Eureka服务注册与发现
什么是Eureka
Netflix 在设计Eureka 时,遵循的就是AP原则
CAP原则又称CAP定理,指的是在一个分布式系统中
一致性(Consistency)可用性(Availability)
分区容错性(Partition tolerance)
CAP 原则指的是,这三个要素最多只能同时实现两点,不可能三者兼顾。
Eureka是Netflix的一个子模块,也是核心模块之一。Eureka是一个基于REST的服务,用于定位服务, 以实现云端中间层服务发现和故障转移,服务注册与发现对于微服务来说是非常重要的,有了服务发现 与注册,只需要使用服务的标识符,就可以访问到服务,而不需要修改服务调用的配置文件了,功能类 似于Dubbo的注册中心,比如Zookeeper;
原理讲解
Eureka的基本架构:
SpringCloud 封装了NetFlix公司开发的Eureka模块来实现服务注册和发现
Eureka采用了C-S的架构设计,EurekaServer 作为服务注册功能的服务器,
他是服务注册中心 而系统中的其他微服务。使用Eureka的客户端连接到EurekaServer并维持心跳连接。这样系统的维护人 员就可以通过EurekaServer来监控系统中各个微服务是否正常运行,SpringCloud的一些其他模块(比 如Zuul)就可以通过EurekaServer来发现系统中的其他微服务,并执行相关的逻辑;
Eureka 包含两个组件:Eureka Server 和 Eureka Client 。
Eureka Server 提供服务注册服务,各个节点启动后,会在EurekaServer中进行注册,这样Eureka Server中的服务注册表中将会存储所有可用服务节点的信息,服务节点的信息可以在界面中直观的看到。
和Dubbo架构对比:
Eureka Client是一个Java客户端,用于简化EurekaServer的交互,客户端同时也具备一个内置的,使用 轮询负载算法的负载均衡器。在应用启动后,将会向EurekaServer发送心跳(默认周期为30秒)。如果 Eureka Server在多个心跳周期内没有接收到某个节点的心跳,EurekaServer将会从服务注册表中把这 个服务节点移除掉(默认周期为90秒)
三大角色
- Eureka Server:提供服务的注册于发现
- Service Provider:将自身服务注册到Eureka中,从而使消费方能够找到。
- Service Consumer:服务消费方从Eureka中获取注册服务列表,从而找到消费服务。
Eureka服务构建
建立spring-cloud-eureka-7001模块(导入依赖)
<?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">
<parent>
<artifactId>spring-cloud-demo</artifactId>
<groupId>top.tk.springcloud</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>spring-cloud-eureka-7001</artifactId>
<dependencies>
<!-- eureka-server服务端 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka-server</artifactId>
<version>1.4.7.RELEASE</version>
</dependency>
<!--热部署-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<!--lombok-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
</project>
在当前模块的resources下新建application.yml
server:
port: 7001
#Eureka配置
eureka:
instance:
hostname: localhost #eureka服务端的实例名称
client:
register-with-eureka: false # 是否将自己注册到Eureka服务器中,本身是服务器,无需注册
fetch-registry: false # false表示自己端就是注册中心,我的职责就是维护服务实例,并不需要去检索服务
service-url:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
#设置与Eureka Server交互的地址查询服务和注册服务都需要依赖这个defaultZone地址
新建EurekaApplication_7001启动类
package top.tk.springcloud;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.Environment;
import java.net.InetAddress;
import java.net.UnknownHostException;
/**
* @ClassName: EurekaApplication
* @Author: campsis-tk
* @Date: 2020/8/26 8:57
* @Description:
**/
@Slf4j
@SpringBootApplication
@EnableEurekaServer //EurekaServer服务器端启动类,接受其他微服务注册进来!
public class EurekaApplication_7001 {
public static void main(String[] args) throws UnknownHostException {
ConfigurableApplicationContext application = SpringApplication.run(EurekaApplication_7001.class, args);
//打印信息
Environment env = application.getEnvironment();
String ip = InetAddress.getLocalHost().getHostAddress();
String port = env.getProperty("server.port"); //端口
String path = env.getProperty("server.servlet.context-path"); //根路径
String hj = env.getProperty("spring.profiles.active"); //环境
log.info("
----------------------------------------------------------
" +
"Application Tk Cloud is running! Access URLs:
" +
"IP: " + ip + "
" +
"Port: " + port + "
" +
"Local: http://localhost:" + port + "/
" +
"当前配置环境: 当前环境为:" + hj + "
" +
"----------------------------------------------------------");
}
}
spring-cloud-eureka-7001模块结构
启动,访问测试:http://localhost:7001/
System Status:系统信息
DS Replicas:服务器副本
Instances currently registered with Eureka:已注册的微服务列表
General Info:一般信息
Instance Info:实例信息
将 spring-cloud-provider-6001的服务入驻到 spring-cloud-eureka-7001的eureka中!
修改spring-cloud-provider-6001服务的pom文件,增加eureka的支持!
<?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">
<parent>
<artifactId>spring-cloud-demo</artifactId>
<groupId>top.tk.springcloud</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>spring-cloud-provider-6001</artifactId>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>6</source>
<target>6</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<!--引入自定义的模块,我们就可以使用这个模块中的类了-->
<dependency>
<groupId>top.tk.springcloud</groupId>
<artifactId>spring-cloud-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-test</artifactId>
</dependency>
<!-- spring-boot-devtools -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<!--将服务的provider注册到eureka中(新增此处)-->
<!-- https://mvnrepository.com/artifact/org.springframework.cloud/springcloud-starter-eureka -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
<version>1.4.7.RELEASE</version>
</dependency>
</dependencies>
</project>
修改spring-cloud-provider-6001的yaml中配置eureka 的支持
#端口
server:
port: 6001
#mybatis配置
mybatis:
type-aliases-package: top.tk.tk.springcloud.pojo
mapper-locations: classpath:mybatis/mapper/*.xml
config-location: classpath:mybatis/mybatis-config.xml
#Spring配置
spring:
application:
name: springcloud-provider-user
datasource:
type: com.alibaba.druid.pool.DruidDataSource #数据源
driver-class-name: org.gjt.mm.mysql.Driver
url: jdbc:mysql://localhost:3306/springcloud-db?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
username: root
password: root
#eureka配置
eureka:
client:
service-url:
defaultZone: http://localhost:7001/eureka
修改spring-cloud-provider-6001的主启动类注解支持
package top.tk.springcloud;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.Environment;
import java.net.InetAddress;
import java.net.UnknownHostException;
/**
* @ClassName: UserProviderApplication_6001
* @Author: campsis-tk
* @Date: 2020/8/25 14:07
* @Description: 启动类
**/
@Slf4j
@SpringBootApplication
@EnableDiscoveryClient //服务发现
@EnableEurekaClient // 本服务启动之后会自动注册进Eureka中!
public class UserProviderApplication_6001 {
public static void main(String[] args) throws UnknownHostException {
ConfigurableApplicationContext application = SpringApplication.run(UserProviderApplication_6001.class, args);
//打印信息
Environment env = application.getEnvironment();
String ip = InetAddress.getLocalHost().getHostAddress();
String port = env.getProperty("server.port"); //端口
String path = env.getProperty("server.servlet.context-path");//根路径
String hj = env.getProperty("spring.profiles.active"); //环境
log.info("
----------------------------------------------------------
" +
"Application Tk Cloud is running! Access URLs:
" +
"IP: " + ip + "
" +
"Port: " + port + "
" +
"Local: http://localhost:" + port + "/
" +
"当前配置环境: 当前环境为:" + hj + "
" +
"----------------------------------------------------------");
}
}
服务端,客户端都创建好了,先启动7001,再启动6001,测试访问
actuator与注册微服务信息完善
主机名称:服务名称修改
在spring-cloud-provider-6001的yaml中修改一下配置
#端口
server:
port: 6001
#mybatis配置
mybatis:
type-aliases-package: top.tk.tk.springcloud.pojo
mapper-locations: classpath:mybatis/mapper/*.xml
config-location: classpath:mybatis/mybatis-config.xml
#Spring配置
spring:
application:
name: springcloud-provider-user
datasource:
type: com.alibaba.druid.pool.DruidDataSource #数据源
driver-class-name: org.gjt.mm.mysql.Driver
url: jdbc:mysql://localhost:3306/springcloud-db?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
username: root
password: root
#eureka配置
eureka:
client:
service-url:
defaultZone: http://localhost:7001/eureka
#此处做修改
instance:
instance-id: springcloud-provider-user-6001 # 重点,和client平级
先启动7001,再启动6001,测试访问
访问信息有IP信息提示
修改spring-cloud-provider-6001的yml配置
#eureka配置
eureka:
client:
service-url:
defaultZone: http://localhost:7001/eureka
instance:
instance-id: springcloud-provider-user-6001 # 重点,和client平级
#修改了此处
prefer-ip-address: true # true访问路径可以显示IP地址
测试,ip显示成功
info内容的构建
修改6001的pom文件,新增依赖!
<?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">
<parent>
<artifactId>spring-cloud-demo</artifactId>
<groupId>top.tk.springcloud</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>spring-cloud-provider-6001</artifactId>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>6</source>
<target>6</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<!--引入自定义的模块,我们就可以使用这个模块中的类了-->
<dependency>
<groupId>top.tk.springcloud</groupId>
<artifactId>spring-cloud-api</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-test</artifactId>
</dependency>
<!-- spring-boot-devtools -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<!--将服务的provider注册到eureka中-->
<!-- https://mvnrepository.com/artifact/org.springframework.cloud/springcloud-starter-eureka -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
<version>1.4.7.RELEASE</version>
</dependency>
<!--actuator监控信息完善(新增此处)-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
</dependencies>
</project>
然后回到我们的spring-cloud-provider-6001的yaml配置文件中修改增加信息
#端口
server:
port: 6001
#mybatis配置
mybatis:
type-aliases-package: top.tk.tk.springcloud.pojo
mapper-locations: classpath:mybatis/mapper/*.xml
config-location: classpath:mybatis/mybatis-config.xml
#Spring配置
spring:
application:
name: springcloud-provider-user
datasource:
type: com.alibaba.druid.pool.DruidDataSource #数据源
driver-class-name: org.gjt.mm.mysql.Driver
url: jdbc:mysql://localhost:3306/springcloud-db?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
username: root
password: root
#eureka配置
eureka:
client:
service-url:
defaultZone: http://localhost:7001/eureka
instance:
instance-id: springcloud-provider-user-6001 # 重点,和client平级
prefer-ip-address: true # true访问路径可以显示IP地址
#此处新增
#配置info
info:
author.name: tk
company.name: campsis-tk
build.artifactId: spring-cloud-provider-6001
build.version: 1.0
打开info页面查看是否配置成功
Eureka的自我保护机制
如果出现的这些红色情况,没出现的,修改一个服务名,故意制造错误!
一句话总结:某时刻某一个微服务不可以用了,eureka不会立刻清理,依旧会对该微服务的信息进行保 存!
默认情况下,如果EurekaServer在一定时间内没有接收到某个微服务实例的心跳,EurekaServer将会注 销该实例(默认90秒)。但是当网络分区故障发生时,微服务与Eureka之间无法正常通行,以上行为可 能变得非常危险了--因为微服务本身其实是健康的,此时本不应该注销这个服务。Eureka通过 自我保护 机制 来解决这个问题--当EurekaServer节点在短时间内丢失过多客户端时(可能发生了网络分区故 障),那么这个节点就会进入自我保护模式。一旦进入该模式,EurekaServer就会保护服务注册表中的 信息,不再删除服务注册表中的数据(也就是不会注销任何微服务)。当网络故障恢复后,该 EurekaServer节点会自动退出自我保护模式。
在自我保护模式中,EurekaServer会保护服务注册表中的信息,不再注销任何服务实例。当它收到的心 跳数重新恢复到阈值以上时,该EurekaServer节点就会自动退出自我保护模式。它的设计哲学就是宁可 保留错误的服务注册信息,也不盲目注销任何可能健康的服务实例.
综上,自我保护模式是一种应对网络异常的安全保护措施。它的架构哲学是宁可同时保留所有微服务 (健康的微服务和不健康的微服务都会保留),也不盲目注销任何健康的微服务。使用自我保护模式, 可以让Eureka集群更加的健壮和稳定。 在SpringCloud中,可以使用 eureka.server.enable-self-preservation = false 禁用自我保护 模式 【不推荐关闭自我保护机制】
对于注册进eureka里面的微服务,可以通过服务发现来获得该服务的信息。【对外暴露服务】
修改spring-cloud-provider-6001工程中的UserController(新增一个info方法)
package top.tk.springcloud.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import top.tk.springcloud.pojo.User;
import top.tk.springcloud.service.UserService;
import java.util.List;
/**
* @ClassName: UserController
* @Author: campsis-tk
* @Date: 2020/8/25 14:04
* @Description: user控制器
**/
@RestController
@RequestMapping("/user") //根路径
public class UserController {
@Autowired
private UserService userService;
//注入DiscoveryClient获取服务信息
@Autowired
private DiscoveryClient client;
@GetMapping("/get/{id}")
public User get(@PathVariable("id") Integer id) {
return userService.selectByPrimaryKey(id);
}
@GetMapping("/list")
public List<User> queryAllUser() {
return userService.queryAllUser();
}
//新增此方法
@GetMapping("/info")
public Object info() {
//获得微服务列表清单
List<String> list = client.getServices();
System.out.println("client.getServices()==>" + list);
//得到一个具体的微服务!
List<ServiceInstance> serviceInstanceList = client.getInstances("springcloud-provider-user");
for (ServiceInstance serviceInstance : serviceInstanceList) {
System.out.println(
serviceInstance.getServiceId() + " " +
serviceInstance.getHost() + " " +
serviceInstance.getPort() + " " +
serviceInstance.getUri()
);
}
return this.client;
}
}
重启spring-cloud-provider-6001之后访问http://localhost:6001/user/info
修改主启动类(添加@EnableDiscoveryClient)
package top.tk.springcloud;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.Environment;
import java.net.InetAddress;
import java.net.UnknownHostException;
/**
* @ClassName: UserProviderApplication_6001
* @Author: campsis-tk
* @Date: 2020/8/25 14:07
* @Description: 启动类
**/
@Slf4j
@SpringBootApplication
@EnableDiscoveryClient //服务发现
@EnableEurekaClient // 本服务启动之后会自动注册进Eureka中!
public class UserProviderApplication_6001 {
public static void main(String[] args) throws UnknownHostException {
ConfigurableApplicationContext application = SpringApplication.run(UserProviderApplication_6001.class, args);
//打印信息
Environment env = application.getEnvironment();
String ip = InetAddress.getLocalHost().getHostAddress();
String port = env.getProperty("server.port");
String path = env.getProperty("server.servlet.context-path");
String hj = env.getProperty("spring.profiles.active");
log.info("
----------------------------------------------------------
" +
"Application Tk Cloud is running! Access URLs:
" +
"IP: " + ip + "
" +
"Port: " + port + "
" +
"Local: http://localhost:" + port + "/
" +
"当前配置环境: 当前环境为:" + hj + "
" +
"----------------------------------------------------------");
}
}
# consumer访问服务(spring-cloud-consumer-user-80)
修改UserConsumerController增加一个方法
package top.tk.springcloud.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import top.tk.springcloud.pojo.User;
import java.util.List;
/**
* @ClassName: UserConsumerController
* @Author: campsis-tk
* @Date: 2020/8/26 14:26
* @Description:
**/
@RestController
@RequestMapping("/consumer")
public class UserConsumerController {
//理解:消费者,不应该有service层
//使用RestTemplate访问restful接口非常的简单粗暴且无脑
//(url,requestMap,ResponseBean.class) 这三个参数分别代表
//REST请求地址,请求参数,Http响应转换 被 转换成的对象类型
@Autowired
private RestTemplate restTemplate;
private static final String REST_URL_PREFIX = "http://localhost:6001";
@RequestMapping("/user/get/{id}")
public User get(@PathVariable("id") Long id){
return restTemplate.getForObject(REST_URL_PREFIX+"/user/get/" + id,User.class);
}
@RequestMapping("/user/list")
public List<User> list(){
return restTemplate.getForObject(REST_URL_PREFIX+"/user/list",List.class);
}
//新增此方法
@GetMapping("/user/info")
public Object info(){
return restTemplate.getForObject(REST_URL_PREFIX+"/user/info",Object.class);
}
}