Eureka注册中心ip-Address参数详解

在Eureka中如果不指定任何的Ip参数的话，那么提供者注册到Eureka中，消费者进行消费的时候访问的Ip为部署Eureka服务器的Ip地址。

Eureka不加参数调用图

那么正常情况下，服务器A调用将会调到服务B的身上，而此时如果在服务B中加入了一下的参数。那么就变了

eureka.instance.prefer-ip-address=true
eureka.instance.ip-address=172.12.9.0

此时服务C和服务B是相同的服务，部署在不同的服务器中，Ip地址不同，那么此时调用的服务将会被Eureka转发到服务C中。

源代码详解

我们可以在EurekaClientAutoConfiguration类中找到eurekaInstanceConfigBean方法。发现他在程序启动的时候就会加载一些eureka的配置信息

@Bean
	@ConditionalOnMissingBean(value = EurekaInstanceConfig.class, search = SearchStrategy.CURRENT)
	public EurekaInstanceConfigBean eurekaInstanceConfigBean(InetUtils inetUtils,
															 ManagementMetadataProvider managementMetadataProvider, ConfigurableEnvironment env) throws MalformedURLException {
		PropertyResolver environmentPropertyResolver = new RelaxedPropertyResolver(env);
		PropertyResolver eurekaPropertyResolver = new RelaxedPropertyResolver(env, "eureka.instance.");
		String hostname = eurekaPropertyResolver.getProperty("hostname");

		boolean preferIpAddress = Boolean.parseBoolean(eurekaPropertyResolver.getProperty("preferIpAddress"));
		String ipAddress = eurekaPropertyResolver.getProperty("ipAddress");
		boolean isSecurePortEnabled = Boolean.parseBoolean(eurekaPropertyResolver.getProperty("securePortEnabled"));
		String serverContextPath = environmentPropertyResolver.getProperty("server.contextPath", "/");
		int serverPort = Integer.valueOf(environmentPropertyResolver.getProperty("server.port", environmentPropertyResolver.getProperty("port", "8080")));

		Integer managementPort = environmentPropertyResolver.getProperty("management.port", Integer.class);// nullable. should be wrapped into optional
		String managementContextPath = environmentPropertyResolver.getProperty("management.contextPath");// nullable. should be wrapped into optional
		Integer jmxPort = environmentPropertyResolver.getProperty("com.sun.management.jmxremote.port", Integer.class);//nullable
		EurekaInstanceConfigBean instance = new EurekaInstanceConfigBean(inetUtils);

		instance.setNonSecurePort(serverPort);
		instance.setInstanceId(getDefaultInstanceId(environmentPropertyResolver));
		instance.setPreferIpAddress(preferIpAddress);
		instance.setSecurePortEnabled(isSecurePortEnabled);
		if (StringUtils.hasText(ipAddress)) {
			instance.setIpAddress(ipAddress);
		}

		if(isSecurePortEnabled) {
			instance.setSecurePort(serverPort);
		}

		if (StringUtils.hasText(hostname)) {
			instance.setHostname(hostname);
		}
		String statusPageUrlPath = eurekaPropertyResolver.getProperty("statusPageUrlPath");
		String healthCheckUrlPath = eurekaPropertyResolver.getProperty("healthCheckUrlPath");

		if (StringUtils.hasText(statusPageUrlPath)) {
			instance.setStatusPageUrlPath(statusPageUrlPath);
		}
		if (StringUtils.hasText(healthCheckUrlPath)) {
			instance.setHealthCheckUrlPath(healthCheckUrlPath);
		}

		ManagementMetadata metadata = managementMetadataProvider.get(instance, serverPort,
				serverContextPath, managementContextPath, managementPort);

		if(metadata != null) {
			instance.setStatusPageUrl(metadata.getStatusPageUrl());
			instance.setHealthCheckUrl(metadata.getHealthCheckUrl());
			if(instance.isSecurePortEnabled()) {
				instance.setSecureHealthCheckUrl(metadata.getSecureHealthCheckUrl());
			}
			Map<String, String> metadataMap = instance.getMetadataMap();
			if (metadataMap.get("management.port") == null) {
				metadataMap.put("management.port", String.valueOf(metadata.getManagementPort()));
			}
		}

		setupJmxPort(instance, jmxPort);
		return instance;
	}

此时我们看到String ipAddress = eurekaPropertyResolver.getProperty("ipAddress");就是在这进行设置的，此时如果没有设置eureka.instance.ip-address参数的时候，那么此ipAddress就是本机的Ip。这是如何设置的呢？我们可以看到代码中有这么一句

EurekaInstanceConfigBean instance = new EurekaInstanceConfigBean(inetUtils);
instance.setNonSecurePort(serverPort);
instance.setInstanceId(getDefaultInstanceId(environmentPropertyResolver));
instance.setPreferIpAddress(preferIpAddress);
instance.setSecurePortEnabled(isSecurePortEnabled);
if (StringUtils.hasText(ipAddress)) {
	instance.setIpAddress(ipAddress);
}

EurekaInstanceConfigBean 先进行了初始化，我们进入EurekaInstanceConfigBean 的构造参数中看

	public EurekaInstanceConfigBean(InetUtils inetUtils) {
		this.inetUtils = inetUtils;
		this.hostInfo = this.inetUtils.findFirstNonLoopbackHostInfo();
		this.ipAddress = this.hostInfo.getIpAddress();
		this.hostname = this.hostInfo.getHostname();
	}

可以看到在这进行了初始化ipAddress参数，其中hostInfo是如何得到的就进行讲解了，其本质就是为了获取本机的真实IP。到这给Eureka注册中心的注册信息已经准备好了

然后在InstanceInfoReplicator中调用run方法进行将自己信息注册到远程的Eureka中。

此时就可以看到如果设置eureka.instance.prefer-ip-address为false时，那么注册到Eureka中的Ip地址就是本机的Ip地址。如果设置了true并且也设置了eureka.instance.ip-address那么就将此ip地址注册到Eureka中。那么调用的时候，发送的请求目的地就是此Ip地址。

不学无数——Eureka注册中心ip-Address参数详解