Hystrix学习笔记

2024-01-30 15:38:10

第一章 Hystrix熔断器介绍

Hystrix是Netflix公司开源的一个项目，提供了熔断器功能，能够阻止分布式系统中出现联动故障。

Hystrix是通过隔离服务的访问点阻止联动故障的，并提供了故障的解决方案，从而提供整个分布式系统的弹性。

1.1. Hystrix设计原则

防止单个服务的故障耗尽整个服务的servlet容器的线程资源
快速失败机制，如果某个服务出现故障，调用该服务的请求快速失败，而不是线程等待
提供回退方案（fallback），请求发生故障时，提供设定好的回退方案
使用熔断机制，防止故障扩散到其他服务
提供监控组件Hystrix Dashbord，实时监控熔断器的状态

1.2. Hystrix工作机制

当服务的API接口的失败次数在一定时间内小于设定的阀值时，熔断器处于关闭状态。正常提供服务。
当服务的API接口的失败次数在一定时间内大于设定的阀值时，打开熔断器，执行快速失败逻辑，不执行业务逻辑，请求线程不会处于阻塞状态。
处于打开状态的熔断器，一段时间后会处于半打开状态，并将一定数量的请求执行正常逻辑，剩余请求执行快速失败。若执行正常逻辑的请求失败了，熔断器继续打开，如果成功了，将熔断器关闭，既熔断器的修复功能。

第二章 Ribbon和RestTemplate结合时使用熔断器

2.1. 引入依赖

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>

</dependency>

旧版本为：spring-cloud-starter-hystrix

2.2. 启动器

开启熔断器功能：

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@EnableEurekaClient
@EnableHystrix 
public class ConsumerApplication {
    
    public static void main(String[] args) throws Exception {
        SpringApplication.run(ConsumerApplication.class, args);
    }

}

2.3. 熔断器

引入fallbackMethod 和编写fallback method

@RequestMapping("/cust/get/{id}")
    @HystrixCommand(fallbackMethod = "getCustInfoByIdFallback")
    public CustInfo getCustInfoById(@PathVariable("id") Long id) {
        log.debug("Consumer_CustInfoController getCustInfoById is running...");
        return restTemplate.getForObject(PROVIDER_PRIFIX + "/cust_info/selectid/" + id, CustInfo.class);
    }
    public CustInfo getCustInfoByIdFallback(@PathVariable("id") Long id) {
        CustInfo custInfo = new CustInfo();
        custInfo.setId(id);
        custInfo.setUsername("fallback");
        return custInfo;
    }

第三章 Ribbon和Feign结合时使用熔断器

3.1. 引入依赖

Feign的起步依赖中已经引入了Hystrix的依赖，所有不需要引入依赖了。

3.2. Yml配置

开启hystrix功能：

feign:
  hystrix:
    enabled: true

3.3. 在FeignClient中引入fallback类

3.3.1. 用fallback时

@FeignClient(value = "EUREKA-PROVIDER", configuration = FeignConfig.class,fallback = CustEurekaClientFeignFallback.class)
public interface CustEurekaClientFeign {
    
    @GetMapping("/cust_info/selectid/{id}")
    public String getCustInfoById(@RequestParam(value="id") Long id);
    
    @GetMapping("/cust_info/getServerInfo")
    public String getServerInfo();
}

3.3.2. 当用FallbackFactory时

@FeignClient(value = "EUREKA-PROVIDER", configuration = FeignConfig.class,fallbackFactory =  CustEurekaClientFeignFallbackFactory.class)
public interface CustEurekaClientFeign {
    
    @GetMapping("/cust_info/selectid/{id}")
    public String getCustInfoById(@RequestParam(value="id") Long id);
    
    @GetMapping("/cust_info/getServerInfo")
    public String getServerInfo();
}

3.4. 编写Fallback类

3.4.1. 用fallback时

@Component
public class CustEurekaClientFeignFallback implements CustEurekaClientFeign{

    @Override
    public String getCustInfoById(Long id) {
        
        return "getCustInfoById is fall, this is hystrix back info for id:" + id;
    }

    @Override
    public String getServerInfo() {
        
        return "getServerInfo is fall, this is hystrix back info";
    }

}

3.4.2. 当用FallbackFactory时

@Component
public class CustEurekaClientFeignFallbackFactory implements FallbackFactory<CustEurekaClientFeign>{

    @Override
    public CustEurekaClientFeign create(Throwable cause) {
        
        return new CustEurekaClientFeign() {

            @Override
            public String getCustInfoById(Long id) {
                
                return "getCustInfoById is fall, this is hystrix back info for id:" + id;
            }

            @Override
            public String getServerInfo() {
                
                return "getServerInfo is fall, this is hystrix back info";
            }
            
        };
    }

}

第四章 RestTemplate中使用Hystrix dashboard

4.1. 引入依赖

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

4.2. 启动器

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@EnableEurekaClient
@EnableHystrix 
@EnableHystrixDashboard 
public class ConsumerApplication {
    
    public static void main(String[] args) throws Exception {
        SpringApplication.run(ConsumerApplication.class, args);
    }

}

4.3. 访问

http://127.0.0.1/hystrix.stream

http://127.0.0.1/hystrix

第五章 Feign中使用hystrix dashboard

5.1. 引入依赖

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

为什么还要引入spring-cloud-starter-netflix-hystrix？

因为Feign中引入的不是hystrix起步依赖

5.2. 启动器

加入@EnableHystrixDashboard

第六章 Turbine聚合监控

新建工程：

turbine-actuator

6.1. 引入依赖

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

6.2. 启动器

@SpringBootApplication
@EnableTurbine
public class Turbine_StartSpringCloudApp {

        public static void main(String[] args) throws Exception {
            SpringApplication.run(Turbine_StartSpringCloudApp.class, args);
        }
}

6.3. Yml配置

server:
  port: 8700

spring:
  application:
    name: turbind-actuator

  
eureka:
  client:
    registerWithEureka: true
    fetchRegistry: true 
    serviceUrl:
      defaultZone: 
        http://eureka-server-7001:7001/eureka/
  instance:
    instance-id: turbind-actuator-8700
    prefer-ip-address: true
    
turbine:
  aggregator:
    clusterConfig: default
  appConfig: eureka-provider,consumer-80
  clusterNameExpression: new String("default")

6.4. 访问