class

CircuitBreaker

Inherits Reference < Object

Simple Implementation of the circuit breaker pattern in Crystal.

Given a certain error threshold, timeframe and timeout window, a breaker can be used to monitor criticial command executions. Circuit breakers are usually used to prevent unnecessary requests if a server ressource et al becomes unavailable. This protects the server from additional load and allows it to recover and relieves the client from requests that are doomed to fail.

Wrap API calls inside a breaker, if the error rate in a given time frame surpasses a certain threshold, all subsequent calls will fail for a given duration.

Constructors

new(threshold error_threshold : Int32, timewindow timeframe, reenable_after duration : Int32, handled_errors = [] of Exception, ignored_errors = [] of Exception)

creates a CircuitBreaker instance with a specified error threshold, timeframe, breaker duration and optionally a number of ignored or handled errors

breaker = CircuitBreaker.new(
  threshold: 5, # % of errors before you want to trip the circuit
  timewindow: 60, # in s: anything older will be ignored in error_rate
  reenable_after: 300 # after x seconds, the breaker will allow executions again
)

Source

Instance methods

run

get's passed a block to watch for errors every error thrown inside your block counts towards the error rate once the threshold is surpassed, it starts throwing CircuitOpenExceptions you can catch these rrors and implement some fallback behaviour

begin
  breaker.run do
    my_rest_call()
  end
rescue exc : CircuitOpenException
  log "happens to the best of us..."
  42
end

Source