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Deferrer

Deferrer is a library for deferring work units for a time period or to a specific time. When time reaches, only the last work unit will be processed. Usually, the last work unit should be the one that summarizes all the previous ones. An example scenario would be sending live updates that happen very frequently and we want to limit them by sending an update every x seconds.

Installation

Add this line to your application's Gemfile:

gem 'deferrer'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install deferrer

Usage

Configure deferrer (redis connection, logger)

Deferrer.redis_config = { :host => "localhost", :port => 6379 }
Deferrer.logger = Logger.new(STDOUT)

Define deferrer worker that must respond to call method

Deferrer.worker = lambda do |klass, *args|
  # do some work
  # Resque.enqueue(klass, *args)
end

Deferrer is usually used in combination with background processing tools like sidekiq and resque. If that's the case, Deferrer.worker can be light-weight and responsible only for pushing work to a background job.

Start a worker process.

Deferrer.run(options = {})

# Following `options` are available:
#   loop_frequency - sleep between loops, default to 0.1 seconds
#   single_run     - process items only for a single loop, useful for testing
#   ignore_time    - don't wait for time period to expire, useful for testing

Defer some executions:

Deferrer.defer_in(5, 'identifier', Worker, 'update 1')
Deferrer.defer_in(6, 'identifier', Worker, 'update 2')
Deferrer.defer_in(9, 'identifier', Worker, 'update 3')

It will stack all defered executions per identifier until first timeout expires (5 seconds) and then it will only execute the last update for the expired identifier, calling the deferrer worker:

Deferrer.worker.call('Worker', 'update 3')

Testing

For testing, two options of the run method are useful. single_run will run the loop only once and ignore_time will not wait for time period to expire but execute to job now.

Deferrer.run(single_run: true, ignore_time: true)

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