= Sidekiq::Throttled
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****
{ci-link}[image:{ci-badge}[CI Status]]
{gem-link}[image:{gem-badge}[Latest Version]]
{doc-link}[image:{doc-badge}[API Documentation]]
****

Concurrency and threshold throttling for https://github.com/sidekiq/sidekiq[Sidekiq].

== Installation

Add this line to your application's Gemfile:

[source,ruby]
----
gem "sidekiq-throttled"
----

And then execute:

  $ bundle

Or install it yourself as:

  $ gem install sidekiq-throttled


== Usage

Add somewhere in your app's bootstrap (e.g. `config/initializers/sidekiq.rb` if
you are using Rails):

[source,ruby]
----
require "sidekiq/throttled"
----

Once you've done that you can include `Sidekiq::Throttled::Job` to your
job classes and configure throttling:

[source,ruby]
----
class MyJob
  include Sidekiq::Job
  include Sidekiq::Throttled::Job

  sidekiq_options :queue => :my_queue

  sidekiq_throttle(
    # Allow maximum 10 concurrent jobs of this class at a time.
    concurrency: { limit: 10 },
    # Allow maximum 1K jobs being processed within one hour window.
    threshold: { limit: 1_000, period: 1.hour }
  )

  def perform
    # ...
  end
end
----

TIP: `Sidekiq::Throttled::Job` is aliased as `Sidekiq::Throttled::Worker`,
  thus if you're using `Sidekiq::Worker` naming convention, you can use the
  alias for consistency:

[source,ruby]
----
class MyWorker
  include Sidekiq::Worker
  include Sidekiq::Throttled::Worker

  # ...
end
----


=== Configuration

[source,ruby]
----
Sidekiq::Throttled.configure do |config|
  # Period in seconds to exclude queue from polling in case it returned
  # {config.cooldown_threshold} amount of throttled jobs in a row. Set
  # this value to `nil` to disable cooldown manager completely.
  # Default: 2.0
  config.cooldown_period = 2.0

  # Exclude queue from polling after it returned given amount of throttled
  # jobs in a row.
  # Default: 1 (cooldown after first throttled job)
  config.cooldown_threshold = 1
end
----


==== Middleware(s)

`Sidekiq::Throttled` relies on following bundled middlewares:

* `Sidekiq::Throttled::Middlewares::Server`

The middleware is automatically injected when you require `sidekiq/throttled`.
In rare cases this might be an issue. You can change to order manually:

[source,ruby]
----
Sidekiq.configure_server do |config|
  # ...

  config.server_middleware do |chain|
    chain.remove(Sidekiq::Throttled::Middlewares::Server)
    chain.add(Sidekiq::Throttled::Middlewares::Server)
  end
end
----

See: https://github.com/sidekiq/sidekiq/blob/main/lib/sidekiq/middleware/chain.rb


=== Observer

You can specify an observer that will be called on throttling. To do so pass an
`:observer` option with callable object:

[source,ruby]
----
class MyJob
  include Sidekiq::Job
  include Sidekiq::Throttled::Job

  MY_OBSERVER = lambda do |strategy, *args|
    # do something
  end

  sidekiq_options queue: :my_queue

  sidekiq_throttle(
    concurrency: { limit: 10 },
    threshold:   { limit: 100, period: 1.hour },
    observer:    MY_OBSERVER
  )

  def perform(*args)
    # ...
  end
end
----

Observer will receive `strategy, *args` arguments, where `strategy` is a Symbol
`:concurrency` or `:threshold`, and `*args` are the arguments that were passed
to the job.


=== Dynamic throttling

You can throttle jobs dynamically with `:key_suffix` option:

[source,ruby]
----
class MyJob
  include Sidekiq::Job
  include Sidekiq::Throttled::Job

  sidekiq_options queue: :my_queue

  sidekiq_throttle(
    # Allow maximum 10 concurrent jobs per user at a time.
    concurrency: { limit: 10, key_suffix: -> (user_id) { user_id } }
  )

  def perform(user_id)
    # ...
  end
end
----

You can also supply dynamic values for limits and periods by supplying a proc
for these values. The proc will be evaluated at the time the job is fetched
and will receive the same arguments that are passed to the job.

[source,ruby]
----
class MyJob
  include Sidekiq::Job
  include Sidekiq::Throttled::Job

  sidekiq_options queue: :my_queue

  sidekiq_throttle(
    # Allow maximum 1000 concurrent jobs of this class at a time for VIPs and 10 for all other users.
    concurrency: {
      limit:      ->(user_id) { User.vip?(user_id) ? 1_000 : 10 },
      key_suffix: ->(user_id) { User.vip?(user_id) ? "vip" : "std" }
    },
    # Allow 1000 jobs/hour to be processed for VIPs and 10/day for all others
    threshold: {
      limit:      ->(user_id) { User.vip?(user_id) ? 1_000 : 10 },
      period:     ->(user_id) { User.vip?(user_id) ? 1.hour : 1.day },
      key_suffix: ->(user_id) { User.vip?(user_id) ? "vip" : "std" }
    }
  )

  def perform(user_id)
    # ...
  end
end
----

You also can use several different keys to throttle one worker.

[source,ruby]
----
class MyJob
  include Sidekiq::Job
  include Sidekiq::Throttled::Job

  sidekiq_options queue: :my_queue

  sidekiq_throttle(
    # Allow maximum 10 concurrent jobs per project at a time and maximum 2 jobs per user
    concurrency: [
      { limit: 10, key_suffix: -> (project_id, user_id) { project_id } },
      { limit: 2, key_suffix: -> (project_id, user_id) { user_id } }
    ]
    # For :threshold it works the same
  )

  def perform(project_id, user_id)
    # ...
  end
end
----

IMPORTANT: Don't forget to specify `:key_suffix` and make it return different
  values if you are using dynamic limit/period options. Otherwise, you risk
  getting into some trouble.


=== Concurrency throttling fine-tuning

Concurrency throttling is based on distributed locks. Those locks have default
time to live (TTL) set to 15 minutes. If your job takes more than 15 minutes
to finish, lock will be released and you might end up with more jobs running
concurrently than you expect.

This is done to avoid deadlocks - when by any reason (e.g. Sidekiq process was
OOM-killed) cleanup middleware wasn't executed and locks were not released.

If your job takes more than 15 minutes to complete, you can tune concurrency
lock TTL to fit your needs:

[source,ruby]
----
# Set concurrency strategy lock TTL to 1 hour.
sidekiq_throttle(concurrency: { limit: 20, ttl: 1.hour.to_i })
----


== Supported Ruby Versions

This library aims to support and is tested against the following Ruby versions:

* Ruby 2.7.x
* Ruby 3.0.x
* Ruby 3.1.x
* Ruby 3.2.x

If something doesn't work on one of these versions, it's a bug.

This library may inadvertently work (or seem to work) on other Ruby versions,
however support will only be provided for the versions listed above.

If you would like this library to support another Ruby version or
implementation, you may volunteer to be a maintainer. Being a maintainer
entails making sure all tests run and pass on that implementation. When
something breaks on your implementation, you will be responsible for providing
patches in a timely fashion. If critical issues for a particular implementation
exist at the time of a major release, support for that Ruby version may be
dropped.


== Supported Sidekiq Versions

This library aims to support and work with following Sidekiq versions:

* Sidekiq 6.5.x
* Sidekiq 7.0.x
* Sidekiq 7.1.x
* Sidekiq 7.2.x


== Development

  bundle install
  bundle exec appraisal generate
  bundle exec appraisal install
  bundle exec rake


== Contributing

* Fork sidekiq-throttled on GitHub
* Make your changes
* Ensure all tests pass (`bundle exec rake`)
* Send a pull request
* If we like them we'll merge them
* If we've accepted a patch, feel free to ask for commit access!


== Endorsement

https://github.com/sensortower[image:sensortower.svg[SensorTower]]

The initial work on the project was initiated to address the needs of
https://github.com/sensortower[SensorTower].