resque-scheduler
================


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### Description

Resque-scheduler is an extension to [Resque](http://github.com/resque/resque)
that adds support for queueing items in the future.

Job scheduling is supported in two different way: Recurring (scheduled) and
Delayed.

Scheduled jobs are like cron jobs, recurring on a regular basis.  Delayed
jobs are resque jobs that you want to run at some point in the future.
The syntax is pretty explanatory:

```ruby
Resque.enqueue_in(5.days, SendFollowupEmail, argument) # runs a job in 5 days, calling SendFollowupEmail.perform(argument)
# or
Resque.enqueue_at(5.days.from_now, SomeJob, argument) # runs a job at a specific time, calling SomeJob.perform(argument)
```

### Documentation

This `README` covers what most people need to know.  If you're looking
for details on individual methods, you might want to try the
[rdoc](http://rdoc.info/github/resque/resque-scheduler/master/frames).

### Installation

To install:

    gem install resque-scheduler

If you use a Gemfile:

```ruby
gem 'resque-scheduler'
```

Adding the resque:scheduler rake task:

```ruby
require 'resque/scheduler/tasks'
```

### Rake integration

By default, `resque-scheduler` depends on the "resque:setup" rake task.
Since you probably already have this task, lets just put our
configuration there.  `resque-scheduler` pretty much needs to know
everything `resque` needs to know.

```ruby
# Resque tasks
require 'resque/tasks'
require 'resque/scheduler/tasks'

namespace :resque do
  task :setup do
    require 'resque'

    # you probably already have this somewhere
    Resque.redis = 'localhost:6379'
  end

  task :setup_schedule => :setup do
    require 'resque-scheduler'

    # If you want to be able to dynamically change the schedule,
    # uncomment this line.  A dynamic schedule can be updated via the
    # Resque::Scheduler.set_schedule (and remove_schedule) methods.
    # When dynamic is set to true, the scheduler process looks for
    # schedule changes and applies them on the fly.
    # Note: This feature is only available in >=2.0.0.
    # Resque::Scheduler.dynamic = true

    # The schedule doesn't need to be stored in a YAML, it just needs to
    # be a hash.  YAML is usually the easiest.
    Resque.schedule = YAML.load_file('your_resque_schedule.yml')

    # If your schedule already has +queue+ set for each job, you don't
    # need to require your jobs.  This can be an advantage since it's
    # less code that resque-scheduler needs to know about. But in a small
    # project, it's usually easier to just include you job classes here.
    # So, something like this:
    require 'jobs'
  end

  task :scheduler => :setup_schedule
end
```

The scheduler rake task is responsible for both queueing items from the
schedule and polling the delayed queue for items ready to be pushed on
to the work queues.  For obvious reasons, this process never exits.

``` bash
rake resque:scheduler
```

or, if you want to load the environment first:

``` bash
rake environment resque:scheduler
```


### Standalone Executable

The scheduler may also be run via a standalone `resque-scheduler`
executable, which will be available once the gem is installed.

``` bash
# Get some help
resque-scheduler --help
```

The executable accepts options via option flags as well as via
[environment variables](#environment-variables).

### Environment Variables

Both the Rake task and standalone executable support the following
environment variables:

* `APP_NAME` - Application name used in procline (`$0`) (default empty)
* `BACKGROUND` - [Run in the background](#running-in-the-background) if
non-empty (via `Process.daemon`, if supported) (default `false`)
* `DYNAMIC_SCHEDULE` - Enables [dynamic scheduling](#dynamic-schedules)
if non-empty (default `false`)
* `RAILS_ENV` - Environment to use in procline (`$0`) (default empty)
* `INITIALIZER_PATH` - Path to a Ruby file that will be loaded *before*
requiring `resque` and `resque/scheduler` (default empty).
* `RESQUE_SCHEDULER_INTERVAL` - Interval in seconds for checking if a
scheduled job must run (coerced with `Kernel#Float()`) (default `5`)
* `LOGFILE` - Log file name (default empty, meaning `$stdout`)
* `LOGFORMAT` - Log output format to use (either `'text'` or `'json'`,
default `'text'`)
* `PIDFILE` - If non-empty, write process PID to file (default empty)
* `QUIET` - Silence most output if non-empty (equivalent to a level of
`MonoLogger::FATAL`, default `false`)
* `VERBOSE` - Maximize log verbosity if non-empty (equivalent to a level
of `MonoLogger::DEBUG`, default `false`)


### Resque Pool integration

For normal work with the
[resque-pool](https://github.com/nevans/resque-pool) gem, add the
following task to wherever tasks are kept, such as
`./lib/tasks/resque.rake`:

```ruby
task 'resque:pool:setup' do
  Resque::Pool.after_prefork do |job|
    Resque.redis.client.reconnect
  end
end
```


### Delayed jobs

Delayed jobs are one-off jobs that you want to be put into a queue at some point
in the future.  The classic example is sending email:

```ruby
Resque.enqueue_in(
  5.days,
  SendFollowUpEmail,
  user_id: current_user.id
)
```

This will store the job for 5 days in the resque delayed queue at which time
the scheduler process will pull it from the delayed queue and put it in the
appropriate work queue for the given job and it will be processed as soon as
a worker is available (just like any other resque job).

**NOTE**: The job does not fire **exactly** at the time supplied.  Rather, once that
time is in the past, the job moves from the delayed queue to the actual resque
work queue and will be completed as workers are free to process it.

Also supported is `Resque.enqueue_at` which takes a timestamp to queue the
job, and `Resque.enqueue_at_with_queue` which takes both a timestamp and a
queue name:

```ruby
Resque.enqueue_at_with_queue(
  'queue_name',
  5.days.from_now,
  SendFollowUpEmail,
  user_id: current_user.id
)
```

The delayed queue is stored in redis and is persisted in the same way the
standard resque jobs are persisted (redis writing to disk). Delayed jobs differ
from scheduled jobs in that if your scheduler process is down or workers are
down when a particular job is supposed to be queue, they will simply "catch up"
once they are started again.  Jobs are guaranteed to run (provided they make it
into the delayed queue) after their given `queue_at` time has passed.

One other thing to note is that insertion into the delayed queue is O(log(n))
since the jobs are stored in a redis sorted set (zset).  I can't imagine this
being an issue for someone since redis is stupidly fast even at log(n), but full
disclosure is always best.

#### Removing Delayed jobs

If you have the need to cancel a delayed job, you can do like so:

```ruby
# after you've enqueued a job like:
Resque.enqueue_at(5.days.from_now, SendFollowUpEmail, :user_id => current_user.id)
# remove the job with exactly the same parameters:
Resque.remove_delayed(SendFollowUpEmail, :user_id => current_user.id)
```

If you need to cancel a delayed job based on some matching arguments, but don't wish to specify each argument from when the job was created, you can do like so:

``` ruby
# after you've enqueued a job like:
Resque.enqueue_at(5.days.from_now, SendFollowUpEmail, :account_id => current_account.id, :user_id => current_user.id)
# remove jobs matching just the account:
Resque.remove_delayed_selection { |args| args[0]['account_id'] == current_account.id }
# or remove jobs matching just the user:
Resque.remove_delayed_selection { |args| args[0]['user_id'] == current_user.id }
```

If you need to enqueue immediately a delayed job based on some matching arguments, but don't wish to specify each argument from when the job was created, you can do like so:

``` ruby
# after you've enqueued a job like:
Resque.enqueue_at(5.days.from_now, SendFollowUpEmail, :account_id => current_account.id, :user_id => current_user.id)
# enqueue immediately jobs matching just the account:
Resque.enqueue_delayed_selection { |args| args[0]['account_id'] == current_account.id }
# or enqueue immediately jobs matching just the user:
Resque.enqueue_delayed_selection { |args| args[0]['user_id'] == current_user.id }
```

### Scheduled Jobs (Recurring Jobs)

Scheduled (or recurring) jobs are logically no different than a standard cron
job.  They are jobs that run based on a schedule which can be static or dynamic.

#### Static schedules

Static schedules are set when `resque-scheduler` starts by passing a schedule file
to `resque-scheduler` initialization like this (see *Installation* above for a more complete example):

```ruby
Resque.schedule = YAML.load_file('your_resque_schedule.yml')
```

If a static schedule is not set `resque-scheduler` will issue a "Schedule empty!" warning on
startup, but despite that warning setting a static schedule is totally optional. It is possible
to use only dynamic schedules (see below).

The schedule file is a list of Resque job classes with arguments and a
schedule frequency (in crontab syntax).  The schedule is just a hash, but
is usually stored in a YAML like this:

```yaml
CancelAbandonedOrders:
  cron: "*/5 * * * *"

queue_documents_for_indexing:
  cron: "0 0 * * *"
  # you can use rufus-scheduler "every" syntax in place of cron if you prefer
  # every: 1h
  # By default the job name (hash key) will be taken as worker class name.
  # If you want to have a different job name and class name, provide the 'class' option
  class: "QueueDocuments"
  queue: high
  args:
  description: "This job queues all content for indexing in solr"

clear_leaderboards_contributors:
  cron: "30 6 * * 1"
  class: "ClearLeaderboards"
  queue: low
  args: contributors
  description: "This job resets the weekly leaderboard for contributions"
```

If you would like to setup a job that is executed manually you can configure like this in your YAML file.

```yaml
ImportOrdersManual:
  description: 'Import Amazon Orders Manual'
  custom_job_class: 'AmazonMws::ImportOrdersJob'
  never: "* * * * *"
  queue: high
  description: "This is a manual job for importing orders."
  args:
    days_in_arrears: 7
```

The queue value is optional, but if left unspecified resque-scheduler will
attempt to get the queue from the job class, which means it needs to be
defined.  If you're getting "uninitialized constant" errors, you probably
need to either set the queue in the schedule or require your jobs in your
"resque:setup" rake task.

You can provide options to "every" or "cron" via Array:

```yaml
clear_leaderboards_moderator:
  every:
    - "30s"
    - :first_in: '120s'
  class: "CheckDaemon"
  queue: daemons
  description: "This job will check Daemon every 30 seconds after 120 seconds after start"
```

IMPORTANT: Rufus `every` syntax will calculate jobs scheduling time starting from the moment of deploy,
resulting in resetting schedule time on every deploy, so it's probably a good idea to use it only for
frequent jobs (like every 10-30 minutes), otherwise - when you use something like `every 20h` and deploy once-twice per day -
it will schedule the job for 20 hours from deploy, resulting in a job to never be run.

**NOTE**: Six parameter cron's are also supported (as they supported by
rufus-scheduler which powers the resque-scheduler process).  This allows you
to schedule jobs per second (ie: `"30 * * * * *"` would fire a job every 30
seconds past the minute).

A big shout out to [rufus-scheduler](http://github.com/jmettraux/rufus-scheduler)
for handling the heavy lifting of the actual scheduling engine.

#### Dynamic schedules

Dynamic schedules are programmatically set on a running `resque-scheduler`.
All [rufus-scheduler](http://github.com/jmettraux/rufus-scheduler) options are supported
when setting schedules.

Dynamic schedules are not enabled by default. To be able to dynamically set schedules, you
must pass the following to `resque-scheduler` initialization (see *Installation* above for a more complete example):

```ruby
Resque::Scheduler.dynamic = true
```

**NOTE**: In order to delete dynamic schedules via `resque-web` in the
"Schedule" tab, you must include the `Rack::MethodOverride` middleware (in
`config.ru` or equivalent).

Dynamic schedules allow for greater flexibility than static schedules as they can be set,
unset or changed without having to restart `resque-scheduler`. You can specify, if the schedule
must survive a resque-scheduler restart or not. This is done by setting the `persist` configuration
for the schedule: it is a boolean value, if set the schedule will persist a restart. By default,
a schedule will not be persisted.

The job to be scheduled must be a valid Resque job class.

For example, suppose you have a SendEmail job which sends emails. The `perform` method of the
job receives a string argument with the email subject. To run the SendEmail job every hour
starting five minutes from now, you can do:

```ruby
name = 'send_emails'
config = {}
config[:class] = 'SendEmail'
config[:args] = 'POC email subject'
config[:every] = ['1h', {first_in: 5.minutes}]
config[:persist] = true
Resque.set_schedule(name, config)
```

Schedules can later be removed by passing their name to the `remove_schedule` method:

```ruby
name = 'send_emails'
Resque.remove_schedule(name)
```

Schedule names are unique; i.e. two dynamic schedules cannot have the same name. If `set_schedule` is
passed the name of an existing schedule, that schedule is updated. E.g. if after setting the above schedule
 we want the job to run every day instead of every hour from now on, we can do:

```ruby
name = 'send_emails'
config = {}
config[:class] = 'SendEmail'
config[:args] = 'POC email subject'
config[:every] = '1d'
Resque.set_schedule(name, config)
```

#### Time zones

Note that if you use the cron syntax, this will be interpreted as in the server time zone
rather than the `config.time_zone` specified in Rails.

You can explicitly specify the time zone that rufus-scheduler will use:

```yaml
cron: "30 6 * * 1 Europe/Stockholm"
```

Also note that `config.time_zone` in Rails allows for a shorthand (e.g. "Stockholm")
that rufus-scheduler does not accept. If you write code to set the scheduler time zone
from the `config.time_zone` value, make sure it's the right format, e.g. with:

```ruby
ActiveSupport::TimeZone.find_tzinfo(Rails.configuration.time_zone).name
```

A future version of resque-scheduler may do this for you.

#### Hooks

Similar to the `before_enqueue`- and `after_enqueue`-hooks provided in Resque
(>= 1.19.1), your jobs can specify one or more of the following hooks:

* `before_schedule`: Called with the job args before a job is placed on
  the delayed queue. If the hook returns `false`, the job will not be placed on
  the queue.
* `after_schedule`: Called with the job args after a job is placed on the
  delayed queue. Any exception raised propagates up to the code with queued the
  job.
* `before_delayed_enqueue`: Called with the job args after the job has been
  removed from the delayed queue, but not yet put on a normal queue. It is
  called before `before_enqueue`-hooks, and on the same job instance as the
  `before_enqueue`-hooks will be invoked on. Return values are ignored.
* `on_enqueue_failure`: Called with the job args and the exception that was raised
  while enqueueing a job to resque or external application fails.  Return
  values are ignored. For example:

  ```ruby
  Resque::Scheduler.failure_handler = ExceptionHandlerClass
  ```

#### Support for resque-status (and other custom jobs)

Some Resque extensions like
[resque-status](http://github.com/quirkey/resque-status) use custom job
classes with a slightly different API signature.  Resque-scheduler isn't
trying to support all existing and future custom job classes, instead it
supports a schedule flag so you can extend your custom class and make it
support scheduled job.

Let's pretend we have a `JobWithStatus` class called `FakeLeaderboard`

```ruby
class FakeLeaderboard < Resque::JobWithStatus
  def perform
    # do something and keep track of the status
  end
end
```

And then a schedule:

```yaml
create_fake_leaderboards:
  cron: "30 6 * * 1"
  queue: scoring
  custom_job_class: "FakeLeaderboard"
  args:
  rails_env: demo
  description: "This job will auto-create leaderboards for our online demo and the status will update as the worker makes progress"
```

If your extension doesn't support scheduled job, you would need to extend the
custom job class to support the #scheduled method:

```ruby
module Resque
  class JobWithStatus
    # Wrapper API to forward a Resque::Job creation API call into
    # a JobWithStatus call.
    def self.scheduled(queue, klass, *args)
      create(*args)
    end
  end
end
```

### Redundancy and Fail-Over

*>= 2.0.1 only.  Prior to 2.0.1, it is not recommended to run multiple resque-scheduler processes and will result in duplicate jobs.*

You may want to have resque-scheduler running on multiple machines for
redundancy.  Electing a master and failover is built in and default.  Simply
run resque-scheduler on as many machine as you want pointing to the same
redis instance and schedule.  The scheduler processes will use redis to
elect a master process and detect failover when the master dies.  Precautions are
taken to prevent jobs from potentially being queued twice during failover even
when the clocks of the scheduler machines are slightly out of sync (or load affects
scheduled job firing time).  If you want the gory details, look at Resque::Scheduler::Locking.

If the scheduler process(es) goes down for whatever reason, the delayed items
that should have fired during the outage will fire once the scheduler process
is started back up again (regardless of it being on a new machine).  Missed
scheduled jobs, however, will not fire upon recovery of the scheduler process.
Think of scheduled (recurring) jobs as cron jobs - if you stop cron, it doesn't fire
missed jobs once it starts back up.

You might want to share a redis instance amongst multiple Rails applications with different
scheduler with different config yaml files. If this is the case, normally, only one will ever
run, leading to undesired behaviour. To allow different scheduler configs run at the same time
on one redis, you can either namespace your redis connections, or supply an environment variable
to split the shared lock key resque-scheduler uses thus:

``` bash
RESQUE_SCHEDULER_MASTER_LOCK_PREFIX=MyApp: rake resque:scheduler
```

### resque-web Additions

Resque-scheduler also adds to tabs to the resque-web UI.  One is for viewing
(and manually queueing) the schedule and one is for viewing pending jobs in
the delayed queue.

The Schedule tab:

![The Schedule Tab](https://f.cloud.github.com/assets/45143/1178456/c99e5568-21b0-11e3-8c57-e1305d0ee8ef.png)

The Delayed tab:

![The Delayed Tab](http://img.skitch.com/20100111-ne4fcqtc5emkcuwc5qtais2kwx.jpg)

#### How do I get the schedule tabs to show up???

To get these to show up you need to pass a file to `resque-web` to tell it to
include the `resque-scheduler` plugin and the resque-schedule server extension
to the resque-web sinatra app.  Unless you're running redis on localhost, you
probably already have this file.  It probably looks something like this:

```ruby
require 'resque' # include resque so we can configure it
Resque.redis = "redis_server:6379" # tell Resque where redis lives
```

Now, you want to add the following:

```ruby
# This will make the tabs show up.
require 'resque-scheduler'
require 'resque/scheduler/server'
```

That should make the scheduler tabs show up in `resque-web`.

#### Changes as of 2.0.0

As of resque-scheduler 2.0.0, it's no longer necessary to have the resque-web
process aware of the schedule because it reads it from redis.  But prior to
2.0, you'll want to make sure you load the schedule in this file as well.
Something like this:

```ruby
Resque.schedule = YAML.load_file(File.join(RAILS_ROOT, 'config/resque_schedule.yml')) # load the schedule
```

Now make sure you're passing that file to resque-web like so:

    resque-web ~/yourapp/config/resque_config.rb


### Running in the background

(Only supported with ruby >= 1.9). There are scenarios where it's helpful for
the resque worker to run itself in the background (usually in combination with
PIDFILE).  Use the BACKGROUND option so that rake will return as soon as the
worker is started.

    $ PIDFILE=./resque-scheduler.pid BACKGROUND=yes \
        rake resque:scheduler


### Logging

There are several options to toggle the way scheduler logs its actions. They
are toggled by environment variables:

  - `QUIET` will stop logging anything. Completely silent.
  - `VERBOSE` opposite of 'QUIET'; will log even debug information
  - `LOGFILE` specifies the file to write logs to. (default standard output)
  - `LOGFORMAT` specifies either "text" or "json" output format
    (default "text")

All of these variables are optional and will be given the following default
values:

```ruby
Resque::Scheduler.configure do |c|
  c.quiet = false
  c.verbose = false
  c.logfile = nil # meaning all messages go to $stdout
  c.logformat = 'text'
end
```

### Polling frequency

You can pass a `RESQUE_SCHEDULER_INTERVAL` option which is an integer or
float representing the polling frequency. The default is 5 seconds, but
for a semi-active app you may want to use a smaller value.

    $ RESQUE_SCHEDULER_INTERVAL=1 rake resque:scheduler

**NOTE** This value was previously `INTERVAL` but was renamed to
`RESQUE_SCHEDULER_INTERVAL` to avoid clashing with the interval Resque
uses for its jobs.

### Plagiarism alert

This was intended to be an extension to resque and so resulted in a lot
of the code looking very similar to resque, particularly in resque-web
and the views. I wanted it to be similar enough that someone familiar
with resque could easily work on resque-scheduler.

### Development

Working on resque-scheduler requires the following:

* A relatively modern Ruby interpreter
* bundler

The development setup looks like this, which is roughly the same thing
that happens on Travis CI and Appveyor:

``` bash
# Install everything
bundle install

# Make sure tests are green before you change stuff
bundle exec rake
# Change stuff
# Repeat
```

If you have [vagrant](http://www.vagrantup.com) installed, there is a
development box available that requires no plugins or external
provisioners:

``` bash
vagrant up
```

### Deployment Notes

It is recommended that a production deployment of `resque-scheduler` be hosted
on a dedicated Redis database.  While making and managing scheduled tasks,
`resque-scheduler` currently scans the entire Redis keyspace, which may cause
latency and stability issues if `resque-scheduler` is hosted on a Redis instance
storing a large number of keys (such as those written by a different system
hosted on the same Redis instance).

#### Compatibility Notes

Different versions of the `redis` and `rufus-scheduler` gems are needed
depending on your version of `resque-scheduler`.  This is typically not a
problem with `resque-scheduler` itself, but when mixing dependencies with an
existing application.

This table explains the version requirements for redis gem

| resque-scheduler | redis gem  |
|:-----------------|-----------:|
| `~> 2.0`         | `>= 3.0.0` |
| `>= 0.0.1`       | `~> 1.3`   |

This table explains the version requirements for rufus-scheduler

| resque-scheduler | rufus-scheduler |
|:-----------------|----------------:|
| `~> 4.0`         | `~> 3.0`        |
| `< 4.0`          | `~> 2.0`        |


### Contributing

See [CONTRIBUTING.md](CONTRIBUTING.md)

### Authors

See [AUTHORS.md](AUTHORS.md)

### License

See [LICENSE](LICENSE)