1. 什么是微服务?
“微服务”一词来自国外的一篇博文,网站:https://martinfowler.com/articles/microservices.html
如果您不能看懂英文文档,可以跳转到搜简体中文的文档
这是国人翻译的文档,可以学习参考:
引用官方文档解释:
简单来说,微服务架构风格[1]是一种将一个单一应用程序开发为一组小型服务的方法,每个服务运行在自己的进程中,服务间通信采用轻量级通信机制(通常用HTTP资源API)。这些服务围绕业务能力构建并且可通过全自动部署机制独立部署。这些服务共用一个最小型的集中式的管理,服务可用不同的语言开发,使用不同的数据存储技术。
2. 什么是Spring Cloud?
Spring Cloud是一个分布式的整体解决方案的框架。基于Spring Boot开发。Spring Cloud 为开发者提供了在分布式系统(配置管理,服务发现,负载,网关,消息总线,集群管理,安全管理,分布式锁,分布式事务等等)中快速构建的工具,使用Spring Cloud的开发者可以快速的启动服务或构建应用、同时能够快速和云平台资源进行对接。
3. 什么是Spring Cloud Eureka?
Spring Cloud Eureka 是 Spring Cloud Netflix 微服务套件的一部分,基于 Netflix Eureka 做了二次封装,主要负责实现微服务架构中的服务治理功能。
Spring Cloud Eureka 是一个基于 REST 的服务,并且提供了基于 Java 的客户端组件,能够非常方便地将服务注册到 Spring Cloud Eureka 中进行统一管理。
4. Eureka服务注册中心
Eureka server:创建服务注册中心
环境准备:
JDK 1.8
SpringBoot2.2.3
SpringCloud(Hoxton.SR6)
Maven 3.2+
开发工具
IntelliJ IDEA
smartGit
创建一个SpringBoot Initialize项目
pom,加上spring-cloud-starter-netflix-eureka-server
org.springframework.cloud spring-cloud-starter-netflix-eureka-server
@EnableEurekaServer配置Eureka服务端:
package com.example.springcloud.server; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer; @SpringBootApplication @EnableEurekaServer public class SpringcloudEurekaServerApplication { public static void main(String[] args) { SpringApplication.run(SpringcloudEurekaServerApplication.class, args); } }
eureka服务端配置:
spring: application: name: eurka-server server: port: 8761 eureka: instance: hostname: localhost client: register-with-eureka: false fetch-registry: false service-url: defaultZone: http://localhost:8761/eureka/
启动项目,访问:http://localhost:8761
5. Eureka服务提供者
在Eureka中,服务提供者和服务消费者是Eureka client提供的,使用注解@EnableEurekaClient标明
新建SpringBoot Initializer项目
server: port: 8081 spring: application: name: eureka-service-provider eureka: client: service-url: defaultZone: http://localhost:8761/eureka/ register-with-eureka: true fetch-registry: true healthcheck: enabled: false instance: status-page-url-path: http://localhost:8761/actuator/info health-check-url-path: http://localhost:8761/actuator//health prefer-ip-address: true instance-id: eureka-service-provider8081
写个例子,以github用户为例:
package com.example.springcloud.provider.bean; import com.fasterxml.jackson.annotation.JsonIgnoreProperties; import lombok.Data; import java.io.Serializable; /** * * * */ @JsonIgnoreProperties(ignoreUnknown = true) @Data public class User implements Serializable { private String name; private String blog; @Override public String toString() { return "User{" + "name='" + name + '\'' + ", blog='" + blog + '\'' + '}'; } }
读取github用户信息:
package com.example.springcloud.provider.service; import com.example.springcloud.provider.bean.User; import lombok.extern.slf4j.Slf4j; import org.springframework.boot.web.client.RestTemplateBuilder; import org.springframework.stereotype.Service; import org.springframework.web.client.RestTemplate; /** * * * */ @Service @Slf4j public class UserService { private final RestTemplate restTemplate; public UserService(RestTemplateBuilder restTemplateBuilder) { this.restTemplate = restTemplateBuilder.build(); } public User findUser(String user) throws InterruptedException { log.info("username[{}]" , user); String url = String.format("https://api.github.com/users/%s", user); User results = restTemplate.getForObject(url, User.class); return results; } }
@EnableEurekaClient指定eureka client:
package com.example.springcloud.provider; import com.example.springcloud.provider.bean.User; import com.example.springcloud.provider.service.UserService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.ResponseBody; import org.springframework.web.bind.annotation.RestController; @SpringBootApplication @EnableEurekaClient @RestController public class SpringcloudServiceProviderApplication { @Autowired UserService userService; public static void main(String[] args) { SpringApplication.run(SpringcloudServiceProviderApplication.class, args); } @GetMapping({"/api/users/{username}"}) @ResponseBody public User findUser(@PathVariable("username")String username) throws InterruptedException{ User user= userService.findUser(username); return user; } }
部署后,注册信息发布到eureka server:
服务注册信息打印到控制台
访问接口:http://localhost:8081/api/users/mojombo,能访问就是注册成功
提示:EMERGENCY! EUREKA MAY BE INCORRECTLY CLAIMING INSTANCES ARE UP WHEN THEY'RE NOT. RENEWALS ARE LESSER THAN THRESHOLD AND HENCE THE INSTANCES ARE NOT BEING EXPIRED JUST TO BE SAFE.
SpringCloud警告(Eureka):EMERGENCY! EUREKA MAY BE INCORRECTLY CLAIMING INSTANCES ARE UP WHEN THEY'RE NOT. RENEWALS ARE LESSER THAN THRESHOLD AND HENCE THE INSTANCES ARE NOT BEING EXPIRED JUST TO BE SAFE.
警告!Eureka可能存在维护了错误的实例列表(当它们没有启动的时候,Eureka却把它当成启动的了);Renews值小于Threshold值,因此剩下未过期的都是安全的。
方法:参考博客https://www.cnblogs.com/gudi/p/8645370.html,可以关了eureka的自我保护模式eureka.server.enableSelfPreservation=false
eureka也引用SpringBoot actuator监控管理,SpringBoot actuator可以参考我之前博客:SpringBoot系列之actuator监控管理极速入门与实践
具体可以进行配置,配置成eureka server的ip,加上actuator
eureka: instance: status-page-url-path: http://localhost:8761/actuator/info health-check-url-path: http://localhost:8761/actuator/health
显示ip和实例id配置:
6. Eureka服务消费者
Spring cloud有两种最常用的服务调用方式,一种是ribbon+restTemplate,另一种是feign,所以本博客以学习为目的,简单介绍一下ribbon+restTemplate的方式,之后有时间再介绍feign的方式
ribbon+resttemplate方式,Spring Cloud Hoxton.SR6版本不需要引入spring-cloud-starter-netflix-ribbon,已经默认集成
引入web既可,主要是想调restTemplate
org.springframework.boot spring-boot-starter-web
yaml配置:
server: port: 8082 spring: application: name: eureka-service-consumer eureka: client: service-url: defaultZone: http://localhost:8761/eureka/ fetch-registry: true register-with-eureka: false healthcheck: enabled: false instance: status-page-url-path: http://localhost:8761/actuator/info health-check-url-path: http://localhost:8761/actuator//health prefer-ip-address: true instance-id: eureka-service-consumer8082
关键点,使用SpringCloud的@LoadBalanced,才能调http://EUREKA-SERVICE-PROVIDER/api/users/? 接口的数据,浏览器是不能直接调的
package com.example.springcloud.consumer; import com.example.springcloud.consumer.bean.User; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.context.annotation.Bean; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate; @SpringBootApplication @EnableEurekaClient @RestController public class SpringcloudServiceConsumerApplication { @Bean @LoadBalanced public RestTemplate restTemplate(){ return new RestTemplate(); } public static void main(String[] args) { SpringApplication.run(SpringcloudServiceConsumerApplication.class, args); } @GetMapping("/findUser/{username}") public User index(@PathVariable("username")String username){ return restTemplate().getForObject("http://EUREKA-SERVICE-PROVIDER/api/users/"+username,User.class); } }