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Spring Cloud源码分析之Eureka第八章:服务注册名称

来源:互联网 作者:佚名 时间:2022-07-19 11:25
欢迎访问我的GitHub 这里分类和汇总了欣宸的全部原创(含配套源码):https://github.com/zq2599/blog_demos 关于服务注册名称 服务注册名称,是指Eureka client注册到Eureka server时,用于标记自己身份

欢迎访问我的GitHub

这里分类和汇总了欣宸的全部原创(含配套源码):https://github.com/zq2599/blog_demos

关于服务注册名称

  • 服务注册名称,是指Eureka client注册到Eureka server时,用于标记自己身份的标志,举例说明,以下是个简单的Eureka client配置:

    server: port: 8082 spring: application: name: springcloud-deep-provider eureka: client: serviceUrl: defaultZone: http://localhost:8081/eureka/
  • 这样配置的应用,启动后如果在Eureka server注册成功,那么Eureka server的home页面信息如下,红框中就是注册名称:

image.png

  • 本文目标是通过分析Eureka client源码来找出这个名称是如何创建的;

关于源码版本

  • 本次分析的Spring Cloud版本为Edgware.RELEASE,对应的eureka-client版本为1.7.0;

从启动说起

  • 在spring-cloud-commons库的META-INF目录下有spring.factories文件,这是spring扩展规范的实现,这里面配置的类会被实例化,其中就包含了HostInfoEnvironmentPostProcessor这个类,如下图红框所示:

image.png

  • HostInfoEnvironmentPostProcessor实现了EnvironmentPostProcessor接口,来看看官方文档对EnvironmentPostProcessor的描述:

image.png

  • 上图红框中说明开发者可以自定义环境变量;
  • 上图绿框中说明EnvironmentPostProcessor的实现类必须在spring.factories文件中定义;
  • 因此HostInfoEnvironmentPostProcessor类的作用已经清楚了:自定义环境变量;

  • HostInfoEnvironmentPostProcessor源码如下:
public class HostInfoEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered { // Before ConfigFileApplicationListener private int order = ConfigFileApplicationListener.DEFAULT_ORDER - 1; @Override public int getOrder() { return this.order; } @Override public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) { InetUtils.HostInfo hostInfo = getFirstNonLoopbackHostInfo(environment); LinkedHashMap<String, Object> map = new LinkedHashMap<>(); map.put("spring.cloud.client.hostname", hostInfo.getHostname()); map.put("spring.cloud.client.ipAddress", hostInfo.getIpAddress()); MapPropertySource propertySource = new MapPropertySource( "springCloudClientHostInfo", map); environment.getPropertySources().addLast(propertySource); } private HostInfo getFirstNonLoopbackHostInfo(ConfigurableEnvironment environment) { InetUtilsProperties target = new InetUtilsProperties(); RelaxedDataBinder binder = new RelaxedDataBinder(target, InetUtilsProperties.PREFIX); binder.bind(new PropertySourcesPropertyValues(environment.getPropertySources())); try (InetUtils utils = new InetUtils(target)) { return utils.findFirstNonLoopbackHostInfo(); } } }
  • 上述代码有两处需要注意:
  • 第一,设置了两个环境变量:spring.cloud.client.hostname和spring.cloud.client.ipAddress;
  • 第二,getFirstNonLoopbackHostInfo方法返回的对象中,127.0.0.1这样的IP地址是会被过滤掉的,过滤逻辑很简单,源码在Inet4Address类的isLoopbackAddress方法:
public boolean isLoopbackAddress() { /* 127.x.x.x */ byte[] byteAddr = getAddress(); return byteAddr[0] == 127; }
  • 小结:HostInfoEnvironmentPostProcessor的作用是把本机的hostname和IP地址设置到环境变量中;

在配置类中保存服务名称

  • 接下来看看配置类EurekaClientAutoConfiguration,这里面主要是和Eureka相关的配置信息的数据和逻辑;
  • 请看方法eurekaInstanceConfigBean,该方法向Spring容器环境提供EurekaInstanceConfigBean实例,注意instance.setInstanceId(getDefaultInstanceId(propertyResolver)) 这一行:
@Bean @ConditionalOnMissingBean(value = EurekaInstanceConfig.class, search = SearchStrategy.CURRENT) public EurekaInstanceConfigBean eurekaInstanceConfigBean(InetUtils inetUtils, ManagementMetadataProvider managementMetadataProvider) throws MalformedURLException { PropertyResolver eurekaPropertyResolver = new RelaxedPropertyResolver(this.env, "eureka.instance."); String hostname = eurekaPropertyResolver.getProperty("hostname"); boolean preferIpAddress = Boolean.parseBoolean(eurekaPropertyResolver.getProperty("preferIpAddress")); boolean isSecurePortEnabled = Boolean.parseBoolean(eurekaPropertyResolver.getProperty("securePortEnabled")); String serverContextPath = propertyResolver.getProperty("server.contextPath", "/"); int serverPort = Integer.valueOf(propertyResolver.getProperty("server.port", propertyResolver.getProperty("port", "8080"))); Integer managementPort = propertyResolver.getProperty("management.port", Integer.class);// nullable. should be wrapped into optional String managementContextPath = propertyResolver.getProperty("management.contextPath");// nullable. should be wrapped into optional Integer jmxPort = propertyResolver.getProperty("com.sun.management.jmxremote.port", Integer.class);//nullable EurekaInstanceConfigBean instance = new EurekaInstanceConfigBean(inetUtils); instance.setNonSecurePort(serverPort); //服务自身的名称在此设置,保存到instance后,其他地方就可以使用了 instance.setInstanceId(getDefaultInstanceId(propertyResolver));
  • 顺藤摸瓜,展开方法getDefaultInstanceId:
public static String getDefaultInstanceId(PropertyResolver resolver) { RelaxedPropertyResolver relaxed = new RelaxedPropertyResolver(resolver); String vcapInstanceId = relaxed.getProperty("vcap.application.instance_id"); if (StringUtils.hasText(vcapInstanceId)) { return vcapInstanceId; } String hostname = relaxed.getProperty("spring.cloud.client.hostname"); String appName = relaxed.getProperty("spring.application.name"); String namePart = combineParts(hostname, SEPARATOR, appName); String indexPart = relaxed.getProperty("spring.application.instance_id", relaxed.getProperty("server.port")); return combineParts(namePart, SEPARATOR, indexPart); }
  • 如上述代码所示,真相大白,服务注册名称一共有三部分:hostname、应用名称、自定义实例ID,如果自定义实例ID没有配置就用监听端口代替;

  • 此时再来回顾之前在Eureka server的home页面上看到的服务注册名:localhost:springcloud-deep-provider:8082,果然与源码一致;
  • 源码读到此处,禁不住手痒,按照上面的逻辑,在应用的aplication.yml中增加配置项spring.application.instance_id,看看能否生效,改过的aplication.yml内容如下图所示,红框中是新增的自定义实例ID配置:

image.png

  • 重启应用,重新注册到Eureka server,此时再看home页面如下图红框,服务注册名称果然已经更新:

image.png

使用配置类中的服务名称

  • 现在我们知道了EurekaInstanceConfigBean实例的instanceId字段被设置为"hostname:应用名称:自定义实例ID",接下来看该字段如何被提交到Eureka server;

  • 在EurekaClientAutoConfiguration类中有个eurekaApplicationInfoManager方法,为spring容器提供了ApplicationInfoManager实例:
@Bean @ConditionalOnMissingBean(value = ApplicationInfoManager.class, search = SearchStrategy.CURRENT) public ApplicationInfoManager eurekaApplicationInfoManager( EurekaInstanceConfig config) { //config就是前面看到的EurekaInstanceConfigBean实例, //EurekaInstanceConfig是个接口,EurekaInstanceConfigBean是该接口的实现, //instanceInfo实例中已经保存了EurekaInstanceConfigBean的信息,也包括instanceId字段 InstanceInfo instanceInfo = new InstanceInfoFactory().create(config); //生成ApplicationInfoManager实例, //config和instanceInfo都被设置为ApplicationInfoManager实例的成员变量 return new ApplicationInfoManager(config, instanceInfo); }
  • 如上所示,spring容器中有了ApplicationInfoManager实例,就可以通过该实例获得服务注册名称;

  • Eureka client向Eureka server发起服务注册的操作是在DiscoveryClient类中进行的,该类的构造方法如下:

image.png

  • 如上图所示,红框中ApplicationInfoManager实例被注入,蓝框中表明DiscoveryClient的成员变量instanceInfo获得了InstanceInfo实例;

  • 具体的注册逻辑在DiscoveryClient的register方法中,可见成员变量instanceInfo被当作入参传入了注册逻辑的API:
/** * Register with the eureka service by making the appropriate REST call. */ boolean register() throws Throwable { logger.info(PREFIX + appPathIdentifier + ": registering service..."); EurekaHttpResponse<Void> httpResponse; try { //以成员变量instanceInfo作为入参进行注册 httpResponse = eurekaTransport.registrationClient.register(instanceInfo); } catch (Exception e) { logger.warn("{} - registration failed {}", PREFIX + appPathIdentifier, e.getMessage(), e); throw e; } if (logger.isInfoEnabled()) { logger.info("{} - registration status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode()); } return httpResponse.getStatusCode() == 204; }
  • 上述代码中的eurekaTransport.registrationClient.register(instanceInfo) 方法,经过层层调用,最终调用了AbstractJerseyEurekaHttpClient类的register方法,如下图所示:

image.png

  • 上图的红框表明,POST请求时InstanceInfo实例被作为请求参数提交到了Eureka server;

Wireshark抓包验证

  • 至此,代码分析已经结束了,最后我们用Wireshark抓包来验证之前的分析结果,在Eureka client所在电脑上用Wireshark2.6.3来分析注册请求:

image.png

  • 如上图所示,红框中就是注册请求,绿框中是请求包头的全部内容,也就是前面看到的InstanceInfo实例的内容,蓝框中的内容,就是服务注册名称的键值对,值就是Eureka server收到的注册名称;

  • 最后来小结一下,服务注册名称从诞生到提交至Eureka server的过程:
  • HostInfoEnvironmentPostProcessor将本机的hostname和IP地址设置到应用环境变量中;
  • 配置类EurekaClientAutoConfiguration中,创建一个EurekaInstanceConfigBean类型的bean,其instanceId字段就是即将上报到Eureka server的自身名称,instanceId字段的内容由hostname、应用名称、自定义实例ID拼接而成,其中自定义实例ID来自配置项"spring.application.instance_id",如果不存在就用服务监听端口代替;
  • ApplicationInfoManager类型的bean在创建时被注入EurekaInstanceConfigBean实例,用于创建ApplicationInfoManager的成员变量instanceInfo;
  • DiscoveryClient的构造方法中注入了ApplicationInfoManager,于是DiscoveryClient的成员变量instanceInfo就被赋值为ApplicationInfoManager的成员变量instanceInfo;
  • DiscoveryClient的register方法负责注册到Eureka server的逻辑,用到的参数就是成员变量instanceInfo;
  • 发起注册网络请求的操作最终由AbstractJerseyEurekaHttpClient类的register方法完成,POST的内容就是instanceInfo实例;

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