Ribbon&Hystrix

EurekaServer

在微服务架构中，我们是讲一个单体应用拆分成多个服务单元，各个服务单元之间通过注册中心彼此发现和小菲对方提供的服务，每个服务单元都是单独部署，在各自的服务进程中进行，服务之间通过远程调用实现信息交互，那么当某个服务的响应太慢或者故障，又或者因为网络波动活故障，则会造成调用者延迟活调用失败，当大量请求到达，则会造成请求的堆积，导致调用者的线程挂起，从而引发调用者也无法响应，调用者也发生故障。

比如电商中的用户下订单，我们有两个服务，一个下订单服务，一个减库存服务，当用户下订单时调用下订单服务，然后下订单服务又调用减库存服务，如果减库存服务响应延迟或者没有响应，则会造成下订单服务的线程挂起等待，如果大量的用户请求下订单，或导致大量的请求堆积，引起下订单服务也不可用，如果还有另外一个服务依赖于下订单服务，比如用户服务，它需要查询用户订单，那么用户服务查询订单也会引起大量的延迟和请求堆积，导致服务也不可用。

所以在微服务架构中，很容易造成服务故障的蔓延，引发整个微服务系统瘫痪不可用。

为了解决此问题，微服务架构中映入了一种叫熔断器的服务保护机制。

熔断器也叫断路器，他们表示同一个意思，最早来源于微服务之父Martin Fowler的论文CircuitBreaker一文。“熔断器”本身是一种开关装置，用于在电路上保护线路过载，当线路中有电器发生短路时，能够及时切断故障电路，防止发生过载、发热甚至期货等严重后果。

微服务架构中的熔断器，就是当被调用放没有响应，想调用方直接返回一个村务响应即可，而不是长时间等待，这样避免调用时因为等待而线程一直得不到释放，避免故障在分布式系统间蔓延。

SpringCloud Hystrix实现了断路器、线程隔离等一系列服务保护功能。改功能也是基于Netflix的开源框架Hystrix实现的，该框架的目标在于通过控制那些访问远程系统、服务和第三方库的节点，从而对延迟和故障提供更强大的容错能力。Hystrix具备服务降级、服务熔断、线程和信号隔离、请求缓存、请求合并以及服务监控等强大功能。

 超时设置

忽略异常

 

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.work</groupId>
    <artifactId>eurekaserver</artifactId>
    <version>1.0.0</version>
    <name>eurekaserver</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>
View Code

application.yml

server:
  port: 8761

spring:
  application:
    name: EUREKASERVER
View Code

EurekaserverApplication.java

package com.work.eurekaserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaserverApplication {

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

}
View Code

EurekaClient1

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.work</groupId>
    <artifactId>eurekaclient1</artifactId>
    <version>1.0.0</version>
    <name>eurekaclient1</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>
View Code

application.yml

server:
  port: 8762
spring:
  application:
    name: client-8762

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/
View Code

Eurekaclient1Application.java

package com.work.eurekaclient1;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class Eurekaclient1Application {

    public static void main(String[] args) {
        SpringApplication.run(Eurekaclient1Application.class, args);
    }

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }

}
View Code

RibbonController.java

package com.work.eurekaclient1.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.RestTemplate;

@Controller
public class RibbonController {

    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/loadInstance")
    @ResponseBody
    public String loadInstance(){
        ServiceInstance choose = this.loadBalancerClient.choose("client-87");
        System.out.println(choose.getServiceId()+":"+choose.getHost()+":"+choose.getPort());
        return choose.getServiceId()+":"+choose.getHost()+":"+choose.getPort();
    }
}
View Code

EurekaClient2

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.work</groupId>
    <artifactId>eurekaclient2</artifactId>
    <version>1.0.0</version>
    <name>eurekaclient2</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>
View Code

application.yml

server:
  port: 8763
spring:
  application:
    name: client-87

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/
View Code

Eurekaclient2Application.java

package com.work.eurekaclient2;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Eurekaclient2Application {

    public static void main(String[] args) {
        SpringApplication.run(Eurekaclient2Application.class, args);
    }

}
View Code

ClientController.java

package com.work.eurekaclient2.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class ClientController {
    @GetMapping("/getUser")
    @ResponseBody
    public String getUser(){
        System.out.println("获取用户成功");
        return "获取用户成功";
    }
}
View Code

启动顺序：

1.一次启动EurekaServer，EurekaClient1，EurekaClient2，

2.然后将EurekaClient2中的application.yml的server.port=8763改为server.port=8764，再次启动该项目；

3.打开EurekaServer的配置页面（http://localhost:8761/）

访问：http://localhost:8762/loadInstance

多次刷新可以看到页面变化

EurekaClient3

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.work</groupId>
    <artifactId>eurekaclient3</artifactId>
    <version>1.0.0</version>
    <name>eurekaclient3</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR8</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>


        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>
View Code

application.yml

server:
  port: 8765

spring:
  application:
    name: Hystrix-8765

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/
View Code

Eruekaclient3Application.java

package com.work.eurekaclient3;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableHystrix
public class Eurekaclient3Application {

    public static void main(String[] args) {
        SpringApplication.run(Eurekaclient3Application.class, args);
    }

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }

}
View Code

HystrixController.java

package com.work.eurekaclient3.controller;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.client.RestTemplate;

@Controller
public class HystrixController {

    @Autowired
    private RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "getDefaultUser")
    @RequestMapping("/getUser")
    @ResponseBody
    public String getUser(){
        return restTemplate.getForObject("http://client-87/getUser",String.class);
    }

    private String getDefaultUser(){
        System.out.println("熔断，默认毁掉函数");
        return "{"username":"admin","age":"-1"}";
    }
}
View Code

http://localhost:8765/getUser

关闭Eurekaclient2Application，再访问上述连接

【推广】 免费学中医，健康全家人
原文地址：https://www.cnblogs.com/LoganChen/p/14030317.html