壹、入圍方案

Sentinel

• github地址：https://sentinelguard.io/zh-cn/docs/introduction.html
• 阿里出品，Spring Cloud Alibaba限流元件，目前持續更新中
• 自帶Dashboard，可以檢視介面Qps等，並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，限制併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 熱點引數規則。），和指標
• 文件非常清晰和詳細，中文
• 支援動態規則（推模式和拉模式）
  

Hystrix

• github地址：https://github.com/Netflix/Hystrix/wiki
• Netflix出品，Spring Cloud Netflix限流元件，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，超時或被熔斷的呼叫將會快速失敗，並可以提供 fallback 機制的初代熔斷框架，異常統計基於滑動視窗
  

resilience4j

• github地址：https://resilience4j.readme.io/docs
• 是一款輕量、簡單，並且文件非常清晰、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 快取
  

自己實現(基於Guava)

• 基於Guava的令牌桶，可以輕鬆實現對QPS進行限流
  

貳、技術對比

叄、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、改造介面或者service層

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

@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface SentinelResource {
  //資源名稱
  String value() default "";
 
  //流量方向
  EntryType entryType() default EntryType.OUT;
 
  //資源型別
  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 "";
 
  //預設熔斷方法
  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、針對介面配置熔斷方法或者限流方法

預設過濾攔截所有Controller介面

/**
   * 限流，引數需要和方法保持一致
   * @param request
   * @param response
   * @param num
   * @return
   * @throws BlockException
   */
  public JsonResult errorReturn(HttpServletRequest request,@RequestParam Integer num) throws BlockException {
    return JsonResult.error("error 限流" + num );
  }
 
  /**
   * 熔斷，引數需要和方法保持一直，並且需要新增BlockException異常
   * @param request
   * @param response
   * @param num
   * @param b
   * @return
   * @throws BlockException
   */
  public JsonResult errorReturn(HttpServletRequest request,@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。通過全域性異常去捕獲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，並對規則採用推模式

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、改造介面

@HystrixCommand(fallbackMethod = "timeOutError")

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @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,@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、針對介面配置熔斷方法

/**
 * 該方法是熔斷回撥方法，引數需要和介面保持一致
 * @param request
 * @param response
 * @param num
 * @return
 */
public JsonResult fallbackMethod(HttpServletRequest request,@RequestParam Integer num) {
  response.setStatus(500);
  log.info("發生了熔斷！！");
  return JsonResult.error("熔斷");
}

3.2.4、配置預設策略

hystrix:
 command:
  default:
   execution:
    isolation:
     strategy: THREAD
     thread:
      # 執行緒超時15秒,呼叫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),並且出錯率在50%以上,開啟斷路器.斷開服務,呼叫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。

叢集監控需要用到註冊中心

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、改造介面

@RequestMapping("/get")
@ResponseBody
//@TimeLimiter(name = "BulkheadA",fallbackMethod = "fallbackMethod")
@CircuitBreaker(name = "BulkheadA",fallbackMethod = "fallbackMethod")
@Bulkhead(name = "BulkheadA",fallbackMethod = "fallbackMethod")
public JsonResult allInfos(HttpServletRequest request,@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、針對介面配置熔斷方法

/**
 * 需要引數一致，並且加上相應異常
 * @param request
 * @param response
 * @param num
 * @param exception
 * @return
 */
public JsonResult fallbackMethod(HttpServletRequest request,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

配置的規則可以被程式碼覆蓋

3.3.5、配置監控

如grafana等

肆、關注點

• 是否需要過濾部分異常
• 是否需要全域性預設規則
• 可能需要引入其他中介軟體
• k8s流量控制
• 規則儲存和動態修改
• 接入改造代價
  

【後面的話】

個人建議的話，比較推薦sentinel，它提供了很多介面便於開發者自己拓展，同時我覺得他的規則動態更新也比較方便。最後是相關示例程式碼:單體應用示例程式碼

以上就是淺析Spring Boot單體應用熔斷技術的使用的詳細內容，更多關於Spring Boot單體應用熔斷技術的資料請關注我們其它相關文章！