fastbreaker

fastbreaker implements the Circuit Breaker pattern in Go.

Installation

go get github.com/bluekiri/fastbreaker

Usage

The interface fastbreaker.FastBreaker is a state machine to prevent sending requests that are likely to fail. The function fastbreaker.New creates a new fastbreaker.FastBreaker.

func fastbreaker.New(configuration fastbreaker.Configuration) fastbreaker.FastBreaker

You can configure fastbreaker.FastBreaker by the struct fastbreaker.Configuration:

type Configuration struct {
    NumBuckets      int
    BucketDuration  time.Duration
    DurationOfBreak time.Duration
    ShouldTrip      ShouldTripFunc
}

• NumBuckets is the number of buckets of the rolling window. If NumBuckets is less than 1, the fastbreaker.DefaultNumBuckets is used.

• BucketDuration is the duration (truncated to the second) of every bucket. If BucketDuration is less than 1s, the fastbreaker.DefaultBucketDuration is used.

• DurationOfBreak is the time (truncated to the second) of the open state, after which the state becomes half-open. If DurationOfBreak is less than 1s, the fastbreaker.DefaultDurationOfBreak is used.

• ShouldTrip is called whenever a request fails in the closed state with the number of executions and the number of failures. If ShouldTrip returns true, fastbreaker.FastBreaker state becomes open. If ShouldTrip is nil, fastbreaker.DefaultShouldTrip is used. fastbreaker.DefaultShouldTrip returns true when the number of executions is greater than or equal to 10 and at least half the number of executions have failed.

Example

var cb fastbreaker.FastBreaker

func Get(url string) ([]byte, error) {
	feedback, err := cb.Allow()
	if err != nil {
		return nil, err
	}

	resp, err := http.Get(url)
	if err != nil {
		feedback(false)
		return nil, err
	}

	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		feedback(false)
		return nil, err
	}

	feedback(true)
	return body, nil
}

License

The MIT License (MIT)

See LICENSE for details.