016 服务容错 Spring Cloud Hystrix

素颜马尾好姑娘i 2022-03-09 11:00 251阅读 0赞

## Spring Cloud Hystrix ##

*  防雪崩利器
 *  基于Netflix对应的Hystrix
 *  服务降级
 *  依赖隔离
 *  服务熔断
 *  监控（Hystrix Dashboard）

#### 服务降级 ####

*  优先核心服务，非核心服务不可用或弱可用
 *  通过HystrixCommand注解指定
 *  fallbackMethod(回退函数)中具体实现降级逻辑

## 一、添加服务容错 ##

##### 1.Finchley.RELEASE添加Maven依赖 #####

<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    </dependency>

##### 2.启动类添加注解 #####

@EnableCircuitBreaker

或

@SpringCloudApplication
    
    包含：
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableCircuitBreaker

##### 3.添加 @HystrixCommand(fallbackMethod = “fallback”)注解 #####

1.指定方法降级

例：
    
     @HystrixCommand(fallbackMethod = "fallback")
     @GetMapping("/getProductInfoList")

2.默认降级

例：
    
    @RestController
    @DefaultProperties(defaultFallback = "defaultFallback")
    
    在加:
    @HystrixCommand

## 二、超时设置 ##

@HystrixCommand(commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
    })
    @GetMapping("/getProductInfoList"){
        ...
    }

配置方式实现

*  1.添加注解

@HystrixCommand

*  2.添加配置文件

hystrix:
      command:
        default:
          execution:
            isolation:
              thread:
                timeoutInMilliseconds: 3000

可单独设置指定方法超市时间，例:getProductInfoList

hystrix:
      command:
        default:
          execution:
            isolation:
              thread:
                timeoutInMilliseconds: 1000
        getProductInfoList:
          execution:
            isolation:
              thread:
                timeoutInMilliseconds: 3000

## 三、断路器模式-服务熔断 ##

@HystrixCommand(commandProperties = {
        @HystrixProperty(name = "circuitBreaker.enabled", value = "true"), // 开启熔断机制
        @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"), // 设置当请求失败的数量达到10个后，打开断路器，默认值为20
        @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000"), // 设置打开断路器多久以后开始尝试恢复，默认为5s
        @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "60"),  // 设置出错百分比阈值，当达到此阈值后，打开断路器，默认50%
    })
    @GetMapping("/getProductInfoList")
    public String getProductInfoList(@RequestParam("number") Integer number){
        ...
    }

## 四、feign-hystrix的使用 ##

首先打开feign-hystrix

feign:
      hystrix:
        enabled: true

添加降级回调函数

*  ProductClientFallback.class

@FeignClient(name = "product",fallback = ProductClient.ProductClientFallback.class)
    public interface ProductClient {
    
        @PostMapping("/product/listForOrder")
        List<ProductInfoOutput> listForOrder(@RequestBody List<String> productIdList);
    
        @PostMapping("/product/decreaseStock")
        void decreaseStock(@RequestBody List<DecreaseStockInput> decreaseStockInputList);
    
    
        @Component
        static  class ProductClientFallback implements ProductClient{
    
            @Override
            public List<ProductInfoOutput> listForOrder(List<String> productIdList) {
                return null;
            }
    
            @Override
            public void decreaseStock(List<DecreaseStockInput> decreaseStockInputList) {
    
            }
        }
    }

## 五、界面化 ##

#### 1.添加依赖 ####

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

#### 2.启动类添加注解 ####

@EnableHystrixDashboard

#### 3.访问hystrix ####

http://localhost:8081/hystrix

#### 4.单服务监控 ####

有：actuator

http://localhost:8081/hystrix/actuator/hystrix.stream