hobble

Ruby debt-based scheduling implementation.

Aim: Schedule a collection of grouped items in a way that is perceived to be fair.

Installation

Hobble is available as a gem, so simply run:

$ gem install hobble

Alternatively, you can add hobble to your Gemfile:

gem 'hobble'

Followed by:

$ bundle install

Usage

# Schedule some peoples' tasks:
@hobble = Hobble.schedule({
  jack: [:task1, :task2],
  john: [:task1, :task2, :task3]
})

# Add some more:
@hobble.schedule({
  jill: [:task3, :task1]
})

# Now run them fairly:
@hobble.run do |user, tasks|
  Task.process(tasks.shift, for: user)
end

Here, each user's queue (a Hobble::Collection) maintains a counter of how much time has been devoted to running that user's tasks.

Alternatively, you can specify the items using a block, which is re-evaluated after each item is run:

@hobble = Hobble.schedule { Tasks.pending.group_by(&:user) }

# Once a minute, run all pending tasks:
loop do
  puts 'Running all pending tasks...'
  @hobble.run do |user, tasks|
    Task.process(tasks.shift, for: user)
  end

  puts 'Waiting for more tasks...'
  sleep(60)
end

Processing time is made available to the pending collection with the least accrued time. The sort is not stable, to encourage variation in the case of a tie.

If necessary, it is possible to weight different users to accrue time differently:

# Have `jack` burn time at twice the default rate, and `jill` accrue at a quarter rate:
@hobble.weight!({
  jack: 2,
  jill: 0.25
})

When there are no matching collections, hobble's work is done!