README.md
# Sucker Punch
[](https://github.com/brandonhilkert/sucker_punch/actions/workflows/build.yml)
[](https://codeclimate.com/github/brandonhilkert/sucker_punch)
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 # => #<Logger:0x007fa1f28b83f0>
```
_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