【go-micro實踐】hystrix熔斷及dashboard展現

github完整代碼地址 我的博客

hystrix-go

hystrix是Netflix開源的一個JAVA項目，不過GitHub也有golang的實現版本hystrix-go

hystrix-dashboard

hystrix並無自帶一個儀表盤，沒法直觀的查看接口的健康情況。因此，咱們採用GitHub的一個開源實現hystrix-dashboard。

docker run --name hystrix-dashboard -d -p 8081:9002 mlabouardy/hystrix-dashboard:latest
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micro API網關插件

關於hystrix的工做原理，能夠查閱相關資料，這裏只講解如何封裝插件在micro API網關中使用。

err := hystrix.Do("my_command", func() error {
	// talk to other services
	return nil
}, nil)
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使用hystrix.Do() 同步API，第一個參數是command, 應該是與當前請求一一對應的一個名稱，如入「GET-/test」。第二個參數傳入一個函數，函數包含我咱們本身的錯誤邏輯，當請求失敗時應該返回error。hystrix會根據咱們的失敗率執行熔斷策略。

封裝Handler

// BreakerWrapper hystrix breaker
func BreakerWrapper(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		name := r.Method + "-" + r.RequestURI
		log.Println(name)
		err := hystrix.Do(name, func() error {
			sct := &status_code.StatusCodeTracker{ResponseWriter: w, Status: http.StatusOK}
			h.ServeHTTP(sct.WrappedResponseWriter(), r)

			if sct.Status >= http.StatusBadRequest {
				str := fmt.Sprintf("status code %d", sct.Status)
				log.Println(str)
				return errors.New(str)
			}
			return nil
		}, nil)
		if err != nil {
			log.Println("hystrix breaker err: ", err)
			return
		}
	})
}
...
// 註冊插件
plugin.Register(plugin.NewPlugin(
		plugin.WithName("breaker"),
		plugin.WithHandler(
			hystrix.BreakerWrapper,
		),
	))
...
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在 hystrix.Do 中，首先執行 h.ServeHTTP，該函數返回後，即請求執行完成。咱們判斷HTTP狀態碼，若是大於StatusBadRequest，則認爲此次請求失敗，返回一個錯誤，hystrix會收集錯誤，若是錯誤率達到某個閥值，就會觸發斷路器。 在作實驗時，能夠直接在main函數裏設置hystrix的幾個默認配置參數，方便看效果

// hystrix-go/hystrix/settings.go

	// DefaultTimeout is how long to wait for command to complete, in milliseconds
	DefaultTimeout = 1000
	// DefaultMaxConcurrent is how many commands of the same type can run at the same time
	DefaultMaxConcurrent = 10
	// DefaultVolumeThreshold is the minimum number of requests needed before a circuit can be tripped due to health
	DefaultVolumeThreshold = 20
	// DefaultSleepWindow is how long, in milliseconds, to wait after a circuit opens before testing for recovery
	DefaultSleepWindow = 5000
	// DefaultErrorPercentThreshold causes circuits to open once the rolling measure of errors exceeds this percent of requests
	DefaultErrorPercentThreshold = 50

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hystrix-go庫還提供爲每一個commond動態設置配置的接口，咱們能夠經過這個接口結合配置中心，動態調節服務。

hystrix.ConfigureCommand("my_command", hystrix.CommandConfig{
	Timeout:               1000,
	MaxConcurrentRequests: 100,
	ErrorPercentThreshold: 25,
})
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接入hystrix-dashboard

docker run --name hystrix-dashboard -d -p 8081:9002 mlabouardy/hystrix-dashboard:latest
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打開 http://localhost:8081/hystrix , 輸入 http://{ip}:81/hystrix.stream , 此處ip爲本機ip，由於hystrix-dashboard是容器啓動的，沒法直接訪問本機127.0.0.1。

Enable dashboard metrics In your main.go, register the event stream HTTP handler on a port and launch it in a goroutine. Once you configure turbine for your Hystrix Dashboard to start streaming events, your commands will automatically begin appearing.

hystrixStreamHandler := hystrix.NewStreamHandler()
hystrixStreamHandler.Start()
go http.ListenAndServe(net.JoinHostPort("", "81"), hystrixStreamHandler)
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