Circuit Breaker

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# Logic based on https://martinfowler.com/bliki/CircuitBreaker.html
class CircuitBreaker < ApplicationRecord
  ERROR_THRESHOLD = 5
  RESET_TIMEOUT = 5.minutes

  # name, error_count, last_error_at
  def state
    if error_count < ERROR_THRESHOLD
      :ok
    elsif last_error_at < RESET_TIMEOUT.ago
      :recoverable
    else
      :error
    end
  end

  def call(primary, alternate, recoverable_errors = [StandardError])
    if state == :error
      alternate.call
    else # :ok, :recoverable
      begin
        primary.call.tap { record_success }
      rescue *recoverable_errors => exception
        Sentry.capture_exception(exception)
        record_failure
        alternate.call
      end
    end
  end

  private

  def record_success
    update(error_count: 0) if error_count > 0
  end

  def record_failure
    update(error_count: error_count + 1, last_error_at: Time.current)
  end
end

About

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Jamie Macey is a senior software engineer with over 15 years experience in the Ruby and Rails ecosystems, largely on the back-end.

Husband, father, gamer, and all-around geek. Ask about my latest 3d print, or toy software project.