Module: TResque::QueueLock

Included in:
DelayExecutionWorker
Defined in:
lib/tresque/queue_lock.rb

Overview

If you want only one instance of your job queued at a time, extend it with this module.

Instance Method Summary collapse

Instance Method Details

#after_dequeue_queue_lock(options) ⇒ Object 



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# File 'lib/tresque/queue_lock.rb', line 66

def after_dequeue_queue_lock(options)
  clear_queue_lock(options)
end

#before_enqueue_queue_lock(options) ⇒ Object

See the documentation for SETNX redis.io/commands/setnx for an explanation of this deadlock free locking pattern



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# File 'lib/tresque/queue_lock.rb', line 22

def before_enqueue_queue_lock(options)
  val = queue_lock_key(options)
  if val
    key = "lock:#{val}"
    now = Time.now.to_i
    from_now = queue_lock_timeout + 1
    key_expire = from_now + 600 # some exra time
    timeout = now + from_now

    # return true if we successfully acquired the lock
    if Resque.redis.setnx(key, timeout)
      # expire in case of error to make sure it goes away
      Resque.redis.expire(key, key_expire)
      return true
    end

    # see if the existing timeout is still valid and return false if it is
    # (we cannot acquire the lock during the timeout period)
    return false if now <= Resque.redis.get(key).to_i

    # otherwise set the timeout and ensure that no other worker has
    # acquired the lock
    if now > Resque.redis.getset(key, timeout).to_i
      # expire in case of error to make sure it goes away
      Resque.redis.expire(key, key_expire)
      return true
    else
      return false
    end

  end
end

#before_perform_queue_lock(options) ⇒ Object 



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# File 'lib/tresque/queue_lock.rb', line 62

def before_perform_queue_lock(options)
  clear_queue_lock(options)
end

#clear_queue_lock(options) ⇒ Object 



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# File 'lib/tresque/queue_lock.rb', line 55

def clear_queue_lock(options)
  val = queue_lock_key(options)
  if val
    Resque.redis.del("lock:#{val}")
  end
end

#queue_lock_timeout ⇒ Object

Override in your job to control the lock experiation time. This is the time in seconds that the lock should be considered valid. The default is one hour (3600 seconds).



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# File 'lib/tresque/queue_lock.rb', line 9

def queue_lock_timeout
  3600
end