熔斷降級 · PHP/Python/前端/Linux 等等學習筆記

[TOC] ### 熔斷降級熔斷器有三種狀態： 1. Closed 狀態：也是初始狀態，該狀態下，熔斷器會保持閉合，對資源的訪問直接通過熔斷器的檢查。 2. Open 狀態：斷開狀態，熔斷器處于開啟狀態，對資源的訪問會被切斷。 3. Half-Open 狀態：半開狀態，該狀態下除了探測流量，其余對資源的訪問也會被切斷。探測流量指熔斷器處于半開狀態時，會周期性的允許一定數目的探測請求通過，如果探測請求能夠正常的返回，代表探測成功，此時熔斷器會重置狀態到 Closed 狀態，結束熔斷；如果探測失敗，則回滾到 Open 狀態。這三種狀態之間的轉換關系這里做一個更加清晰的解釋： 1. 初始狀態下，熔斷器處于 Closed 狀態。如果基于熔斷器的統計數據表明當前資源觸發了設定的閾值，那么熔斷器會切換狀態到 Open 狀態； 2. Open 狀態即代表熔斷狀態，所有請求都會直接被拒絕。熔斷器規則中會配置一個熔斷超時重試的時間，經過熔斷超時重試時長后熔斷器會將狀態置為 Half-Open 狀態，從而進行探測機制； 3. 處于 Half-Open 狀態的熔斷器會周期性去做探測。三種熔斷策略規則配置 ``` // 慢調用比例規則 rule1 := &Rule{ Resource: "abc", Strategy: SlowRequestRatio, RetryTimeoutMs: 5000, MinRequestAmount: 10, StatIntervalMs: 10000, MaxAllowedRtMs: 20, Threshold: 0.1, }, // 錯誤比例規則 rule1 := &Rule{ Resource: "abc", Strategy: ErrorRatio, RetryTimeoutMs: 5000, MinRequestAmount: 10, StatIntervalMs: 10000, Threshold: 0.1, }, // 錯誤計數規則 rule1 := &Rule{ Resource: "abc", Strategy: ErrorCount, RetryTimeoutMs: 5000, MinRequestAmount: 10, StatIntervalMs: 10000, Threshold: 100, }, ``` <details> <summary>main.go</summary> ``` package main import ( "fmt" "log" "math/rand" "time" sentinel "github.com/alibaba/sentinel-golang/api" "github.com/alibaba/sentinel-golang/core/circuitbreaker" "github.com/alibaba/sentinel-golang/util" ) type stateChangeTestListener struct { } func (s *stateChangeTestListener) OnTransformToClosed(prev circuitbreaker.State, rule circuitbreaker.Rule) { fmt.Printf("rule.steategy: %+v, From %s to Closed, time: %d\n", rule.Strategy, prev.String(), util.CurrentTimeMillis()) } func (s *stateChangeTestListener) OnTransformToOpen(prev circuitbreaker.State, rule circuitbreaker.Rule, snapshot interface{}) { fmt.Printf("rule.steategy: %+v, From %s to Open, snapshot: %.2f, time: %d\n", rule.Strategy, prev.String(), snapshot, util.CurrentTimeMillis()) } func (s *stateChangeTestListener) OnTransformToHalfOpen(prev circuitbreaker.State, rule circuitbreaker.Rule) { fmt.Printf("rule.steategy: %+v, From %s to Half-Open, time: %d\n", rule.Strategy, prev.String(), util.CurrentTimeMillis()) } func main() { err := sentinel.InitDefault() if err != nil { log.Fatal(err) } ch := make(chan struct{}) // Register a state change listener so that we could observer the state change of the internal circuit breaker. circuitbreaker.RegisterStateChangeListeners(&stateChangeTestListener{}) _, err = circuitbreaker.LoadRules([]*circuitbreaker.Rule{ // Statistic time span=10s, recoveryTimeout=3s, slowRtUpperBound=50ms, maxSlowRequestRatio=50% { Resource: "abc", Strategy: circuitbreaker.SlowRequestRatio, RetryTimeoutMs: 3000, MinRequestAmount: 10, StatIntervalMs: 10000, // 在 10s 的統計時間 MaxAllowedRtMs: 50, // 大于此時間的將視為錯誤鏈接 Threshold: 0.5, // 大于 MaxAllowedRtMs 比例大于50 }, // Statistic time span=10s, recoveryTimeout=3s, maxErrorRatio=50% //{ // Resource: "abc", // Strategy: circuitbreaker.ErrorRatio, //熔斷策略:錯誤比例規則 // RetryTimeoutMs: 3000, //重試時間 // MinRequestAmount: 10, // 若當前統計周期內的請求數小于此值，即使達到熔斷條件規則也不會觸發 // StatIntervalMs: 10000, // 統計的時間窗口長度 // Threshold: 0.5,// 50% 也就是如果當前資源的慢調用比例如果高于Threshold，那么熔斷器就會斷開；否則保持閉合狀態 //}, }) if err != nil { log.Fatal(err) } //go func() { // for { // e, b := sentinel.Entry("abc") // if b != nil { // //fmt.Println("g1blocked") // duration := time.Duration(rand.Uint64()%20) * time.Millisecond // fmt.Printf("g1blocked %v \n",duration) // time.Sleep(duration) // } else { // if rand.Uint64()%20 > 9 { // // Record current invocation as error. // sentinel.TraceError(e, errors.New("biz error")) // } // //fmt.Println("g1passed") // duration := time.Duration(rand.Uint64()%80+10) * time.Millisecond // fmt.Printf("g1passed %v\n",duration) // time.Sleep(duration) // e.Exit() // } // } //}() go func() { for { e, b := sentinel.Entry("abc") if b != nil { //fmt.Println("g2blocked") duration := time.Duration(rand.Uint64()%20) * time.Millisecond fmt.Printf("g2blocked %v \n",duration) time.Sleep(duration) } else { //fmt.Println("g2passed") duration := time.Duration(rand.Uint64()%80) * time.Millisecond fmt.Printf("g2passed %v\n",duration) time.Sleep(duration) e.Exit() } } }() <-ch } ``` </details> <br/>