gobreaker - ActiveState ActiveGo 1.8

Package gobreaker

import "github.com/sony/gobreaker"

Overview ▾

Package gobreaker implements the Circuit Breaker pattern. See https://msdn.microsoft.com/en-us/library/dn589784.aspx.

type CircuitBreaker

CircuitBreaker is a state machine to prevent sending requests that are likely to fail.

type CircuitBreaker struct {
    // contains filtered or unexported fields

func NewCircuitBreaker

func NewCircuitBreaker(st Settings) *CircuitBreaker

NewCircuitBreaker returns a new CircuitBreaker configured with the given Settings.

func (*CircuitBreaker) Execute

func (cb *CircuitBreaker) Execute(req func() (interface{}, error)) (interface{}, error)

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.

func (*CircuitBreaker) State

func (cb *CircuitBreaker) State() State

State returns the current state of the CircuitBreaker.

type Counts

Counts holds the numbers of requests and their successes/failures. 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.

type Counts struct {
    Requests             uint32
    TotalSuccesses       uint32
    TotalFailures        uint32
    ConsecutiveSuccesses uint32
    ConsecutiveFailures  uint32

type Settings

Settings configures CircuitBreaker:

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. If Interval is 0, the CircuitBreaker doesn't clear 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.

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)

type State

State is a type that represents a state of CircuitBreaker.

type State int

These constants are states of CircuitBreaker.

const (
    StateClosed State = iota

func (State) String

func (s State) String() string

String implements stringer interface.

type TwoStepCircuitBreaker

TwoStepCircuitBreaker is like CircuitBreaker but instead of surrounding a function with the breaker functionality, it only checks whether a request can proceed and expects the caller to report the outcome in a separate step using a callback.

type TwoStepCircuitBreaker struct {
    // contains filtered or unexported fields

func NewTwoStepCircuitBreaker

func NewTwoStepCircuitBreaker(st Settings) *TwoStepCircuitBreaker

NewTwoStepCircuitBreaker returns a new TwoStepCircuitBreaker configured with the given Settings.

func (*TwoStepCircuitBreaker) Allow

func (tscb *TwoStepCircuitBreaker) Allow() (done func(success bool), err error)

Allow checks if a new request can proceed. It returns a callback that should be used to register the success or failure in a separate step. If the Circuit Breaker doesn't allow requests it returns an error.

func (*TwoStepCircuitBreaker) State

func (tscb *TwoStepCircuitBreaker) State() State

State returns the current state of the TwoStepCircuitBreaker.


Name Synopsis