gobreaker implements the Circuit Breaker pattern in Go.
go get github.com/sony/gobreaker
The struct CircuitBreaker is a state machine to prevent sending requests that are likely to fail. The function NewCircuitBreaker creates a new CircuitBreaker.
func NewCircuitBreaker(st Settings) *CircuitBreakerYou can configure CircuitBreaker by the struct Settings:
type Settings struct {
Name string
MaxRequests uint32
Interval time.Duration
Timeout time.Duration
ReadyToTrip func(counts Counts) bool
OnStateChange func(name string, from State, to State)
}-
Name is the name of the CircuitBreaker.
-
MaxRequests is the maximum number of requests allowed to pass through when the CircuitBreaker is half-open. If MaxRequests is 0, the CircuitBreaker allows only 1 request.
-
Interval is the cyclic period of the closed state for the CircuitBreaker to clear the internal Counts, described later in this section. If Interval is 0, the CircuitBreaker doesn't clear the internal Counts during the closed state.
-
Timeout is the period of the open state, after which the state of the CircuitBreaker becomes half-open. If Timeout is 0, the timeout value of the CircuitBreaker is set to 60 seconds.
-
ReadyToTrip is called with a copy of Counts whenever a request fails in the closed state. If ReadyToTrip returns true, the CircuitBreaker will be placed into the open state. If ReadyToTrip is nil, default ReadyToTrip is used. Default ReadyToTrip returns true when the number of consecutive failures is more than 5.
-
OnStateChange is called whenever the state of the CircuitBreaker changes.
The struct Counts holds the numbers of requests and their successes/failures:
type Counts struct {
Requests uint32
TotalSuccesses uint32
TotalFailures uint32
ConsecutiveSuccesses uint32
ConsecutiveFailures uint32
}CircuitBreaker clears the internal Counts either on the change of the state or at the closed-state intervals. Counts ignores the results of the requests sent before clearing.
CircuitBreaker can wrap any function to send a request:
func (cb *CircuitBreaker) Execute(req func() (interface{}, error)) (interface{}, error)The method Execute runs the given request if the CircuitBreaker accepts it. Execute returns an error instantly if the CircuitBreaker rejects the request. Otherwise, Execute returns the result of the request. If a panic occurs in the request, the CircuitBreaker handles it as an error and causes the same panic again.
var cb *breaker.CircuitBreaker
func Get(url string) ([]byte, error) {
body, err := cb.Execute(func() (interface{}, error) {
resp, err := http.Get(url)
if err != nil {
return nil, err
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
return body, nil
})
if err != nil {
return nil, err
}
return body.([]byte), nil
}See example for details.
The MIT License (MIT)
See LICENSE for details.