壹、入圍方案Sentinel github地址：https://sentinelguard.io/zh-cn/docs/introduction.html 阿里出品，Spring Cloud Alibaba限流組件，目前持續更新中 自帶Dashboard，可以查看接口Qps等，并且可以動態修改各種規則 流量控制，直接限流、冷啟動、排隊 熔斷降級，限制并發限制數和相應時間 系統負載保護，提供系統級別防護，限制總體CPU等 主要核心：資源，規則（流量控制規則、熔斷降級規則、系統保護規則、來源訪問控制規則 和 熱點參數規則。），和指標 文檔非常清晰和詳細，中文 支持動態規則（推模式和拉模式） Hystrix github地址：https://github.com/Netflix/Hystrix/wiki Netflix出品，Spring Cloud Netflix限流組件，已經停止新特性開發，只進行bug修復，最近更新為2018年，功能穩定 有簡單的dashboard頁面 以隔離和熔斷為主的容錯機制，超時或被熔斷的調用將會快速失敗，并可以提供 fallback 機制的初代熔斷框架，異常統計基于滑動窗口 resilience4j github地址：https://resilience4j.readme.io/docs 是一款輕量、簡單，并且文檔非常清晰、豐富的熔斷工具。是Hystrix替代品，實現思路和Hystrix一致，目前持續更新中 需要自己對micrometer、prometheus以及Dropwizard metrics進行整合 CircuitBreaker 熔斷 Bulkhead 隔離 RateLimiter QPS限制 Retry 重試 TimeLimiter 超時限制 Cache 緩存 自己實現(基于Guava) 基于Guava的令牌桶，可以輕松實現對QPS進行限流 貳、技術對比

叁、應用改造3.1、sentinel

3.1.1、引入依賴

<dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId> <version>2.0.3.RELEASE</version></dependency>

3.1.2、改造接口或者service層

@SentinelResource(value = 'allInfos',fallback = 'errorReturn')

@Target({ElementType.METHOD, ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Inheritedpublic @interface SentinelResource { //資源名稱 String value() default ''; //流量方向 EntryType entryType() default EntryType.OUT; //資源類型 int resourceType() default 0; //異常處理方法 String blockHandler() default ''; //異常處理類 Class<?>[] blockHandlerClass() default {}; //熔斷方法 String fallback() default ''; //默認熔斷方法 String defaultFallback() default ''; //熔斷類 Class<?>[] fallbackClass() default {}; //統計異常 Class<? extends Throwable>[] exceptionsToTrace() default {Throwable.class}; //忽略異常 Class<? extends Throwable>[] exceptionsToIgnore() default {};}

@RequestMapping('/get')@ResponseBody@SentinelResource(value = 'allInfos',fallback = 'errorReturn')public JsonResult allInfos(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num){ try { if (num % 2 == 0) {log.info('num % 2 == 0');throw new BaseException('something bad with 2', 400); } return JsonResult.ok(); } catch (ProgramException e) { log.info('error'); return JsonResult.error('error'); } }

3.1.3、針對接口配置熔斷方法或者限流方法

默認過濾攔截所有Controller接口

/** * 限流，參數需要和方法保持一致 * @param request * @param response * @param num * @return * @throws BlockException */ public JsonResult errorReturn(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num) throws BlockException { return JsonResult.error('error 限流' + num ); } /** * 熔斷，參數需要和方法保持一直，并且需要添加BlockException異常 * @param request * @param response * @param num * @param b * @return * @throws BlockException */ public JsonResult errorReturn(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num,BlockException b) throws BlockException { return JsonResult.error('error 熔斷' + num ); }

注意也可以不配置限流或者熔斷方法。通過全局異常去捕獲UndeclaredThrowableException或者BlockException避免大量的開發量

3.1.4、接入dashboard

spring: cloud: sentinel: transport: port: 8719 dashboard: localhost:8080

3.1.5、規則持久化和動態更新

接入配置中心如：zookeeper等等，并對規則采用推模式

3.2、hystrix

3.2.1、引入依賴

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId></dependency><dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId> <version>2.0.4.RELEASE</version></dependency><dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-hystrix</artifactId> <version>2.0.4.RELEASE</version></dependency>

3.2.2、改造接口

@HystrixCommand(fallbackMethod = 'timeOutError')

@Target({ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)@Inherited@Documentedpublic @interface HystrixCommand { String groupKey() default ''; String commandKey() default ''; String threadPoolKey() default ''; String fallbackMethod() default ''; HystrixProperty[] commandProperties() default {}; HystrixProperty[] threadPoolProperties() default {}; Class<? extends Throwable>[] ignoreExceptions() default {}; ObservableExecutionMode observableExecutionMode() default ObservableExecutionMode.EAGER; HystrixException[] raiseHystrixExceptions() default {}; String defaultFallback() default '';}

@RequestMapping('/get')@ResponseBody@HystrixCommand(fallbackMethod = 'fallbackMethod')public JsonResult allInfos(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num){ try { if (num % 3 == 0) { log.info('num % 3 == 0'); throw new BaseException('something bad whitch 3', 400); } return JsonResult.ok(); } catch (ProgramException | InterruptedException exception) { log.info('error'); return JsonResult.error('error'); }}

3.2.3、針對接口配置熔斷方法

/** * 該方法是熔斷回調方法，參數需要和接口保持一致 * @param request * @param response * @param num * @return */public JsonResult fallbackMethod(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num) { response.setStatus(500); log.info('發生了熔斷??！'); return JsonResult.error('熔斷');}

3.2.4、配置默認策略

hystrix: command: default: execution: isolation: strategy: THREAD thread: # 線程超時15秒,調用Fallback方法 timeoutInMilliseconds: 15000 metrics: rollingStats: timeInMilliseconds: 15000 circuitBreaker: # 10秒內出現3個以上請求(已臨近閥值),并且出錯率在50%以上,開啟斷路器.斷開服務,調用Fallback方法 requestVolumeThreshold: 3 sleepWindowInMilliseconds: 10000

3.2.5、接入監控

曲線：用來記錄2分鐘內流量的相對變化，我們可以通過它來觀察到流量的上升和下降趨勢。

集群監控需要用到注冊中心

3.3、resilience4j

3.3.1、引入依賴

dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope></dependency> <dependency> <groupId>io.github.resilience4j</groupId> <artifactId>resilience4j-spring-boot2</artifactId> <version>1.6.1</version></dependency> <dependency> <groupId>io.github.resilience4j</groupId> <artifactId>resilience4j-bulkhead</artifactId> <version>1.6.1</version></dependency> <dependency> <groupId>io.github.resilience4j</groupId> <artifactId>resilience4j-ratelimiter</artifactId> <version>1.6.1</version></dependency> <dependency> <groupId>io.github.resilience4j</groupId> <artifactId>resilience4j-timelimiter</artifactId> <version>1.6.1</version></dependency>

可以按需要引入：bulkhead，ratelimiter，timelimiter等

3.3.2、改造接口

@RequestMapping('/get')@ResponseBody//@TimeLimiter(name = 'BulkheadA',fallbackMethod = 'fallbackMethod')@CircuitBreaker(name = 'BulkheadA',fallbackMethod = 'fallbackMethod')@Bulkhead(name = 'BulkheadA',fallbackMethod = 'fallbackMethod')public JsonResult allInfos(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num){ log.info('param----->' + num); try { //Thread.sleep(num); if (num % 2 == 0) { log.info('num % 2 == 0'); throw new BaseException('something bad with 2', 400); } if (num % 3 == 0) { log.info('num % 3 == 0'); throw new BaseException('something bad whitch 3', 400); } if (num % 5 == 0) { log.info('num % 5 == 0'); throw new ProgramException('something bad whitch 5', 400); } if (num % 7 == 0) { log.info('num % 7 == 0'); int res = 1 / 0; } return JsonResult.ok(); } catch (BufferUnderflowException e) { log.info('error'); return JsonResult.error('error'); }}

3.3.3、針對接口配置熔斷方法

/** * 需要參數一致，并且加上相應異常 * @param request * @param response * @param num * @param exception * @return */public JsonResult fallbackMethod(HttpServletRequest request, HttpServletResponse response, @RequestParam Integer num, BulkheadFullException exception) { return JsonResult.error('error 熔斷' + num );}

3.3.4、配置規則

resilience4j.circuitbreaker: instances: backendA: registerHealthIndicator: true slidingWindowSize: 100 backendB: registerHealthIndicator: true slidingWindowSize: 10 permittedNumberOfCallsInHalfOpenState: 3 slidingWindowType: TIME_BASED minimumNumberOfCalls: 20 waitDurationInOpenState: 50s failureRateThreshold: 50 eventConsumerBufferSize: 10 recordFailurePredicate: io.github.robwin.exception.RecordFailurePredicate resilience4j.retry: instances: backendA: maxRetryAttempts: 3 waitDuration: 10s enableExponentialBackoff: true exponentialBackoffMultiplier: 2 retryExceptions:- org.springframework.web.client.HttpServerErrorException- java.io.IOException ignoreExceptions:- io.github.robwin.exception.BusinessException backendB: maxRetryAttempts: 3 waitDuration: 10s retryExceptions:- org.springframework.web.client.HttpServerErrorException- java.io.IOException ignoreExceptions:- io.github.robwin.exception.BusinessException resilience4j.bulkhead: instances: backendA: maxConcurrentCalls: 10 backendB: maxWaitDuration: 10ms maxConcurrentCalls: 20 resilience4j.thread-pool-bulkhead: instances: backendC: maxThreadPoolSize: 1 coreThreadPoolSize: 1 queueCapacity: 1 resilience4j.ratelimiter: instances: backendA: limitForPeriod: 10 limitRefreshPeriod: 1s timeoutDuration: 0 registerHealthIndicator: true eventConsumerBufferSize: 100 backendB: limitForPeriod: 6 limitRefreshPeriod: 500ms timeoutDuration: 3s resilience4j.timelimiter: instances: backendA: timeoutDuration: 2s cancelRunningFuture: true backendB: timeoutDuration: 1s cancelRunningFuture: false

配置的規則可以被代碼覆蓋

3.3.5、配置監控

如grafana等

肆、關注點 是否需要過濾部分異常 是否需要全局默認規則 可能需要引入其他中間件 k8s流量控制 規則存儲和動態修改 接入改造代價 【后面的話】

個人建議的話，比較推薦sentinel，它提供了很多接口便于開發者自己拓展，同時我覺得他的規則動態更新也比較方便。最后是相關示例代碼:單體應用示例代碼

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