Documentation
¶
Overview ¶
Package circuitbreaker implements the Circuit-Breaker pattern.
The transformation of circuitbreaker's state is as follows:
- Assuming the number of requests reachs the threshold(Config.TriggerThreshold), initial state is CLOSE.
- After 1, if the error rate or the rate of high latency exceeds the threshold(Config.ErrorRate/HighLatencyRate), the circuitbreaker is OPEN.
- Otherwise for 2, the circuitbreaker will be CLOSE.
- After 2, the circuitbreaker remains OPEN until some amount of time(Config.SleepWindow) pass, then it's the HALF-OPEN which let a single request through, if the request fails, it returns to the OPEN. If the request succeeds, the circuitbreaker is CLOSE, and 1 takes over again.
Example ¶
cb := New(DefaultConfig())
func() (err error) {
c := cb.Circuit() // DO NOT reuse it, create a new one each time.
if c.IsInterrupted() {
err = ErrIsOpen
return // System is not healthy, return immediately.
}
defer func() { c.Trace(err != nil) }()
// err = doSth()
fmt.Println(err)
return
}()
func() { // Use Run for "convenience".
err := cb.Run(func() error {
time.Sleep(time.Millisecond)
return fmt.Errorf("is ok")
})
fmt.Println(err)
}()
Output: <nil> is ok
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ErrIsOpen = errors.New("circuitbreaker is open: not healthy")
ErrIsOpen means circuitbreaker is open, the system or API is not healthy.
Functions ¶
This section is empty.
Types ¶
type Circuit ¶
type Circuit struct {
// contains filtered or unexported fields
}
Circuit is used for every call.
func (Circuit) IsInterrupted ¶
IsInterrupted returns true if the circuit is interrupted, the caller should return immediately. Otherwise, returns false.
type CircuitBreaker ¶
type CircuitBreaker struct {
// contains filtered or unexported fields
}
CircuitBreaker traces the failures then protects the system.
There is a lock inside, in case of you worry about the performance, use multiple CircuitBreaker for defferent kinds of API(request type),
func New ¶
func New(conf Config) *CircuitBreaker
New creates a new CircuitBreaker. It doesn't check the Config for the caller.
func (*CircuitBreaker) Circuit ¶
func (cb *CircuitBreaker) Circuit() Circuit
Circuit creates a Circuit, each request(API call) requires exactly one Circuit, DO NOT reuse it or ignore it. You can use Run for "convenience".
func (*CircuitBreaker) Run ¶
func (cb *CircuitBreaker) Run(fn func() error) (err error)
Run is a shortcut for the workflow.
type Config ¶
type Config struct {
// TriggerThreshold is the threshold of total requests to trigger the circuitbreaker,
// 0 means never trigger.
TriggerThreshold int
// CountWindow is the time window to keep stats, any stats before the window will be droped.
CountWindow time.Duration
// SleepWindow is the wait time before recovering.
SleepWindow time.Duration
// ErrorRate is the error rate to trigger the circuitbreaker.
ErrorRate float64
// HighLatencyValue is the max acceptable latency.
HighLatencyValue time.Duration
// HighLatencyRate is the rate for HighLatencyValue to trigger the circuitbreaker.
HighLatencyRate float64
// CoverPanic will recover the panic, only used in Run.
CoverPanic bool
}
Config configures the CircuitBreaker.
func DefaultConfig ¶
func DefaultConfig() Config
DefaultConfig creates a default Config, it is just an example.
Source Files