simple_circuit_breaker.rb

## following is a simple cicruit breaker implementation with thread support.
## https://github.com/soundcloud/simple_circuit_breaker/blob/master/lib/simple_circuit_breaker.rb
class CircuitBreaker
  class Error < StandardError
  end

  def initialize(retry_timeout=10, threshold=30)
    @mutex = Mutex.new
    @retry_timeout = retry_timeout
    @threshold = threshold
    reset!
  end

  def handle
    if tripped?
      raise CircuitBreaker::Error.new('circuit opened')
    else
      execute
    end
  end

  def execute
    result = yield
    reset!
    result
    rescue Exception => exception
      fail!  
    raise exception
  end

  def tripped?
    opened? && !timeout_exceeded?
  end

  def fail!
    @mutex.synchronize do
      @failures += 1
      if @failures >= @threshold
        @open_time = Time.now
        @circuit = :opened
      end
    end
  end

  def opened?
    @circuit == :opened
  end

  def timeout_exceeded?
    @open_time + @retry_timeout < Time.now
  end

  def reset!
    @mutex.synchronize do 
      @circuit = :closed
      @failures = 0
    end
  end
end

http_circuit_breaker = CircuitBreaker.new
http_circuit_breaker.handle { make_http_request }