1. Circuit Breaker Pattern

Similar to electrical fuses that prevent fires when a circuit that is connected to the electrical grid starts drawing a high amount of power which causes the wires to heat up and combust, the circuit breaker design pattern is a fail-first mechanism that shuts down the circuit, request/response relationship or a service in the case of software development, to prevent bigger failures.

Note: The words "circuit" and "service" are used synonymously throught this document.

1.1. Implementation

Below is the implementation of a very simple circuit breaker to illustrate the purpose of the circuit breaker design pattern.

1.1.1. Operation Counter

circuit.Counter is a simple counter that records success and failure states of a circuit along with a timestamp and calculates the consecutive number of failures.

package circuit

import (

type State int

const (
    UnknownState State = iota

type Counter interface {
    ConsecutiveFailures() uint32
    LastActivity() time.Time

1.1.2. Circuit Breaker

Circuit is wrapped using the circuit.Breaker closure that keeps an internal operation counter. It returns a fast error if the circuit has failed consecutively more than the specified threshold. After a while it retries the request and records it.

Note: Context type is used here to carry deadlines, cancelation signals, and other request-scoped values across API boundaries and between processes.

package circuit

import (

type Circuit func(context.Context) error

func Breaker(c Circuit, failureThreshold uint32) Circuit {
    cnt := NewCounter()

    return func(ctx context) error {
        if cnt.ConsecutiveFailures() >= failureThreshold {
            canRetry := func(cnt Counter) {
                backoffLevel := Cnt.ConsecutiveFailures() - failureThreshold

                // Calculates when should the circuit breaker resume propagating requests
                // to the service
                shouldRetryAt := cnt.LastActivity().Add(time.Seconds * 2 << backoffLevel)

                return time.Now().After(shouldRetryAt)

            if !canRetry(cnt) {
                // Fails fast instead of propagating requests to the circuit since
                // not enough time has passed since the last failure to retry
                return ErrServiceUnavailable

        // Unless the failure threshold is exceeded the wrapped service mimics the
        // old behavior and the difference in behavior is seen after consecutive failures
        if err := c(ctx); err != nil {
            return err

        return nil
  • sony/gobreaker is a well-tested and intuitive circuit breaker implementation for real-world use cases.
Copyright © studygolang.com 2013 all right reserved,powered by Gitbook该文件修订时间: 2017-07-21 20:12:31

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