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5.Spring Cloud初相识-------Hystrix熔断器

前言：

1.介绍Hystrix

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

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!"
05-12 02:42
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