Note: This is a complete piece of software, it should work across all future sidekiq & ruby versions.

Redis-based simple locking mechanism for sidekiq. Uses SET command introduced in Redis 2.6.16.

It can be handy if you push a lot of jobs into the queue(s), but you don't want to execute specific jobs at the same time - it provides a lock method that you can use in whatever way you want.

This gem requires at least:

• redis 2.6.12
• sidekiq 6

Add this line to your application's Gemfile:

gem 'sidekiq-lock'

And then execute:

$ bundle

Sidekiq-lock is a middleware/module combination, let me go through my thought process here :).

In your worker class include Sidekiq::Lock::Worker module and provide lock attribute inside sidekiq_options, for example:

class Worker
  include Sidekiq::Worker
  include Sidekiq::Lock::Worker

  # static lock that expires after one second
  sidekiq_options lock: { timeout: 1000, name: 'lock-worker' }

  def perform
    # ...
  end
end

What will happen is:

• middleware will setup a Sidekiq::Lock::RedisLock object under Thread.current[Sidekiq::Lock::THREAD_KEY] (it should work in most use cases without any problems - but it's configurable, more below) - assuming you provided lock options, otherwise it will do nothing, just execute your worker's code

• Sidekiq::Lock::Worker module provides a lock method that just simply points to that thread variable, just as a convenience

So now in your worker class you can call (whenever you need):

• lock.acquire! - will try to acquire the lock, if returns false on failure (that means some other process / thread took the lock first)
• lock.acquired? - set to true when lock is successfully acquired
• lock.release! - deletes the lock (only if it's: acquired by current thread and not already expired)

sidekiq_options lock will accept static values or Proc that will be called on argument(s) passed to perform method.

• timeout - specified expire time, in milliseconds
• name - name of the redis key that will be used as lock name
• value - (optional) value of the lock, if not provided it's set to random hex

Dynamic lock example:

class Worker
  include Sidekiq::Worker
  include Sidekiq::Lock::Worker
  sidekiq_options lock: {
    timeout: proc { |user_id, timeout| timeout * 2 },
    name:    proc { |user_id, timeout| "lock:peruser:#{user_id}" },
    value:   proc { |user_id, timeout| "#{user_id}" }
  }

  def perform(user_id, timeout)
    # ...
    # do some work
    # only at this point I want to acquire the lock
    if lock.acquire!
      begin
        # I can do the work
        # ...
      ensure
        # You probably want to manually release lock after work is done
        # This method can be safely called even if lock wasn't acquired
        # by current worker (thread). For more references see RedisLock class
        lock.release!
      end
    else
      # reschedule, raise an error or do whatever you want
    end
  end
end

Just be sure to provide valid redis key as a lock name.

You can change lock to something else (globally) in sidekiq server configuration:

Sidekiq.configure_server do |config|
  config.lock_method = :redis_lock
end

If you would like to change default behavior of storing lock instance in Thread.current for whatever reason you can do that as well via server configuration:

# Any thread-safe class that implements .fetch and .store methods will do
class CustomStorage
  def fetch
    # returns stored lock instance
  end
  
  def store(lock_instance)
    # store lock
  end
end

Sidekiq.configure_server do |config|
  config.lock_container = CustomStorage.new
end

As you know middleware is not invoked when testing jobs inline, you can require in your test/spec helper file sidekiq/lock/testing/inline to include two methods that will help you setting / clearing up lock manually:

• set_sidekiq_lock(worker_class, payload) - note: payload should be an array of worker arguments
• clear_sidekiq_lock

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