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 ...Option) (*CircuitBreaker, error)
  • func (c *CircuitBreaker) Fallback(f http.Handler)
  • func (c *CircuitBreaker) ServeHTTP(w http.ResponseWriter, req *http.Request)
  • func (c *CircuitBreaker) String() string
  • func (c *CircuitBreaker) Wrap(next http.Handler)
• type Option
  • func CheckPeriod(d time.Duration) Option
  • func Fallback(h http.Handler) Option
  • func FallbackDuration(d time.Duration) Option
  • func Logger(l utils.Logger) Option
  • func OnStandby(s SideEffect) Option
  • func OnTripped(s SideEffect) Option
  • func RecoveryDuration(d time.Duration) Option
  • func Verbose(verbose bool) Option
• type Redirect
• type RedirectFallback
  • func NewRedirectFallback(r Redirect, options ...RedirectFallbackOption) (*RedirectFallback, error)
  • func (f *RedirectFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)
• type RedirectFallbackOption
  • func RedirectFallbackDebug(debug bool) RedirectFallbackOption
  • func RedirectFallbackLogger(l utils.Logger) RedirectFallbackOption
• type Response
• type ResponseFallback
  • func NewResponseFallback(r Response, options ...ResponseFallbackOption) (*ResponseFallback, error)
  • func (f *ResponseFallback) ServeHTTP(w http.ResponseWriter, req *http.Request)
• type ResponseFallbackOption
  • func ResponseFallbackDebug(debug bool) ResponseFallbackOption
  • func ResponseFallbackLogger(l utils.Logger) ResponseFallbackOption
• type SideEffect
• type Webhook
• type WebhookSideEffect
  • func NewWebhookSideEffect(w Webhook) (*WebhookSideEffect, error)
  • func NewWebhookSideEffectsWithLogger(w Webhook, l utils.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 ...Option) (*CircuitBreaker, error)

New creates a new CircuitBreaker middleware.

func (*CircuitBreaker) Fallback

func (c *CircuitBreaker) Fallback(f http.Handler)

Fallback sets the fallback handler to be called by circuit breaker handler.

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 Option

type Option func(*CircuitBreaker) error

Option represents an option you can pass to New.

func CheckPeriod

func CheckPeriod(d time.Duration) Option

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

func Fallback

func Fallback(h http.Handler) Option

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) Option

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

func Logger

func Logger(l utils.Logger) Option

Logger defines the logger used by CircuitBreaker.

func OnStandby

func OnStandby(s SideEffect) Option

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) Option

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) Option

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

func Verbose

func Verbose(verbose bool) Option

Verbose additional debug information.

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, options ...RedirectFallbackOption) (*RedirectFallback, error)

NewRedirectFallback creates a new RedirectFallback.

func (*RedirectFallback) ServeHTTP

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

type RedirectFallbackOption

type RedirectFallbackOption func(*RedirectFallback) error

RedirectFallbackOption represents an option you can pass to NewRedirectFallback.

func RedirectFallbackDebug

func RedirectFallbackDebug(debug bool) RedirectFallbackOption

RedirectFallbackDebug additional debug information.

func RedirectFallbackLogger

func RedirectFallbackLogger(l utils.Logger) RedirectFallbackOption

RedirectFallbackLogger defines the logger used by ResponseFallback.

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, options ...ResponseFallbackOption) (*ResponseFallback, error)

NewResponseFallback creates a new ResponseFallback.

func (*ResponseFallback) ServeHTTP

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

type ResponseFallbackOption

type ResponseFallbackOption func(*ResponseFallback) error

ResponseFallbackOption represents an option you can pass to NewResponseFallback.

func ResponseFallbackDebug

func ResponseFallbackDebug(debug bool) ResponseFallbackOption

ResponseFallbackDebug additional debug information.

func ResponseFallbackLogger

func ResponseFallbackLogger(l utils.Logger) ResponseFallbackOption

ResponseFallbackLogger defines the logger used by ResponseFallback.

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 utils.Logger) (*WebhookSideEffect, error)

NewWebhookSideEffectsWithLogger creates a new WebhookSideEffect.

func (*WebhookSideEffect) Exec

func (w *WebhookSideEffect) Exec() error

Exec execute the side effect.