Breaker

Breaker is a middleware for Fox that rejects requests to a failing route, using the adaptive throttling described in the Google SRE book.

Disclaimer

The current API is not yet stabilized. Breaking changes may occur before v1.0.0 and will be noted on the release note.

Getting started

Installation

go get -u github.com/fox-toolkit/breaker

Feature

• One breaker per route, or one breaker shared by several routes.
• No lock on the request path and no allocation.
• Configurable failure ratio, window, cap and minimum number of requests.
• Configurable failure definition and rejection response.

Usage

package main

import (
	"errors"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"

	"github.com/fox-toolkit/breaker"
	"github.com/fox-toolkit/fox"
)

func main() {
	// One breaker per route.
	mw, err := breaker.Middleware()
	if err != nil {
		log.Fatalln(err)
	}

	// One breaker shared by every route it wraps.
	b, err := breaker.New(breaker.WithFailureRatio(0.3))
	if err != nil {
		log.Fatalln(err)
	}

	f := fox.MustRouter()

	api, _ := url.Parse("http://127.0.0.1:8081")
	apiProxy := fox.WrapH(httputil.NewSingleHostReverseProxy(api))
	f.MustAdd(fox.MethodAny, "/api/*{any}", apiProxy, fox.WithMiddleware(mw))

	orders, _ := url.Parse("http://127.0.0.1:8082")
	ordersProxy := fox.WrapH(httputil.NewSingleHostReverseProxy(orders))
	f.MustAdd(fox.MethodAny, "/orders", ordersProxy, fox.WithMiddleware(b.Middleware()))
	f.MustAdd(fox.MethodAny, "/orders/{id}", ordersProxy, fox.WithMiddleware(b.Middleware()))

	if err := http.ListenAndServe(":8080", f); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatalln(err)
	}
}

To apply the breaker to every route of the router, prefer registering it for route handlers.

mw, err := breaker.Middleware()
if err != nil {
	log.Fatalln(err)
}

// One breaker per route, for every route of the router.
f := fox.MustRouter(fox.WithMiddlewareFor(fox.RouteHandler, mw))