cbreaker

Documentation

Overview

Package cbreaker implements circuit breaker similar to https://github.com/Netflix/Hystrix/wiki/How-it-Works

Vulcan circuit breaker watches the error condtion to match after which it activates the fallback scenario, e.g. returns the response code or redirects the request to another location

Circuit breakers start in the Standby state first, observing responses and watching location metrics.

Once the Circuit breaker condition is met, it enters the "Tripped" state, where it activates fallback scenario for all requests during the FallbackDuration time period and reset the stats for the location.

After FallbackDuration time period passes, Circuit breaker enters "Recovering" state, during that state it will start passing some traffic back to the endpoints, increasing the amount of passed requests using linear function:

allowedRequestsRatio = 0.5 * (Now() - StartRecovery())/RecoveryDuration

Two scenarios are possible in the "Recovering" state: 1. Condition matches again, this will reset the state to "Tripped" and reset the timer. 2. Condition does not match, circuit breaker enters "Standby" state

It is possible to define actions (e.g. webhooks) of transitions between states:

* OnTripped action is called on transition (Standby -> Tripped) * OnStandby action is called on transition (Recovering -> Standby)

Index

• type CircuitBreaker
  • func New(next http.Handler, expression string, options ...CircuitBreakerOption) (*CircuitBreaker, error)
  • func (c *CircuitBreaker) ServeHTTP(w http.ResponseWriter, req *http.Request)
  • func (c *CircuitBreaker) String() string
  • func (c *CircuitBreaker) Wrap(next http.Handler)
• type CircuitBreakerOption
  • func CheckPeriod(d time.Duration) CircuitBreakerOption
  • func Clock(clock timetools.TimeProvider) CircuitBreakerOption
  • func Fallback(h http.Handler) CircuitBreakerOption
  • func FallbackDuration(d time.Duration) CircuitBreakerOption
  • func Logger(l *log.Logger) CircuitBreakerOption
  • func OnStandby(s SideEffect) CircuitBreakerOption
  • func OnTripped(s SideEffect) CircuitBreakerOption
  • func RecoveryDuration(d time.Duration) CircuitBreakerOption
• type Redirect
• type RedirectFallback
  • func NewRedirectFallback(r Redirect) (*RedirectFallback, error)
  • func NewRedirectFallbackWithLogger(r Redirect, l *log.Logger) (*RedirectFallback, error)
  • func (f *RedirectFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)
• type Response
• type ResponseFallback
  • func NewResponseFallback(r Response) (*ResponseFallback, error)
  • func NewResponseFallbackWithLogger(r Response, l *log.Logger) (*ResponseFallback, error)
  • func (f *ResponseFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)
• type SideEffect
• type Webhook
• type WebhookSideEffect
  • func NewWebhookSideEffect(w Webhook) (*WebhookSideEffect, error)
  • func NewWebhookSideEffectsWithLogger(w Webhook, l *log.Logger) (*WebhookSideEffect, error)
  • func (w *WebhookSideEffect) Exec() error

Types

type CircuitBreaker

type CircuitBreaker struct {
	// contains filtered or unexported fields
}

CircuitBreaker is http.Handler that implements circuit breaker pattern

func New

func New(next http.Handler, expression string, options ...CircuitBreakerOption) (*CircuitBreaker, error)

New creates a new CircuitBreaker middleware

func (*CircuitBreaker) ServeHTTP

func (c *CircuitBreaker) ServeHTTP(w http.ResponseWriter, req *http.Request)

func (*CircuitBreaker) String

func (c *CircuitBreaker) String() string

String returns log-friendly representation of the circuit breaker state

func (*CircuitBreaker) Wrap

func (c *CircuitBreaker) Wrap(next http.Handler)

Wrap sets the next handler to be called by circuit breaker handler.

type CircuitBreakerOption

type CircuitBreakerOption func(*CircuitBreaker) error

CircuitBreakerOption represents an option you can pass to New. See the documentation for the individual options below.

func CheckPeriod

func CheckPeriod(d time.Duration) CircuitBreakerOption

CheckPeriod is how long the CircuitBreaker will wait between successive checks of the breaker condition.

func Clock

func Clock(clock timetools.TimeProvider) CircuitBreakerOption

Clock allows you to fake che CircuitBreaker's view of the current time. Intended for unit tests.

func Fallback

func Fallback(h http.Handler) CircuitBreakerOption

Fallback defines the http.Handler that the CircuitBreaker should route requests to when it prevents a request from taking its normal path.

func FallbackDuration

func FallbackDuration(d time.Duration) CircuitBreakerOption

FallbackDuration is how long the CircuitBreaker will remain in the Tripped state before trying to recover.

func Logger

func Logger(l *log.Logger) CircuitBreakerOption

Logger defines the logger the circuit breaker will use.

It defaults to logrus.StandardLogger(), the global logger used by logrus.

func OnStandby

func OnStandby(s SideEffect) CircuitBreakerOption

OnStandby sets a SideEffect to run when entering the Standby state. Only one SideEffect can be set for this hook.

func OnTripped

func OnTripped(s SideEffect) CircuitBreakerOption

OnTripped sets a SideEffect to run when entering the Tripped state. Only one SideEffect can be set for this hook.

func RecoveryDuration

func RecoveryDuration(d time.Duration) CircuitBreakerOption

RecoveryDuration is how long the CircuitBreaker will take to ramp up requests during the Recovering state.

type Redirect

type Redirect struct {
	URL          string
	PreservePath bool
}

Redirect redirect model

type RedirectFallback

type RedirectFallback struct {
	// contains filtered or unexported fields
}

RedirectFallback fallback redirect handler

func NewRedirectFallback

func NewRedirectFallback(r Redirect) (*RedirectFallback, error)

NewRedirectFallback creates a new RedirectFallback

func NewRedirectFallbackWithLogger

func NewRedirectFallbackWithLogger(r Redirect, l *log.Logger) (*RedirectFallback, error)

NewRedirectFallbackWithLogger creates a new RedirectFallback

func (*RedirectFallback) ServeHTTP

func (f *RedirectFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)

type Response

type Response struct {
	StatusCode  int
	ContentType string
	Body        []byte
}

Response response model

type ResponseFallback

type ResponseFallback struct {
	// contains filtered or unexported fields
}

ResponseFallback fallback response handler

func NewResponseFallback

func NewResponseFallback(r Response) (*ResponseFallback, error)

NewResponseFallback creates a new ResponseFallback

func NewResponseFallbackWithLogger

func NewResponseFallbackWithLogger(r Response, l *log.Logger) (*ResponseFallback, error)

NewResponseFallbackWithLogger creates a new ResponseFallback

func (*ResponseFallback) ServeHTTP

func (f *ResponseFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)

type SideEffect

type SideEffect interface {
	Exec() error
}

SideEffect a side effect

type Webhook

type Webhook struct {
	URL     string
	Method  string
	Headers http.Header
	Form    url.Values
	Body    []byte
}

Webhook Web hook

type WebhookSideEffect

type WebhookSideEffect struct {
	// contains filtered or unexported fields
}

WebhookSideEffect a web hook side effect

func NewWebhookSideEffect

func NewWebhookSideEffect(w Webhook) (*WebhookSideEffect, error)

NewWebhookSideEffect creates a new WebhookSideEffect

func NewWebhookSideEffectsWithLogger

func NewWebhookSideEffectsWithLogger(w Webhook, l *log.Logger) (*WebhookSideEffect, error)

NewWebhookSideEffectsWithLogger creates a new WebhookSideEffect

func (*WebhookSideEffect) Exec

func (w *WebhookSideEffect) Exec() error

Exec execute the side effect