README
¶
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
}
-
NumBucketsis the number of buckets of the rolling window. IfNumBucketsis less than 1, thefastbreaker.DefaultNumBucketsis used. -
BucketDurationis the duration (truncated to the second) of every bucket. IfBucketDurationis less than 1s, thefastbreaker.DefaultBucketDurationis used. -
DurationOfBreakis the time (truncated to the second) of the open state, after which the state becomes half-open. IfDurationOfBreakis less than 1s, thefastbreaker.DefaultDurationOfBreakis used. -
ShouldTripis called whenever a request fails in the closed state with the number of executions and the number of failures. IfShouldTripreturns true,fastbreaker.FastBreakerstate becomes open. IfShouldTripisnil,fastbreaker.DefaultShouldTripis used.fastbreaker.DefaultShouldTripreturns 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.
Documentation
¶
Index ¶
Constants ¶
const ( // DefaultNumBuckets is the default number of buckets of a circuit breaker. Value = 10. DefaultNumBuckets = 10 // DefaultBucketDuration is the default duration of a bucket. Value = 1s. DefaultBucketDuration = 1 * time.Second // DefaultDurationOfBreak is the default duration of a circuit breaker break. Value = 5s DefaultDurationOfBreak = 5 * time.Second )
Variables ¶
var ErrCircuitOpen = errors.New("circuit breaker is open")
ErrCircuitOpen is the error returned by FastCircuitBreaker.Allow() when the circuit is open.
var ErrCircuitStopped = errors.New("circuit breaker is stopped")
ErrCircuitStopped is the error returned by FastCircuitBreaker.Allow() when the circuit is stopped.
Functions ¶
func DefaultShouldTrip ¶
DefaultShouldTrip is the default implementation of the ShouldTrip function. If will trip the circuit when there has been at least 20 executions and at least 50% of the executions failed.
Types ¶
type Configuration ¶
type Configuration struct {
NumBuckets int
BucketDuration time.Duration
DurationOfBreak time.Duration
ShouldTrip ShouldTripFunc
}
Configuration is a struct used to configure a circuit breaker.
type FastBreaker ¶
type FastBreaker interface {
// Configuration returns the actual configuration used to create the circuit breaker.
Configuration() Configuration
// Stop releases the circuit breaker resources.
Stop()
// Allow checks if the circuit breaker should allow the execution to proceed.
// Returns a function to report if the execution was successful when the execution is allowed or an
// error when it is not.
Allow() (func(bool), error)
// State returns the current State of the circuit breaker.
State() State
// Executions returns the number of executions the circuit breaker has allowed.
Executions() uint64
// Failures returns the number of executions reported as failed.
Failures() uint64
// Rejected returns the number of executions the circuit breaker has rejected.
Rejected() uint64
// RollingCounters returns the rolling executions and failures.
RollingCounters() (uint64, uint64)
}
FastBreaker is the interface implemented by the circuit breakers.
func New ¶
func New(configuration Configuration) FastBreaker
New creates a new CircuitBreaker with the passed Configuration.
type ShouldTripFunc ¶
A ShouldTripFunc tells the circuit breaker to trip when it returns true. If it returns false, the circuit breaker will remain closed.
type State ¶
type State uint32
State represents the state of a circuit breaker.
const ( // StateStopped is the circuit breaker state when it is stopped. StateStopped State = iota // StateClosed is the circuit breaker state when it is allowing executions. StateClosed // StateHalfOpen is the circuit breaker state when it tests if it should remain open // or reset to the closed state. StateHalfOpen // StateOpen is the circuit breaker state when it is rejecting executions. StateOpen )
Source Files
Directories