Basic circuit breaker in Ruby

breaker.rb

class Breaker
  def initialize(threshold, debug = false)
    @active = true
    @fails = 0
    @threshold = threshold
    @debug = debug
    @on_trip = nil
  end

  def on_trip(&block)
    @on_trip = block
  end

  def pass
    @active = true
    @fails = 0
    debug
  end

  def fail
    @fails += 1
    debug
    check_break
  end

  private

  def check_break
    return unless @active
    return if @fails < @threshold
    @active = false
    @on_trip.call if @on_trip
  end

  def debug
    puts "Breaker: #{@active ? 'active' : 'tripped'}, #{@fails}/#{@threshold} fails" if @debug
  end
end

test_breaker.rb

require_relative 'breaker'

b = Breaker.new(3, debug: true)
b.on_trip do
  puts 'Tripped!'
end
b.pass
b.pass
b.fail
b.fail
b.fail  # Tripped!
b.pass
b.pass
b.fail
b.pass
b.pass
b.fail
b.fail
b.fail  # Tripped!
b.fail
b.fail