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https://github.com/brandonhilkert/sucker_punch

Sucker Punch is a Ruby asynchronous processing library using concurrent-ruby, heavily influenced by Sidekiq and girl_friday.
https://github.com/brandonhilkert/sucker_punch

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Sucker Punch is a Ruby asynchronous processing library using concurrent-ruby, heavily influenced by Sidekiq and girl_friday.

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# Sucker Punch



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Sucker Punch is a single-process Ruby asynchronous processing library.

This reduces costs

of hosting on a service like Heroku along with the memory footprint of

having to maintain additional jobs if hosting on a dedicated server.

All queues can run within a single application (eg. Rails, Sinatra, etc.) process.



Sucker Punch is perfect for asynchronous processes like emailing, data

crunching, or social platform manipulation. No reason to hold up a

user when you can do these things in the background within the same

process as your web application...



Sucker Punch is built on top of [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby). Each job is setup as

a pool, which equates to its own queue with individual workers working against

the jobs. Unlike most other background processing libraries, Sucker

Punch's jobs are stored in memory. The benefit to this is there is no

additional infrastructure requirement (ie. database, redis, etc.). However,

if the web processes are restarted with jobs remaining in the queue,

they will be lost. For this reason, Sucker Punch is generally

recommended for jobs that are fast and non-mission critical (ie. logs, emails,

etc.).



## Installation



Add this line to your application's Gemfile:



    gem 'sucker_punch', '~> 3.0'



And then execute:



    $ bundle



You can also run (same as two steps above):



    bundle add sucker_punch



Or install it yourself as:



    $ gem install sucker_punch



## Backwards Compatibility



No breaking changes were introduced in version 3.x.



In version `~> 2.0.0`, the syntax to enqueue an asynchronous background job was changed from:



```ruby

LogJob.new.async.perform(...)

```



to:



```ruby

LogJob.perform_async(...)

```



If you're upgrading from a pre-`2.0.0` release and want to retain the old

syntax `LogJob.new.async.perform(...)`, you can include

`sucker_punch/async_syntax` in your application.



For Rails, you could add an initializer:



```ruby

# config/initializers/sucker_punch.rb



require 'sucker_punch/async_syntax'

```



## Usage



Each job acts as its own queue and should be a separate Ruby class that:



* includes `SuckerPunch::Job`

* defines the `perform` instance method that includes the code the job will run when enqueued



```Ruby

# app/jobs/log_job.rb



class LogJob

  include SuckerPunch::Job



  def perform(event)

    Log.new(event).track

  end

end

```



#### Synchronous



```Ruby

LogJob.new.perform("login")

```



#### Asynchronous



```Ruby

LogJob.perform_async("login")

```



#### Configure the # of the Workers



The default number of workers (threads) running against your job is `2`. If

you'd like to configure this manually, the number of workers can be

set on the job using the `workers` class method:



```Ruby

class LogJob

  include SuckerPunch::Job

  workers 4



  def perform(event)

    Log.new(event).track

  end

end

```



#### Configure the Queue Size



The default number of jobs that can be queued is unlimited. If you wish to restrict this you can set

max\_jobs as follows:



```Ruby

class LogJob

  include SuckerPunch::Job

  max_jobs 10



  def perform(event)

    Log.new(event).track

  end

end

```



#### Executing Jobs in the Future



Many background processing libraries have methods to perform operations after a

certain amount of time and Sucker Punch is no different. Use the `perform_in`

with an argument of the number of seconds in the future you would like the job

to job to run.



``` ruby

class DataJob

  include SuckerPunch::Job



  def perform(data)

    puts data

  end

end



DataJob.perform_async("asdf") # immediately perform asynchronously

DataJob.perform_in(60, "asdf") # `perform` will be executed 60 sec. later

```



#### `ActiveRecord` Connection Pool Connections



Jobs interacting with `ActiveRecord` should take special precaution not to

exhaust connections in the pool. This can be done

with `ActiveRecord::Base.connection_pool.with_connection`, which ensures

the connection is returned back to the pool when completed.



```Ruby

# app/jobs/awesome_job.rb



class AwesomeJob

  include SuckerPunch::Job



  def perform(user_id)

    ActiveRecord::Base.connection_pool.with_connection do

      user = User.find(user_id)

      user.update(is_awesome: true)

    end

  end

end

```



We can create a job from within another job:



```Ruby

class AwesomeJob

  include SuckerPunch::Job



  def perform(user_id)

    ActiveRecord::Base.connection_pool.with_connection do

      user = User.find(user_id)

      user.update_attributes(is_awesome: true)

      LogJob.perform_async("User #{user.id} became awesome!")

    end

  end

end

```



#### Logger



```Ruby

SuckerPunch.logger = Logger.new('sucker_punch.log')

SuckerPunch.logger # => #

```



_Note: If Sucker Punch is being used within a Rails application, Sucker Punch's logger

is set to Rails.logger by default._



#### Exceptions



You can customize how to handle uncaught exceptions that are raised by your jobs.



For example, using Rails and the ExceptionNotification gem,

add a new initializer `config/initializers/sucker_punch.rb`:



```Ruby

# ex    => The caught exception object

# klass => The job class

# args  => An array of the args passed to the job



SuckerPunch.exception_handler = -> (ex, klass, args) { ExceptionNotifier.notify_exception(ex) }

```



Or, using Airbrake:



```Ruby

SuckerPunch.exception_handler = -> (ex, klass, args) { Airbrake.notify(ex) }

```



#### Shutdown Timeout



Sucker Punch goes through a series of checks to attempt to shut down the queues

and their threads. A "shutdown" command is issued to the queues, which gives

them notice but allows them to attempt to finish all remaining jobs.

Subsequently enqueued jobs are discarded at this time.



The default `shutdown_timeout` (the # of seconds to wait before forcefully

killing the threads) is 8 sec. This is to allow applications hosted on Heroku

to attempt to shutdown prior to the 10 sec. they give an application to

shutdown with some buffer.



To configure something other than the default 8 sec.:



```ruby

  SuckerPunch.shutdown_timeout = 15 # # of sec. to wait before killing threads

```



#### Queue Class Methods



Sucker Punch leverages concurrent-friendly queues per-process. These class methods operating on all queues might be helpful in some edge cases.



- `SuckerPunch::Queue.stats` - Returns a hash keyed by each queue's name with total, busy, and timeout statistics for each queue's `workers` and `jobs`.

- `SuckerPunch::Queue.clear` - Calls `clear` for each queue. Susceptible to race conditions. Only use in testing.

- `SuckerPunch::Queue.shutdown_all` - Used with SuckerPunch's `at_exit` hook. Waits for all queues to be idle using the [shutdown timeout](#shutdown-timeout) configuration above.

- `SuckerPunch::Queue.wait` - Waits for all queues to become idle with no timeout. 



#### Timeouts



Using `Timeout` causes persistent connections to

[randomly get corrupted](http://www.mikeperham.com/2015/05/08/timeout-rubys-most-dangerous-api).

Do not use timeouts as control flow, use built-in connection timeouts.

If you decide to use Timeout, only use it as last resort to know something went very wrong and

ideally restart the worker process after every timeout.



## Testing



Requiring this library causes your jobs to run everything inline.

So a call to the following will actually be SYNCHRONOUS:



```Ruby

# spec/spec_helper.rb

require 'sucker_punch/testing/inline'

```



```Ruby

LogJob.perform_async("login") # => Will be synchronous and block until job is finished

```



## Rails



If you're using Sucker Punch with Rails, there's a built-in generator task:



```ruby

$ rails g sucker_punch:job logger

```



would create the file `app/jobs/logger_job.rb` with a unimplemented `#perform`

method.



## Sinatra



If you're using Sucker Punch with Sinatra, you must require Sucker Punch before Sinatra:



```ruby

# app.rb



require 'sucker_punch'

require 'sinatra'

```



This will ensure Sucker Punch's `at_exit()` handler to clean up and shutdown queues does not happen **before** Sinatra *starts up* via its own `at_exit()` handler.



## Active Job



Sucker Punch has been added as an Active Job adapter in Rails 4.2.

See the [guide](http://edgeguides.rubyonrails.org/active_job_basics.html) for

configuration and implementation.



Add Sucker Punch to your `Gemfile`:



```Ruby

gem 'sucker_punch'

```



And then configure the backend to use Sucker Punch:



```Ruby

# config/application.rb

class Application < Rails::Application

  # ...

  config.active_job.queue_adapter = :sucker_punch

end

```



If you want to use Sucker Punch version `2.0.0+` with Rails `< 5.0.0`, be sure

to include the backwards compatibility module in an initializer:



```ruby

# config/initializers/sucker_punch.rb



require 'sucker_punch/async_syntax'

```



## FAQ



**What is the difference between `sucker_punch` and `ActiveJob::QueueAdapters::AsyncAdapter`?**



Not much at this point. SuckerPunch existed before ActiveJob, but ultimately uses similar code under the covers. I'd recommend using `AsyncAdapter` if you're using Rails.



## Troubleshooting



### Initializers for forking servers (Unicorn, Passenger, etc.)



Previously, Sucker Punch required an initializer and that posed problems for

servers that fork (ie. Unicorn and Passenger). Version 1 was rewritten to

not require any special code to be executed after forking occurs. Please remove

 if you're using version `>= 1.0.0`



### Cleaning test data transactions



If you're running tests in transactions (using Database Cleaner or a native solution), Sucker Punch jobs may have trouble finding database records that were created during test setup because the job class is running in a separate thread and the Transaction operates on a different thread so it clears out the data before the job can do its business. The best thing to do is cleanup data created for tests jobs through a truncation strategy by tagging the rspec tests as jobs and then specifying the strategy in `spec_helper` like below. And do not forget to turn off transactional fixtures (delete, comment or set it to `false`).



```Ruby

# spec/spec_helper.rb

RSpec.configure do |config|



  # Turn off transactional fixtures (delete, comment or set it to `false`)

  # config.use_transactional_fixtures = true



  config.before(:each) do

    DatabaseCleaner.strategy = :transaction

  end



  # Clean up all jobs specs with truncation

  config.before(:each, job: true) do

    DatabaseCleaner.strategy = :truncation

  end



  config.before(:each) do

    DatabaseCleaner.start

  end



  config.after(:each) do

    DatabaseCleaner.clean

  end

end



# spec/jobs/email_job_spec.rb

require 'spec_helper'



# Tag the spec as a job spec so data is persisted long enough for the test

describe EmailJob, job: true do

  describe "#perform" do

    let(:user) { FactoryGirl.create(:user) }



    it "delivers an email" do

      expect {

        EmailJob.new.perform(user.id)

      }.to change{ ActionMailer::Base.deliveries.size }.by(1)

    end

  end

end

```



## Contributing



1. Fork it

2. Create your feature branch (`git checkout -b my-new-feature`)

3. Commit your changes (`git commit -am 'Add some feature'`)

4. Push to the branch (`git push origin my-new-feature`)

5. Create new Pull Request