
  cron: "0 0 * * *"
  args: ~ # See https://stackoverflow.com/a/51990876/1267203
  
# Use simpler cron syntax
SendBilling:
  cron: "@daily"
  
# Use timezone cron syntax
SendCoupons:
  cron: "0 7 * * * America/Los_Angeles"

# Altogether now
all_options_job:
  cron: "0 0 * * *"
  class: QueueDocuments
  queue: reporting
  priority: 25
  args: ['open']
  
# Ensure you never miss a job, even after downtime, by using "schedule_type: every_event"
DailyBatchReport:
  cron: "0 3 * * *"
  # This job will be run every day at 03:00 as normal.
  # However, the "schedule_type: every_event" setting below will ensure that if workers are offline
  # for any amount of time then the backlog will always be enqueued on recovery.
  # See "Schedule types" below for more information.
  schedule_type: every_event

Schedule types

A job can have a schedule_type assigned to it. Valid values are:

1. default - This job will be scheduled in a manner closer to resque-scheduler. If multiple cron times go by during an extended period of downtime (eg a long maintenance window) then only one job will be enqueued when the system starts back up. Multiple missed events are coalesced. This mimics the way resque-scheduler would perform if it were taken down for some time.
2. every_event - Every cron match will result in a job being scheduled. If multiple cron times go by during an extended period of downtime, then a job will be scheduled for every one missed on startup. This schedule_type should be used for regular batch jobs that need to know which time they are running a batch for. The job will always be scheduled with an ISO8601 string of the cron that matched as the first argument.

An example would be an eventing DailyReportJob which summarises a day's sales. If no jobs run for a few days due to a technical failure, then on recovery a report would still be needed for each individual day. "schedule_type: every_event" would ensure this happens.

This feature ensures that jobs which must run for a certain cron match will always eventually execute, even after a total system crash, or even a DB backup restore.

Gem configuration

You can configure some aspects of the gem with a config block (eg in a Rails initializer). The default is given below. You can omit any configuration sections you are not intending to change. It is quite likely you won't have to create this config at all.

Que::Scheduler.configure do |config|
  # The location of the schedule yaml file.
  config.schedule_location = ENV.fetch("QUE_SCHEDULER_CONFIG_LOCATION", "config/que_schedule.yml")

  # The schedule as a hash. You can use this if you want to build the schedule yourself at runtime.
  # This will override the above value if provided.
  config.schedule = {
    SpecifiedByHashTestJob: {
      cron: "02 11 * * *"
    }
  }
  
  # The transaction block adapter. By default, que-scheduler uses the one supplied by que.
  # However if, for example, you rely on listeners to ActiveRecord's exact `transaction` method, or 
  # Sequel's DB.after_commit helper, then you can supply it here.
  config.transaction_adapter = ::Que.method(:transaction)

  # Which queue name the que-scheduler job should self-schedule on. Typically this is the default
  # queue of que, which has a different name in Que 0.x ("") and 1.x ("default").
  # It *must* be the "highest throughput" queue - do not work the scheduler on a "long 
  # running jobs" queue. It is very unlikely you will want to change this. 
  config.que_scheduler_queue = ENV.fetch("QUE_SCHEDULER_QUEUE", "" or "default")
  
  # If que-scheduler is being used with Rails, then it will inherit the time zone from that 
  # framework, and you can leave the value as nil as shown below. However, if you are not using
  # Rails, you may need to set the time zone here. If que-scheduler cannot determine the time zone
  # it will yield an error prompting you for action.
  # If you need to set a value, use the string representation:
  # eg: config.time_zone = "Europe/London"
  config.time_zone = nil
end

Scheduler Audit

An audit table que_scheduler_audit is written to by the scheduler to keep a history of when the scheduler ran to calculate what was necessary to run (if anything). It is created by the included migration tasks.

Additionally, there is the audit table que_scheduler_audit_enqueued. This logs every job that the scheduler enqueues.

que-scheduler comes with the QueSchedulerAuditClearDownJob job built in that you can optionally schedule to clear down audit rows if you don't need to retain them indefinitely. You should add this to your own scheduler config yaml.

For example:

# This will clear down the oldest que-scheduler audit rows. Since que-scheduler
# runs approximately every minute, 129600 is 90 days.
Que::Scheduler::Jobs::QueSchedulerAuditClearDownJob:
  cron: "0 0 * * *"
  args:
    retain_row_count: 129600

Required migrations

When there is a major version (breaking) change, a migration should be run in. The version of the latest migration proceeds at a faster rate than the version of the gem. eg If the gem is on version 3 then the migrations may be on version 6).

To run in all the migrations required up to a number, just migrate to that number with one line, and it will perform all the intermediary steps.

ie, This will perform all migrations necessary up to the latest version, skipping any already performed.

class CreateQueSchedulerSchema < ActiveRecord::Migration
  def change
    Que::Scheduler::Migrations.migrate!(version: 7)
  end
end

The changes in past migrations were:

Version	Changes
1	Enqueued the main Que::Scheduler. This is the job that performs the scheduling.
2	Added the audit table que_scheduler_audit.
3	Added the audit table que_scheduler_audit_enqueued.
4	Updated the the audit tables to use bigints
5	Dropped an unnecessary index
6	Enforced single scheduler job at the trigger level

The changes to the DB (DDL) are all captured in the structure.sql so will be re-run in correctly if squashed - except for the actual scheduling of the job itself (as that is DML). If you squash your migrations make sure this is added as the final line:

Que::Scheduler::Migrations.reenqueue_scheduler_if_missing

HA Redundancy and DB restores

Because of the way que-scheduler works, it requires no additional processes. It is, itself, a Que job. As long as there are Que workers functioning, then jobs will continue to be scheduled correctly. There are no HA concerns to worry about and no namespace collisions between different databases.

Additionally, like Que, when your database is backed up, your scheduling state is stored too. If your workers are down for an extended period, or a DB restore is performed, the scheduler will always be in a coherent state with the rest of your database.

Concurrent scheduler detection

No matter how many tasks you have defined in your schedule, you will only ever need one que-scheduler job enqueued. que-scheduler knows this, and there are DB constraints in place to ensure there is only ever exactly one scheduler job.

It also follows que job design best practices, using ACID guarantees, to ensure that it will never run multiple times. If the scheduler crashes for any reason, it will rollback correctly and try again. It won't schedule jobs twice for a cron match.

How it works

que-scheduler is a job that reads a schedule file, enqueues any jobs it determines that need to be run, then reschedules itself. The flow is as follows:

1. The que-scheduler job runs for the very first time.
2. que-scheduler loads the schedule file. It will not schedule any other jobs, except itself, as it has never run before.
3. Some time later it runs again. It knows what jobs it should be monitoring, and notices that some have are due. It enqueues those jobs and then itself. Repeat.
4. After a deploy that changes the schedule, the job notices any new jobs to schedule, and knows which ones to forget. It does not need to be re-enqueued or restarted.

Testing Configuration

You can add tests to validate your configuration during the spec phase. This will perform a variety of sanity checks and ensure that:

1. The yml is present and valid
2. The job classes exist and are descendants of Que::Job
3. The cron fields are present and valid
4. The queues (if present) are strings
5. The priorities (if present) are integers
6. The schedule_types are known

  describe 'check que_schedule.yml' do
    it 'loads the schedule from the default location' do
      # Will raise an error if any config is invalid
      expect(Que::Scheduler.schedule).not_to be nil
    end
  end

Error Notification

If there is an error during scheduling, que-scheduler will report it using the standard que error notifier. The scheduler will then continue to retry indefinitely.

Upgrading

que-scheduler uses semantic versioning, so major version changes will usually require additional actions to be taken upgrading from one major version to another.

Changelog

A full changelog can be found here: CHANGELOG.md

System requirements

Your postgres database must be at least version 9.5.0.

The latest version of que-scheduler supports Ruby 2.7, though this is largely to allow the gem to work with que 2.x. Recent que-scheduler versions (up to 4.2.2) work with Ruby 2.5.

Ruby 3.x support (and thus que 2.x support) is currently in beta.

Using que 0.x with Rails 6 needs a patch to support it. See the patch and how to use it here: https://github.com/que-rb/que/issues/247#issuecomment-595258236 If that patch is included then que-scheduler will work. This setup is tested, but is not supported.

Inspiration

This gem was inspired by the makers of the excellent Que job scheduler gem.

Contributors

• @bnauta
• @bjeanes
• @JackDanger
• @jish
• @joehorsnell
• @krzyzak
• @papodaca
• @ajoneil
• @ippachi
• @milgner

---

Author: hlascelles
Source code: https://github.com/hlascelles/que-scheduler
License: MIT license

#ruby 

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7 Reasons to Trust Ruby on Rails

Ruby on Rails is an amazing web development framework. Known for its adaptability, it powers 3,903,258 sites internationally. Ruby on Rails development speeds up the interaction within web applications. It is productive to such an extent that a Ruby on Rails developer can develop an application 25% to 40% quicker when contrasted with different frameworks. 

Around 2.1% (21,034) of the best 1 million sites utilize Ruby on Rails. The framework is perfect for creating web applications in every industry. Regardless of whether it's medical services or vehicles, Rails carries a higher degree of dynamism to each application. 

Be that as it may, what makes the framework so mainstream? Some say that it is affordable, some say it is on the grounds that the Ruby on Rails improvement environment is simple and basic. There are numerous reasons that make it ideal for creating dynamic applications.

Read more: Best Ruby on Rails projects Examples

7 reasons Ruby on Rails is preferred

There are a few other well-known backend services for web applications like Django, Flask, Laravel, and that's only the tip of the iceberg. So for what reason should organizations pick Ruby on Rails application development? We believe the accompanying reasons will feature why different organizations trust the framework -

Quick prototyping 

Rails works on building MVPs in a couple of months. Organizations incline toward Ruby on Rails quick application development as it offers them more opportunity to showcase the elements. Regular development groups accomplish 25% to 40% higher efficiency when working with Rails. Joined with agile, Ruby on Rails empowers timely delivery.

Basic and simple 

Ruby on Rails is easy to arrange and work with. It is not difficult to learn also. Both of these things are conceivable as a result of Ruby. The programming language has one of the most straightforward sentence structures, which is like the English language. Ruby is a universally useful programming language, working on things for web applications. 

Cost-effective 

Probably the greatest advantage of Rails is that it is very reasonable. The system is open-source, which implies there is no licensing charge included. Aside from that, engineers are additionally effectively accessible, that too at a lower cost. There are a large number of Ruby on Rails engineers for hire at an average compensation of $107,381 each year. 

Startup-friendly

Ruby on Rails is regularly known as "the startup technology." It offers adaptable, fast, and dynamic web improvement to new companies. Most arising organizations and new businesses lean toward this as a direct result of its quick application improvement capacities. It prompts quicker MVP development, which permits new companies to rapidly search for venture investment. 

Adaptable framework 

Ruby on Rails is profoundly adaptable and versatile. In any event, when engineers miss adding any functions, they can utilize different modules to add highlights into the application. Aside from that, they can likewise reclassify components by eliminating or adding them during the development environment. Indeed, even individual projects can be extended and changed. 

Convention over configuration

Regardless of whether it's Ruby on Rails enterprise application development or ecommerce-centered applications, the system utilizes convention over configuration. Developers don't have to go through hours attempting to set up the Ruby on Rails improvement environment. The standard conventions cover everything, improving on things for engineers on the task. The framework likewise utilizes the standard of "Don't Repeat Yourself" to guarantee there are no redundancies. 

Versatile applications 

At the point when organizations scale, applications regularly slack. However, this isn't the situation with Ruby on Rails web application development. The system powers sites with high traffic, It can deal with a huge load of worker demands immediately. Adaptability empowers new businesses to keep utilizing the structure even after they prepare their first model for dispatch. 

Checkout Pros and Cons of Ruby on Rails for Web Development

Bottom Line 

Ruby on Rails is as yet a significant framework utilized by organizations all over the world - of every kind. In this day and age, it is probably the best framework to digitize endeavors through powerful web applications.

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