5.Spring Cloud初相识-------Hystrix熔断器
2024-09-21 13:01:15
前言：
1.介绍Hystrix
在一个分布式系统里，许多依赖不可避免的会调用失败，比如超时、异常等，如何能够保证在一个依赖出问题的情况下，不会导致整体服务失败，这个就是Hystrix需要做的事情。Hystrix提供了熔断、隔离、Fallback、cache、监控等功能，能够在一个、或多个依赖同时出现问题时保证系统依然可用。
2.为什么使用Hystrix
在分布式系统架构中多个系统之间通常是通过远程RPC调用进行通信，也就是 A 系统调用 B 系统服务，B 系统调用 C 系统的服务。当尾部应用 C 发生故障而系统 B 没有服务降级时候可能会导致 B，甚至系统 A 瘫痪，这种现象被称为雪崩现象。所以在系统设计时候要使用一定的降级策略，来保证当服务提供方服务不可用时候，服务调用方可以切换到降级后的策略进行执行。
实战：
1.新建服务消费者：
（1）添加依赖
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xm.cloud</groupId>
<artifactId>cl_hello_consumer_hy</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>cl_hello_consumer_hy</name>
<description>This is a Web about springcloud</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</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-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</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>
</project>
（2）修改配置
eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/
eureka.client.register-with-eureka=false
feign.hystrix.enabled=true
（3）开启注解
package com.xm.cloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication
public class ClHelloConsumerHyApplication {
public static void main(String[] args) {
SpringApplication.run(ClHelloConsumerHyApplication.class, args);
}
}
（4）配置熔断回调工厂
package com.xm.cloud.fallback;
import org.springframework.stereotype.Component;
import com.xm.cloud.service.HelloService;
import feign.hystrix.FallbackFactory;
@Component
public class HelloServiceFallbackFactory implements FallbackFactory<HelloService> {
@Override
public HelloService create(Throwable cause) {
return new HelloService() {
@Override
public String sayHello() {
return "HelloService 异常！";
}
};
}
}
（5）新建Service
package com.xm.cloud.service;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import com.xm.cloud.fallback.HelloServiceFallbackFactory;
@FeignClient(value="CL-HELLO-PRODUCER",fallbackFactory=HelloServiceFallbackFactory.class)
public interface HelloService {
@GetMapping("/hello")
public String sayHello();
}
（6）新建Controller
package com.xm.cloud.controller;
import java.util.ArrayList;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.xm.cloud.service.HelloService;
@RestController
public class HelloController {
@Autowired
private HelloService helloService;
@GetMapping("/hello")
public List<String> sayHello() {
List<String> list = new ArrayList<String>();
for(int i=0;i<10;i++) {
list.add(helloService.sayHello());
}
return list;
}
}
2.新建服务提供者：
（1）添加依赖
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xm.cloud</groupId>
<artifactId>cl_hello_producer_hy</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>cl_hello_producer_hy</name>
<description>This is a Web about springcloud</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</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-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>
</project>
（2）修改配置
server.port=8001
spring.application.name=cl-hello-producer
eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/
（3）开启注解
package com.xm.cloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@EnableDiscoveryClient
@EnableCircuitBreaker
@SpringBootApplication
public class ClHelloProducerHyApplication {
public static void main(String[] args) {
SpringApplication.run(ClHelloProducerHyApplication.class, args);
}
}
（4）新建Controller
package com.xm.cloud.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
@RestController
public class HelloController {
@GetMapping("/hello")
@HystrixCommand
public String sayHello() {
if(Math.random()>0.5) {
throw new RuntimeException();
} else {
return "Hello spring cloud!";
}
}
}
3.测试
运行：localhost:8080/hello
| 0 | "HelloService 异常！" |
|---|---|
| 1 | "Hello spring cloud!" |
| 2 | "HelloService 异常！" |
| 3 | "Hello spring cloud!" |
| 4 | "Hello spring cloud!" |
| 5 | "Hello spring cloud!" |
| 6 | "Hello spring cloud!" |
| 7 | "Hello spring cloud!" |
| 8 | "HelloService 异常！" |
| 9 | "Hello spring cloud!" |
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