Simple Circuit Breaker Pattern in Ruby

This gem implements a very simple class to deal with the Circuit Breaker Pattern as described by Michael T. Nygard in his amazing and highly recommended Release It! - Design and Deploy Production-Ready Software.

Usage

require "disyuntor"

# Trip circuit after 10 errors
# Wait 5 seconds before trying again
disyuntor = Disyuntor.new(threshold: 10, timeout: 5)

res = disyuntor.try do
  # …your potentially failing operation…
end

A Disyuntor, or circuit breaker, has two (and a half) possible states:

• #closed? for when the protection hasn't detected any issues and your code is allowed to run;
• #open? for when the protection has reached a threshold of issues and your code won't be allowed to run.

The third, or rather second and a half state, is for when the circuit was open and timeout seconds passed. In this state your code is allowed to run just once. If it works without raising any new failure, then the circuit will automatically close itself until, otherwise it will remain in an open state for a new timeout interval in seconds.

Custom actions when circuit is open

By default, when the circuit is open, Disyuntor#try will fail with a Disyuntor::CircuitOpenError. This behavior can be changed by passing a Proc in the on_circuit_open option or method.

Every time the circuit is open, the #on_circuit_open method is called, passing the circuit as its argument. This allows customizing the failure mode of your circuit:

disyuntor = Disyuntor.new(threshold: 3, timeout: 5)

disyuntor.on_circuit_open do |c|
  puts "Ooops, can't execute circuit"
end

The value of the block will be returned as the value of Disyuntor#try when it fails.