Spring Cloud Feign和Hystric进行负载和熔断

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在Spring Cloud Netflix栈中，各个微服务都是以HTTP接口的形式暴露自身服务的，因此在调用远程服务时就必须使用HTTP客户端。我们可以使用JDK原生的URLConnection、Apache的Http Client、Netty的异步HTTP Client, Spring的RestTemplate。但是，用起来最方便、最优雅的还是要属Feign了。

Feign简介

Feign是一种声明式、模板化的HTTP客户端。在Spring Cloud中使用Feign, 我们可以做到使用HTTP请求远程服务时能与调用本地方法一样的编码体验，开发者完全感知不到这是远程方法，更感知不到这是个HTTP请求。

下面实现了Feign的熔断处理，先是pom.xml文件：

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<?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.fiveplus</groupId>
	<artifactId>user-feign</artifactId>
	<version>1.0.0-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>user-feign</name>
	<description>User project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.9.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>
	</properties>

	<dependencies>
		
		<!-- 部署热更新 -->
		<dependency>
		    <groupId>org.springframework.boot</groupId>
		    <artifactId>spring-boot-devtools</artifactId>
		    <optional>true</optional>
		    <scope>true</scope>
		</dependency>
		
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<optional>true</optional>
		</dependency>
	
		<dependency>
	    		<groupId>org.springframework.cloud</groupId>
	    		<artifactId>spring-cloud-starter-hystrix</artifactId>
		</dependency>

		<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
        </dependency>
	
		<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>Dalston.RC1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
    					<executable>true</executable>
  				</configuration>
			</plugin>
		</plugins>
	</build>
	
	<repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

接下来是application.properties项目配置文件：

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server.port=7000

eureka.client.service-url.default-zone=http://localhost:8761/eureka/

spring.application.name=user-feign

# open hystrix

feign.hystrix.enabled=true
  • eureka.client.service-url.default-zone 服务注册中心，上面的写法针对没有做安全模块的服务配置中心Eureka-Server，如果你的Eureka-Server实现了安全模块，写法为：http://username:password@ip:host/eureka/

Feign接口层

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package com.fiveplus.feign;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.fiveplus.entity.User;

@FeignClient(value="user-service")
public interface SchedualServiceUser {
	@RequestMapping(value = "/user/get.json",method = RequestMethod.GET)
	String get(@RequestParam("loginName") String loginName,@RequestParam("password") String password);
}
  • @FeignClient 对应微服务的application-name
  • 接口声明需要与服务提供者保持一致

Hystric熔断层

继承Feign接口层，实现方法，当Eureka注册中心中不存在目标服务对应的请求，那么会进行熔断处理，返回该实现方法的值。

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package com.fiveplus.hystric;

import org.springframework.stereotype.Component;
import com.fiveplus.feign.SchedualServiceUser;

@Component
public class SchedualServiceUserHystric implements SchedualServiceUser{
	private String msg = "error";
	public String get(String loginName, String password) {
		return msg;
	}
}

RestController对外开放

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package com.fiveplus.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.fiveplus.feign.SchedualServiceUser;

@RestController
public class UserController {
	@Autowired
	private SchedualServiceUser schedualServiceUser;
	
	@RequestMapping(value = "/user/get.json",method = RequestMethod.GET)
	public String get(@RequestParam("loginName") String loginName,@RequestParam("password") String password) {
		return schedualServiceUser.get(loginName, password);
	}
}

启动类Application.java

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package com.fiveplus;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
@EnableHystrix
@EnableHystrixDashboard
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
	@Bean
	@LoadBalanced
	RestTemplate restTemple() {
		return new RestTemplate();
	}
	
}

结束

在实际使用过程中，也许不需要对外提供服务，依据详细情况具体制定。

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