1 搭建Eureka Server高可用集群
1.1 概述
- 在上面的章节，实现了单节点的Eureka Server的服务注册和服务发现功能。Eureka Client会定时连接到Eureka Server，获取注册表中的信息并缓存到本地。微服务在消费远程API的时候总是使用本地缓存中的数据。因此一般来说，即使Eureka Server出现宕机，也不会影响到服务之间的调用。但是如果Eureka Server宕机的时候，某些微服务也出现了不可用的情况，Eureka SClient中的缓存如果不被刷新，就可能影响到微服务的调用，甚至影响到整个应用系统的高可用。因此，在生产环境中，通常会部署一个高可用的Eureka Server集群。
- Eureka Server可用通过运行多个实例并相互注册的方式实现高可用部署，Eureka Server实例会彼此增量的同步信息，从而确保所有节点数据一致。事实上，节点之间相互注册时Eureka Server的默认行为。
1.2 搭建Eureka Server高可用集群
1.2.1 修改本机的host文件
- 由于个人计算机中进行测试很难模拟多主机的情况，Eureka配置server集群的时候需要修改host文件。在win10中host文件的路径是C:WindowsSystem32driversetchosts。
127.0.0.1 eureka7001.com
127.0.0.1 eureka7002.com
127.0.0.1 eureka7003.com
1.2.2 修改原先的Eureka Server
- application.yml：
server:
# 单机版的端口
# port: 9000
port: 7001 #端口
#配置Eureka Server
eureka:
instance:
# 主机地址名称
# hostname: localhost # 单机版的主机地址名称
hostname: eureka7001.com
client:
register-with-eureka: false # 是否将自己注册到注册中心
fetch-registry: false # 是否从Eureka中获取服务列表
service-url: # 配置暴露给Eureka Client的请求地址
# 单机版
# defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
defaultZone: http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
- 将原先的Eureka的模块名修改为eureka_service7001，其pom.xml如下：
<?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>org.sunxiaping</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<!-- 此处修改 -->
<artifactId>eureka_service7001</artifactId>
<dependencies>
<!-- 导入Eureka Server对应的坐标 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
</dependencies>
</project>
- 修改启动类：
package com.sunxiaping.eureka;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
/**
* @author 许威威
* @version 1.0
*/
@SpringBootApplication
@EnableEurekaServer //开启Eureka Server
//将启动类名称由EurekaApplication修改为Eureka7001Application
public class Eureka7001Application {
public static void main(String[] args) {
SpringApplication.run(Eureka7001Application.class, args);
}
}
- 修改总工程的pom.xml：
<?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>
<packaging>pom</packaging>
<modules>
<module>product_service</module>
<module>spring_cloud_common</module>
<module>order_service</module>
<!-- 此处修改 -->
<module>eureka_service7001</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
</parent>
<groupId>org.sunxiaping</groupId>
<artifactId>spring_cloud_demo</artifactId>
<version>1.0</version>
<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>
<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>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.4</version>
<scope>provided</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Greenwich.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
<repository>
<id>spring-releases</id>
<name>Spring Releases</name>
<url>http://repo.spring.io/libs-release-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
<build>
<finalName>spring_cloud_demo</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<configuration>
<delimiters>
<delimit>$</delimit>
</delimiters>
</configuration>
</plugin>
</plugins>
</build>
</project>
1.2.3 搭建eureka_service7002模块
- pom.xml（复制eureka_service7001模块的pom.xml）：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>spring_cloud_demo</artifactId>
<groupId>org.sunxiaping</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>eureka_service7002</artifactId>
<dependencies>
<!-- 导入Eureka Server对应的坐标 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
</dependencies>
</project>
- application.yml：
server:
# 单机版的端口
# port: 9000
port: 7002 #端口
#配置Eureka Server
eureka:
instance:
# 主机地址名称
# hostname: localhost # 单机版的主机地址名称
hostname: eureka7002.com
client:
register-with-eureka: false # 是否将自己注册到注册中心
fetch-registry: false # 是否从Eureka中获取服务列表
service-url: # 配置暴露给Eureka Client的请求地址
# 单机版
# defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7003.com:7003/eureka/
- 总工程的pom.xml
<?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>
<packaging>pom</packaging>
<modules>
<module>product_service</module>
<module>spring_cloud_common</module>
<module>order_service</module>
<!-- 此处修改 -->
<module>eureka_service7001</module>
<module>eureka_service7002</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
</parent>
<groupId>org.sunxiaping</groupId>
<artifactId>spring_cloud_demo</artifactId>
<version>1.0</version>
<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>
<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>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.4</version>
<scope>provided</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Greenwich.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
<repository>
<id>spring-releases</id>
<name>Spring Releases</name>
<url>http://repo.spring.io/libs-release-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
<build>
<finalName>spring_cloud_demo</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<configuration>
<delimiters>
<delimit>$</delimit>
</delimiters>
</configuration>
</plugin>
</plugins>
</build>
</project>
- 启动类：
package com.sunxiaping.eureka;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
/**
* @author 许威威
* @version 1.0
*/
@SpringBootApplication
@EnableEurekaServer //开启Eureka Server
public class Eureka7002Application {
public static void main(String[] args) {
SpringApplication.run(Eureka7002Application.class, args);
}
}
1.2.4 搭建eureka_service7003模块
- pom.xml（复制eureka_service7001模块的pom.xml）：
<?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>org.sunxiaping</groupId>
<version>1.0</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>eureka_service7003</artifactId>
<dependencies>
<!-- 导入Eureka Server对应的坐标 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
</dependencies>
</project>
- application.yml：
server:
# 单机版的端口
# port: 9000
port: 7003 #端口
#配置Eureka Server
eureka:
instance:
# 主机地址名称
# hostname: localhost # 单机版的主机地址名称
hostname: eureka7003.com
client:
register-with-eureka: false # 是否将自己注册到注册中心
fetch-registry: false # 是否从Eureka中获取服务列表
service-url: # 配置暴露给Eureka Client的请求地址
# 单机版
# defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/
- 总工程的pom.xml：
<?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>
<packaging>pom</packaging>
<modules>
<module>product_service</module>
<module>spring_cloud_common</module>
<module>order_service</module>
<!-- 此处修改 -->
<module>eureka_service7001</module>
<module>eureka_service7002</module>
<module>eureka_service7003</module>
</modules>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
</parent>
<groupId>org.sunxiaping</groupId>
<artifactId>spring_cloud_demo</artifactId>
<version>1.0</version>
<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>
<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>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.4</version>
<scope>provided</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Greenwich.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
<repository>
<id>spring-releases</id>
<name>Spring Releases</name>
<url>http://repo.spring.io/libs-release-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>http://repo.spring.io/libs-snapshot-local</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>http://repo.spring.io/libs-milestone-local</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
<build>
<finalName>spring_cloud_demo</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<configuration>
<delimiters>
<delimit>$</delimit>
</delimiters>
</configuration>
</plugin>
</plugins>
</build>
</project>
- 启动类：
package com.sunxiaping.eureka;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
/**
* @author 许威威
* @version 1.0
*/
@SpringBootApplication
@EnableEurekaServer //开启Eureka Server
public class Eureka7003Application {
public static void main(String[] args) {
SpringApplication.run(Eureka7003Application.class, args);
}
}
1.2.5 修改商品微服务的yml，将注册地址改为Eureka Server集群地址
- application.yml：
server:
port: 9001 # 微服务的端口号
spring:
application:
name: service-product # 微服务的名称
datasource:
url: jdbc:mysql://192.168.237.100:3306/test?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
driver-class-name: com.mysql.cj.jdbc.Driver
username: root
password: 123456
jpa:
generate-ddl: true
show-sql: true
open-in-view: true
database: mysql
# 配置 eureka
eureka:
instance:
# 主机名称:服务名称修改，其实就是向eureka server中注册的实例id
instance-id: service-product:9001
# 显示IP信息
prefer-ip-address: true
client:
service-url: # 此处修改为 Eureka Server的集群地址
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
# 微服务info内容详细信息
info:
app.name: xxx
company.name: xxx
build.artifactId: $project.artifactId$
build.version: $project.version$
2 Eureka中的常见问题
2.1 服务注册慢
- 默认情况下，服务注册到Eureka Server的过程较慢。
- 服务的注册设计到心跳，默认心跳的间隔为30s。在实例、服务器和客户端都在本地缓存中具有相同的元数据之前，服务不可用于客户端发现。可用通过配置
eureka.instance.lease-renewal-interval-in-seconds（心跳续约间隔）来加快客户端连接到其他服务的过程。在生产中，最好使用默认值，因为在服务器内部有一些计算，它们对续约做出假设。
2.2 服务节点剔除问题
- 默认情况下，由于Eureka Server剔除失效服务间隔时间为90s且存在自我保护机制。所以不能有效而迅速的剔除失效节点，这对于开发或测试会造成困扰。解决方案如下：
- 对于Eureka Client：配置开启健康检查，并设置续约时间。
# 配置 eureka
eureka:
instance:
# 主机名称:服务名称修改，其实就是向eureka server中注册的实例id
instance-id: service-product:9001
# 显示IP信息
prefer-ip-address: true
lease-renewal-interval-in-seconds: 5 # 发送心跳续约间隔（默认30秒）
lease-expiration-duration-in-seconds: 10 # Eureka Client发送心跳给Eureka Server端后，续约到期时间（默认90秒）
client:
healthcheck:
enable: true #开启健康检查(依赖spring-boot-actuator)
service-url: # 此处修改为 Eureka Server的集群地址
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
- 对于Eureka Server：配置关闭自我保护，设置剔除无效节点的时间间隔。
#配置Eureka Server
eureka:
instance:
# 主机地址名称
# hostname: localhost # 单机版的主机地址名称
hostname: eureka7001.com
client:
register-with-eureka: false # 是否将自己注册到注册中心
fetch-registry: false # 是否从Eureka中获取服务列表
service-url: # 配置暴露给Eureka Client的请求地址
# 单机版
# defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
defaultZone: http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
server:
enable-self-preservation: false # 关闭自我保护
eviction-interval-timer-in-ms: 4000 #剔除时间间隔，单位：毫秒
3 Eureka的源码解析
3.1 Eureka服务注册核心源码解析
3.1.1 @EnableEurekaServer注解的作用
- 通过@EnableEurekaServer注解激活EurekaServer。
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({EurekaServerMarkerConfiguration.class})
public @interface EnableEurekaServer {
}
- @EnableEurekaServer注解向Spring容器中导入了一个EurekaServerMarkerConfiguration组件，EurekaServerMarkerConfiguration组件的源码如下：
@Configuration
public class EurekaServerMarkerConfiguration {
//向容器中导入了Marker组件，Marker组件是实例化核心配置类的前提条件
@Bean
public Marker eurekaServerMarkerBean() {
return new Marker();
}
class Marker {
}
}
3.1.2 自动装载核心配置类
- SpringCloud对EurekaServer的封装使得发布EurekaServer变得无比简单，根据自动状态的原则可以在spring-cloud-netflix-eureka-server-2.1.0.RELEASE.jar下找到spring.factories文件。
- 根据SpringBoot自动配置原理，即SpringBoot启动的时候会加载所有jar包下的META-INF下的spring.factories文件中的org.springframework.boot.autoconfigure.EnableAutoConfiguration对应的自动配置类。所以，SpringBoot启动的时候会加载EurekaServerAutoConfiguration（EurekaServer的自动配置类），其源码如下：
@Configuration
@Import(EurekaServerInitializerConfiguration.class)
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)
@EnableConfigurationProperties({ EurekaDashboardProperties.class,InstanceRegistryProperties.class })
@PropertySource("classpath:/eureka/server.properties")
public class EurekaServerAutoConfiguration extends WebMvcConfigurerAdapter {
//其他略
}
-
接下来解释EurekaServerAutoConfiguration（Eureka Server自动配置类）的作用：
-
1️⃣EurekaServerAutoConfiguration（Eureka Server自动配置类）生效的前提是容器中存在EurekaServerMarkerConfiguration.Marker组件（可以从
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)这段代码看出），而@EnableEurekaServer注解的作用就是向容器中添加EurekaServerMarkerConfiguration.Marker组件，所以如果不在启动类中配置@EnableEurekaServer的话，那么EurekaServerAutoConfiguration（Eureka Server自动配置类）就不会起作用。 -
2️⃣从
@EnableConfigurationProperties({ EurekaDashboardProperties.class,InstanceRegistryProperties.class })代码中，我们知道EurekaServerAutoConfiguration（Eureka Server）向容器中导入了EurekaDashboardProperties和InstanceRegistryProperties两个组件。- EurekaDashboardProperties：配置EurekaServer管理台。
- InstanceRegistryProperties：配置期望续约数量和默认的通信数量。
-
3️⃣通过
@Import(EurekaServerInitializerConfiguration.class)引入启动类。
3.1.3 EurekaServerInitializerConfiguration
- EurekaServerInitializerConfiguration.java
@Configuration
public class EurekaServerInitializerConfiguration
implements ServletContextAware, SmartLifecycle, Ordered {
private static final Log log = LogFactory.getLog(EurekaServerInitializerConfiguration.class);
@Autowired
private EurekaServerConfig eurekaServerConfig;
private ServletContext servletContext;
@Autowired
private ApplicationContext applicationContext;
@Autowired
private EurekaServerBootstrap eurekaServerBootstrap;
private boolean running;
private int order = 1;
@Override
public void setServletContext(ServletContext servletContext) {
this.servletContext = servletContext;
}
@Override
public void start() {
new Thread(new Runnable() {
@Override
public void run() {
try {
//TODO: is this class even needed now?
eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);
log.info("Started Eureka Server");
publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));
EurekaServerInitializerConfiguration.this.running = true;
publish(new EurekaServerStartedEvent(getEurekaServerConfig()));
}
catch (Exception ex) {
// Help!
log.error("Could not initialize Eureka servlet context", ex);
}
}
}).start();
}
private EurekaServerConfig getEurekaServerConfig() {
return this.eurekaServerConfig;
}
private void publish(ApplicationEvent event) {
this.applicationContext.publishEvent(event);
}
@Override
public void stop() {
this.running = false;
eurekaServerBootstrap.contextDestroyed(this.servletContext);
}
@Override
public boolean isRunning() {
return this.running;
}
@Override
public int getPhase() {
return 0;
}
@Override
public boolean isAutoStartup() {
return true;
}
@Override
public void stop(Runnable callback) {
callback.run();
}
@Override
public int getOrder() {
return this.order;
}
}
- 从源码中，可以看出EurekaServerInitializerConfiguration实现了SmartLifecycle，意味着Spring容器启动时会指定start()方法。加载所有的EurekaServer的配置。
3.1.4 EurekaServerAutoConfiguration
- EurekaServerAutoConfiguration的部分源码如下：
@Configuration
@Import(EurekaServerInitializerConfiguration.class)
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)
@EnableConfigurationProperties({ EurekaDashboardProperties.class,
InstanceRegistryProperties.class })
@PropertySource("classpath:/eureka/server.properties")
public class EurekaServerAutoConfiguration extends WebMvcConfigurerAdapter {
//实例化了Eureka Server的管控台Controller类EurekaController
@Bean
@ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true)
public EurekaController eurekaController() {
return new EurekaController(this.applicationInfoManager);
}
//实例化EurekaServerBootstrap类
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager,
this.eurekaClientConfig, this.eurekaServerConfig, registry,
serverContext);
}
//实例化jersey相关配置类
@Bean
public FilterRegistrationBean jerseyFilterRegistration(
javax.ws.rs.core.Application eurekaJerseyApp) {
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(new ServletContainer(eurekaJerseyApp));
bean.setOrder(Ordered.LOWEST_PRECEDENCE);
bean.setUrlPatterns(
Collections.singletonList(EurekaConstants.DEFAULT_PREFIX + "/*"));
return bean;
}
//jerseyApplication方法，在容器中存放了一个jerseyApplication对象，
//jerseyApplication方法和Spring源码扫描@Component逻辑类似，扫描@Path和@Provider标签，然后封装成BeanDefinition，
//封装到APPlication里面的Set容器。然后Filter过滤器来过滤URL进行映射到对象的Controller
@Bean
public javax.ws.rs.core.Application jerseyApplication(Environment environment,
ResourceLoader resourceLoader) {
ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(
false, environment);
// Filter to include only classes that have a particular annotation.
//
provider.addIncludeFilter(new AnnotationTypeFilter(Path.class));
provider.addIncludeFilter(new AnnotationTypeFilter(Provider.class));
// Find classes in Eureka packages (or subpackages)
//
Set<Class<?>> classes = new HashSet<>();
for (String basePackage : EUREKA_PACKAGES) {
Set<BeanDefinition> beans = provider.findCandidateComponents(basePackage);
for (BeanDefinition bd : beans) {
Class<?> cls = ClassUtils.resolveClassName(bd.getBeanClassName(),
resourceLoader.getClassLoader());
classes.add(cls);
}
}
}
3.1.5 暴露的服务端接口
- 由于集成了Jersey，我们可以找到Eureka Server的依赖包中的
eureka-core-1.9.8.jar，可以看到一些列的XxxResource。
- 上面的这些类都是通过Jersey发布的供客户端调用的服务接口。
3.1.6 服务端接收客户端的注册
- 在ApplicationResource的addInstance()方法中可以看到
this.registry.register(info, "true".equals(isReplication));。
@Produces({"application/xml", "application/json"})
public class ApplicationResource {
@POST
@Consumes({"application/json", "application/xml"})
public Response addInstance(InstanceInfo info, @HeaderParam("x-netflix-discovery-replication") String isReplication) {
logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
if (this.isBlank(info.getId())) {
return Response.status(400).entity("Missing instanceId").build();
} else if (this.isBlank(info.getHostName())) {
return Response.status(400).entity("Missing hostname").build();
} else if (this.isBlank(info.getIPAddr())) {
return Response.status(400).entity("Missing ip address").build();
} else if (this.isBlank(info.getAppName())) {
return Response.status(400).entity("Missing appName").build();
} else if (!this.appName.equals(info.getAppName())) {
return Response.status(400).entity("Mismatched appName, expecting " + this.appName + " but was " + info.getAppName()).build();
} else if (info.getDataCenterInfo() == null) {
return Response.status(400).entity("Missing dataCenterInfo").build();
} else if (info.getDataCenterInfo().getName() == null) {
return Response.status(400).entity("Missing dataCenterInfo Name").build();
} else {
DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
if (dataCenterInfo instanceof UniqueIdentifier) {
String dataCenterInfoId = ((UniqueIdentifier)dataCenterInfo).getId();
if (this.isBlank(dataCenterInfoId)) {
boolean experimental = "true".equalsIgnoreCase(this.serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
if (experimental) {
String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
return Response.status(400).entity(entity).build();
}
if (dataCenterInfo instanceof AmazonInfo) {
AmazonInfo amazonInfo = (AmazonInfo)dataCenterInfo;
String effectiveId = amazonInfo.get(MetaDataKey.instanceId);
if (effectiveId == null) {
amazonInfo.getMetadata().put(MetaDataKey.instanceId.getName(), info.getId());
}
} else {
logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
}
}
}
this.registry.register(info, "true".equals(isReplication));
return Response.status(204).build();
}
}
}
- register()方法的有关源码如下：
@Singleton
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
@Override
public void register(final InstanceInfo info, final boolean isReplication) {
//默认有效时长为90秒
int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
leaseDuration = info.getLeaseInfo().getDurationInSecs();
}
//注册实例
super.register(info, leaseDuration, isReplication);
//同步到其他的Eureka Server服务
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
//其他略
}
- 继续找到父类的register方法可以看到整个注册过程：
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
//线程安全的Map，存放所有注册的实例对象
private final ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>> registry
= new ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>>();
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
Map<String, Lease<InstanceInfo>> gMap = registry.get(registrant.getAppName());
REGISTER.increment(isReplication);
//如果第一个实例注册会给registry put进去一个空的
if (gMap == null) {
final ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap<String, Lease<InstanceInfo>>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
// 根据注册的实例对象id，获取已经存在的Lease
Lease<InstanceInfo> existingLease = gMap.get(registrant.getId());
// Retain the last dirty timestamp without overwriting it, if there is already a lease
if (existingLease != null && (existingLease.getHolder() != null)) {
Long existingLastDirtyTimestamp = existingLease.getHolder().getLastDirtyTimestamp();
Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();
logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
// this is a > instead of a >= because if the timestamps are equal, we still take the remote transmitted
// InstanceInfo instead of the server local copy.
if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) {
logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater" +
" than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant");
registrant = existingLease.getHolder();
}
} else {
// The lease does not exist and hence it is a new registration
synchronized (lock) {
if (this.expectedNumberOfClientsSendingRenews > 0) {
// Since the client wants to register it, increase the number of clients sending renews
this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews + 1;
updateRenewsPerMinThreshold();
}
}
logger.debug("No previous lease information found; it is new registration");
}
Lease<InstanceInfo> lease = new Lease<InstanceInfo>(registrant, leaseDuration);
if (existingLease != null) {
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
//将lease存入gMap
gMap.put(registrant.getId(), lease);
synchronized (recentRegisteredQueue) {
recentRegisteredQueue.add(new Pair<Long, String>(
System.currentTimeMillis(),
registrant.getAppName() + "(" + registrant.getId() + ")"));
}
// This is where the initial state transfer of overridden status happens
if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) {
logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the "
+ "overrides", registrant.getOverriddenStatus(), registrant.getId());
if (!overriddenInstanceStatusMap.containsKey(registrant.getId())) {
logger.info("Not found overridden id {} and hence adding it", registrant.getId());
overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
}
}
InstanceStatus overriddenStatusFromMap = overriddenInstanceStatusMap.get(registrant.getId());
if (overriddenStatusFromMap != null) {
logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
registrant.setOverriddenStatus(overriddenStatusFromMap);
}
// Set the status based on the overridden status rules
InstanceStatus overriddenInstanceStatus = getOverriddenInstanceStatus(registrant, existingLease, isReplication);
registrant.setStatusWithoutDirty(overriddenInstanceStatus);
// If the lease is registered with UP status, set lease service up timestamp
if (InstanceStatus.UP.equals(registrant.getStatus())) {
lease.serviceUp();
}
registrant.setActionType(ActionType.ADDED);
recentlyChangedQueue.add(new RecentlyChangedItem(lease));
registrant.setLastUpdatedTimestamp();
invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
logger.info("Registered instance {}/{} with status {} (replication={})",
registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);
} finally {
read.unlock();
}
}
//其他略
}
3.1.7 服务端接收客户端的续约
- 在InstanceResource的renewLease方法中完成客户端的心跳（续约）处理，其中最关键的方法就是
registry.renew(app.getName(), id, isFromReplicaNode);。
@Produces({"application/xml", "application/json"})
public class InstanceResource {
@PUT
public Response renewLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
@QueryParam("overriddenstatus") String overriddenStatus,
@QueryParam("status") String status,
@QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
boolean isFromReplicaNode = "true".equals(isReplication);
//服务端接收客户端的续约
boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);
// Not found in the registry, immediately ask for a register
if (!isSuccess) {
logger.warn("Not Found (Renew): {} - {}", app.getName(), id);
return Response.status(Status.NOT_FOUND).build();
}
// Check if we need to sync based on dirty time stamp, the client
// instance might have changed some value
Response response;
if (lastDirtyTimestamp != null && serverConfig.shouldSyncWhenTimestampDiffers()) {
response = this.validateDirtyTimestamp(Long.valueOf(lastDirtyTimestamp), isFromReplicaNode);
// Store the overridden status since the validation found out the node that replicates wins
if (response.getStatus() == Response.Status.NOT_FOUND.getStatusCode()
&& (overriddenStatus != null)
&& !(InstanceStatus.UNKNOWN.name().equals(overriddenStatus))
&& isFromReplicaNode) {
registry.storeOverriddenStatusIfRequired(app.getAppName(), id, InstanceStatus.valueOf(overriddenStatus));
}
} else {
response = Response.ok().build();
}
logger.debug("Found (Renew): {} - {}; reply status={}", app.getName(), id, response.getStatus());
return response;
}
}
- renew()方法的源码如下：
@Singleton
public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
public boolean renew(final String appName, final String id, final boolean isReplication) {
//客户端续约
if (super.renew(appName, id, isReplication)) {
//同步到其他的Eureka Server服务
replicateToPeers(Action.Heartbeat, appName, id, null, null, isReplication);
return true;
}
return false;
}
//其他略
}
- 继续找到父类的renew方法可以看到整个续约过程：
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public boolean renew(String appName, String id, boolean isReplication) {
RENEW.increment(isReplication);
Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
Lease<InstanceInfo> leaseToRenew = null;
if (gMap != null) {
//从Map中根据id获取实例对象的Lease对象
leaseToRenew = gMap.get(id);
}
if (leaseToRenew == null) {
RENEW_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: lease doesn't exist, registering resource: {} - {}", appName, id);
return false;
} else {
//获取实例对象
InstanceInfo instanceInfo = leaseToRenew.getHolder();
if (instanceInfo != null) {
// touchASGCache(instanceInfo.getASGName());
InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(
instanceInfo, leaseToRenew, isReplication);
if (overriddenInstanceStatus == InstanceStatus.UNKNOWN) {
logger.info("Instance status UNKNOWN possibly due to deleted override for instance {}"
+ "; re-register required", instanceInfo.getId());
RENEW_NOT_FOUND.increment(isReplication);
return false;
}
if (!instanceInfo.getStatus().equals(overriddenInstanceStatus)) {
logger.info(
"The instance status {} is different from overridden instance status {} for instance {}. "
+ "Hence setting the status to overridden status", instanceInfo.getStatus().name(),
instanceInfo.getOverriddenStatus().name(),
instanceInfo.getId());
//设置实例状态
instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus);
}
}
//设置续约次数
renewsLastMin.increment();
leaseToRenew.renew();
return true;
}
}
}
3.1.8 服务剔除
- 在AbstractInstanceRegistry的postInit()方法中开启了一个每60秒调用一次EvictionTask的evict的定时器。
public abstract class AbstractInstanceRegistry implements InstanceRegistry {
public void evict(long additionalLeaseMs) {
logger.debug("Running the evict task");
if (!isLeaseExpirationEnabled()) {
logger.debug("DS: lease expiration is currently disabled.");
return;
}
// We collect first all expired items, to evict them in random order. For large eviction sets,
// if we do not that, we might wipe out whole apps before self preservation kicks in. By randomizing it,
// the impact should be evenly distributed across all applications.
List<Lease<InstanceInfo>> expiredLeases = new ArrayList<>();
for (Entry<String, Map<String, Lease<InstanceInfo>>> groupEntry : registry.entrySet()) {
Map<String, Lease<InstanceInfo>> leaseMap = groupEntry.getValue();
if (leaseMap != null) {
for (Entry<String, Lease<InstanceInfo>> leaseEntry : leaseMap.entrySet()) {
Lease<InstanceInfo> lease = leaseEntry.getValue();
if (lease.isExpired(additionalLeaseMs) && lease.getHolder() != null) {
expiredLeases.add(lease);
}
}
}
}
// To compensate for GC pauses or drifting local time, we need to use current registry size as a base for
// triggering self-preservation. Without that we would wipe out full registry.
int registrySize = (int) getLocalRegistrySize();
int registrySizeThreshold = (int) (registrySize * serverConfig.getRenewalPercentThreshold());
int evictionLimit = registrySize - registrySizeThreshold;
int toEvict = Math.min(expiredLeases.size(), evictionLimit);
if (toEvict > 0) {
logger.info("Evicting {} items (expired={}, evictionLimit={})", toEvict, expiredLeases.size(), evictionLimit);
Random random = new Random(System.currentTimeMillis());
for (int i = 0; i < toEvict; i++) {
// Pick a random item (Knuth shuffle algorithm)
int next = i + random.nextInt(expiredLeases.size() - i);
Collections.swap(expiredLeases, i, next);
Lease<InstanceInfo> lease = expiredLeases.get(i);
String appName = lease.getHolder().getAppName();
String id = lease.getHolder().getId();
EXPIRED.increment();
logger.warn("DS: Registry: expired lease for {}/{}", appName, id);
internalCancel(appName, id, false);
}
}
}
//其他略
}
3.2 Eureka服务发现核心源码解析
3.2.1 自动装载
- 在消费者导入的坐标有spring-cloud-netflix-eureka-client-2.1.0.RELEASE.jar找到的spring.factories可以看到所有自动装载的配置类：
3.2.2 服务注册
- EurekaClientAutoConfiguration中注册了DiscoveryClient组件。
@Configuration
@EnableConfigurationProperties
@ConditionalOnClass(EurekaClientConfig.class)
@Import(DiscoveryClientOptionalArgsConfiguration.class)
@ConditionalOnBean(EurekaDiscoveryClientConfiguration.Marker.class)
@ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)
@AutoConfigureBefore({ NoopDiscoveryClientAutoConfiguration.class,
CommonsClientAutoConfiguration.class, ServiceRegistryAutoConfiguration.class })
@AutoConfigureAfter(name = {"org.springframework.cloud.autoconfigure.RefreshAutoConfiguration",
"org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration",
"org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration"})
public class EurekaClientAutoConfiguration {
@Bean
public DiscoveryClient discoveryClient(EurekaClient client, EurekaClientConfig clientConfig) {
return new EurekaDiscoveryClient(client, clientConfig);
}
//其他leukemia
}
- DiscoveryClient中有register方法，即服务注册方法：
@Singleton
public class DiscoveryClient implements EurekaClient {
//服务注册
boolean register() throws Throwable {
logger.info("DiscoveryClient_{}: registering service...", this.appPathIdentifier);
EurekaHttpResponse httpResponse;
try {
httpResponse = this.eurekaTransport.registrationClient.register(this.instanceInfo);
} catch (Exception var3) {
logger.warn("DiscoveryClient_{} - registration failed {}", new Object[]{this.appPathIdentifier, var3.getMessage(), var3});
throw var3;
}
if (logger.isInfoEnabled()) {
logger.info("DiscoveryClient_{} - registration status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
}
return httpResponse.getStatusCode() == Status.NO_CONTENT.getStatusCode();
}
//其他略
}
3.2.3 服务下架
- DiscoveryClient中有shutdown方法，即服务下架方法：
@Singleton
public class DiscoveryClient implements EurekaClient {
@PreDestroy
public synchronized void shutdown() {
if (this.isShutdown.compareAndSet(false, true)) {
logger.info("Shutting down DiscoveryClient ...");
if (this.statusChangeListener != null && this.applicationInfoManager != null) {
this.applicationInfoManager.unregisterStatusChangeListener(this.statusChangeListener.getId());
}
this.cancelScheduledTasks();
if (this.applicationInfoManager != null && this.clientConfig.shouldRegisterWithEureka() && this.clientConfig.shouldUnregisterOnShutdown()) {
this.applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
this.unregister();
}
if (this.eurekaTransport != null) {
this.eurekaTransport.shutdown();
}
this.heartbeatStalenessMonitor.shutdown();
this.registryStalenessMonitor.shutdown();
logger.info("Completed shut down of DiscoveryClient");
}
}
//其他略
}
3.2.4 心跳续约
- DiscoveryClient的HeartbeatThread中定义了续约的操作：
@Singleton
public class DiscoveryClient implements EurekaClient {
private class HeartbeatThread implements Runnable {
private HeartbeatThread() {
}
public void run() {
if (DiscoveryClient.this.renew()) {
DiscoveryClient.this.lastSuccessfulHeartbeatTimestamp = System.currentTimeMillis();
}
}
}
boolean renew() {
try {
EurekaHttpResponse<InstanceInfo> httpResponse = this.eurekaTransport.registrationClient.sendHeartBeat(this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceStatus)null);
logger.debug("DiscoveryClient_{} - Heartbeat status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {
this.REREGISTER_COUNTER.increment();
logger.info("DiscoveryClient_{} - Re-registering apps/{}", this.appPathIdentifier, this.instanceInfo.getAppName());
long timestamp = this.instanceInfo.setIsDirtyWithTime();
boolean success = this.register();
if (success) {
this.instanceInfo.unsetIsDirty(timestamp);
}
return success;
} else {
return httpResponse.getStatusCode() == Status.OK.getStatusCode();
}
} catch (Throwable var5) {
logger.error("DiscoveryClient_{} - was unable to send heartbeat!", this.appPathIdentifier, var5);
return false;
}
}
//其他略
}