Eureka 的 Application Service 客户端的注册以及运行示例

        Eureka 服务器架起来了(关于架设步骤参考博客《 Linux 下 Eureka 服务器的部署》)，现在如何把我们要负载均衡的服务器(也就是从 Application Client 接收请求并返回一个响应的 Application Service)注册到 Eureka？本文以一个示例介绍 Eureka Application Service 客户端的 Eureka 生命周期(包括启动时的注册、侍服示例、关闭时的取消注册)情况，相信读完本文之后，读者可以对 Eureka 的 Application Service 角色有了一个进一步了解，而且完全可以把自己的服务加进 Eureka。
        1. Eureka 服务器启动
        本文 demo 要求 Eureka Server 已经部署好，并已经启动。关于架设步骤参考博客《 Linux 下 Eureka 服务器的部署》。
        Eureka 服务器启动以后，可以通过 http://serverIP:8080/eureka/ 或者 http://serverIP:8080/eureka/v2/apps/ 浏览已注册到 Eureka 的 Application Service。比如作者在开发环境 PC 访问服务器端的 http://serverIP:8080/eureka/v2/apps/，页面返回结果如下：

<applications>
	<versions__delta>1</versions__delta>
	<apps__hashcode>UP_1_</apps__hashcode>
	<application>
		<name>EUREKA</name>
		<instance>
			<hostName>localhost.localdomain</hostName>
			<app>EUREKA</app>
			<ipAddr>127.0.0.1</ipAddr>
			<status>UP</status>
			<overriddenstatus>UNKNOWN</overriddenstatus>
			<port enabled="true">8080</port>
			<securePort enabled="false">443</securePort>
			<countryId>1</countryId>
			<dataCenterInfo
				class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo">
				<name>MyOwn</name>
			</dataCenterInfo>
			<leaseInfo>
				<renewalIntervalInSecs>30</renewalIntervalInSecs>
				<durationInSecs>90</durationInSecs>
				<registrationTimestamp>1404789864122</registrationTimestamp>
				<lastRenewalTimestamp>1404798147096</lastRenewalTimestamp>
				<evictionTimestamp>0</evictionTimestamp>
				<serviceUpTimestamp>1404789841811</serviceUpTimestamp>
			</leaseInfo>
			<metadata class="java.util.Collections$EmptyMap" />
			<appGroupName>UNKNOWN</appGroupName>
			<homePageUrl>http://localhost.localdomain:8080/</homePageUrl>
			<statusPageUrl>http://localhost.localdomain:8080/Status</statusPageUrl>
			<healthCheckUrl>http://localhost.localdomain:8080/healthcheck</healthCheckUrl>
			<vipAddress>eureka.mydomain.net</vipAddress>
			<isCoordinatingDiscoveryServer>true</isCoordinatingDiscoveryServer>
			<lastUpdatedTimestamp>1404789864122</lastUpdatedTimestamp>
			<lastDirtyTimestamp>1404789841863</lastDirtyTimestamp>
			<actionType>ADDED</actionType>
		</instance>
	</application>
</applications>

        apps__hashcode 是 1，可以看出目前只有一个 Application Service 注册到了 Eureka Server，这个名为 Eureka 的 Application Service 只有一个实例，就是这台 Eureka Server 它自己 - localhost.localdomain。为何 Eureka Server 自己也是一个 Application Service 呢？这也是 Eureka 架构健壮性 feature 之一，Eureka Server 之间也会相互注册，而且还会将注册到自己的 Application Service 注册给其他 Eureka Server，避免了一台 Eureka Server 宕机所造成的区域性服务瘫痪。
        2. Application Service 配置文件的编写
        我们的负载均衡服务器就用官方提供 demo 里的 sampleservice 下的 sample-eureka-service.properties 即可，当然还要根据实际情况修正一下，比如把 eureka.name 改为我们自定义的 Application 名以区分开其他服务，把 eureka.port(本服务将会运行并侍服请求的端口)改为我们的 Service 服务器开放的侍服端口 1935，eureka.serviceUrl.default(默认情况下本服务将要注册到的 Eureka 服务器)： http://serverIP:8080/eureka/v2/：

###Eureka Client configuration for Sample Eureka Service


#Properties based configuration for eureka client. The properties specified here is mostly what the users
#need to change. All of these can be specified as a java system property with -D option (eg)-Deureka.region=us-east-1
#For additional tuning options refer <url to go here>




#Region where eureka is deployed -For AWS specify one of the AWS regions, for other datacenters specify a arbitrary string
#indicating the region.This is normally specified as a -D option (eg) -Deureka.region=us-east-1
eureka.region=default


#Name of the application to be identified by other services


eureka.name=sampleservice


#Virtual host name by which the clients identifies this service
eureka.vipAddress=sampleservice.mydomain.net


#The port where the service will be running and serving requests
eureka.port=1935


#For eureka clients running in eureka server, it needs to connect to servers in other zones
eureka.preferSameZone=false


#Change this if you want to use a DNS based lookup for determining other eureka servers. For example
#of specifying the DNS entries, check the eureka-client-test.properties, eureka-client-prod.properties
eureka.shouldUseDns=false


eureka.us-east-1.availabilityZones=default


eureka.serviceUrl.default=http://serverIP:8080/eureka/v2/

        3. 日志配置
        就用官方提供 demo 里的 sampleservice 下的 log4j.properties 即可，当然还要根据实际需要修正一下，比如给 com.defonds.wms.module.server 包的输出级别设置为 DEBUG(log4j.properties 追加 log4j.logger.com.defonds.wms.module.server=DEBUG)，以方便我们研发期跟踪调试。

log4j.rootCategory=INFO,stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %-5p %C:%L [%t] [%M] %m%n

        4. Application Service 启动时注册 Eureka
        我们希望每台负载均衡服务器在启动时就注册给 Eureka，以及时承担负载。注册代码如下所示：

    private static final DynamicPropertyFactory configInstance = com.netflix.config.DynamicPropertyFactory.getInstance();


    private static final Logger logger = LoggerFactory.getLogger(SampleEurekaService.class);


    public void registerWithEureka() {
        // Register with Eureka
        DiscoveryManager.getInstance().initComponent(
                new MyDataCenterInstanceConfig(),
                new DefaultEurekaClientConfig());
        ApplicationInfoManager.getInstance().setInstanceStatus(
                InstanceStatus.UP);
	}

        第一句加载本地配置文件，initComponent 句根据配置初始化这台 Eureka Application Service，并且注册到 Eureka Server，setInstanceStatus 句指示本台 Application Service 已启动，准备好侍服网络请求。
        5. Application Service 侍服网络请求
        Application Service 的 Eureka Server 初始化以及注册是异步的，需要一段时间，我们想要在确认初始化并注册成功之后，提供一个 Socket 服务，以供网络请求。demo 需要，这个服务是一次性的，只提供一次 Socket 侍服。侍服完一次请求后，本 Socket 服务就关闭，并将自己从 Eureka Server 取消注册。

        String vipAddress = configInstance.getStringProperty(
                "eureka.vipAddress", "sampleservice.mydomain.net").get();
        InstanceInfo nextServerInfo = null;
        while (nextServerInfo == null) {
            try {
                nextServerInfo = DiscoveryManager.getInstance()
                .getDiscoveryClient()
                .getNextServerFromEureka(vipAddress, false);
            } catch (Throwable e) {
                System.out
                .println("Waiting for service to register with eureka..");


                try {
                    Thread.sleep(10000);
                } catch (InterruptedException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }


            }
        }
        System.out.println("Service started and ready to process requests..");


        try {
            ServerSocket serverSocket = new ServerSocket(configInstance
                    .getIntProperty("eureka.port", 8010).get());
            final Socket s = serverSocket.accept();
            System.out
            .println("Client got connected..Processing request from the client");
            processRequest(s);


        } catch (IOException e) {
            e.printStackTrace();
        }

        Socket 侍服 processRequest 方法详细如下：

    private void processRequest(final Socket s) {
        try {
            BufferedReader rd = new BufferedReader(new InputStreamReader(
                    s.getInputStream()));
            String line = rd.readLine();
            if (line != null) {
                System.out.println("Received the request from the client.");
            }
            PrintStream out = new PrintStream(s.getOutputStream());
            System.out.println("Sending the response to the client...");


            out.println("Reponse at " + new Date());


        } catch (Throwable e) {
            System.err.println("Error processing requests");
        } finally {
            if (s != null) {
                try {
                    s.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }


    }	

        6. Application Service 关闭时取消注册
        就像 Spring 管理的对象，初始化、销毁都统一管理起来一样，我们希望本台 Application Service 实例在关闭时也能将自身占用的系统资源释放出来(比如任务列表的线程关闭)，而且取消掉 Eureka 服务器的注册。

    public void unRegisterWithEureka() {
        // Un register from eureka.
        DiscoveryManager.getInstance().shutdownComponent();
    }

        7. 运行 demo
        现在我们把完整的 Application Service 整理一下。

/*
 * Copyright 2012 Netflix, Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */


package com.netflix.eureka;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


import com.netflix.appinfo.ApplicationInfoManager;
import com.netflix.appinfo.InstanceInfo;
import com.netflix.appinfo.InstanceInfo.InstanceStatus;
import com.netflix.appinfo.MyDataCenterInstanceConfig;
import com.netflix.config.DynamicPropertyFactory;
import com.netflix.discovery.DefaultEurekaClientConfig;
import com.netflix.discovery.DiscoveryManager;


/**
 * Sample Eureka service that registers with Eureka to receive and process
 * requests.
 * 
 * <p>
 * This example just receives one request and exits once it receives the request
 * after processing it.
 * </p>
 * 
 * @author Karthik Ranganathan
 * 
 */
public class SampleEurekaService {
	
    private static final DynamicPropertyFactory configInstance = com.netflix.config.DynamicPropertyFactory
    .getInstance();


    private static final Logger logger = LoggerFactory
    .getLogger(SampleEurekaService.class);


    public void registerWithEureka() {
        // Register with Eureka
        DiscoveryManager.getInstance().initComponent(
                new MyDataCenterInstanceConfig(),
                new DefaultEurekaClientConfig());
        ApplicationInfoManager.getInstance().setInstanceStatus(
                InstanceStatus.UP);
        String vipAddress = configInstance.getStringProperty(
                "eureka.vipAddress", "sampleservice.mydomain.net").get();
        InstanceInfo nextServerInfo = null;
        while (nextServerInfo == null) {
            try {
                nextServerInfo = DiscoveryManager.getInstance()
                .getDiscoveryClient()
                .getNextServerFromEureka(vipAddress, false);
            } catch (Throwable e) {
                System.out
                .println("Waiting for service to register with eureka..");


                try {
                    Thread.sleep(10000);
                } catch (InterruptedException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }


            }
        }
        System.out.println("Service started and ready to process requests..");


        try {
            ServerSocket serverSocket = new ServerSocket(configInstance
                    .getIntProperty("eureka.port", 8010).get());
            final Socket s = serverSocket.accept();
            System.out
            .println("Client got connected..Processing request from the client");
            processRequest(s);


        } catch (IOException e) {
            e.printStackTrace();
        }
        this.unRegisterWithEureka();
        System.out.println("Shutting down server.Demo over.");


    }


    public void unRegisterWithEureka() {
        // Un register from eureka.
        DiscoveryManager.getInstance().shutdownComponent();
    }


    private void processRequest(final Socket s) {
        try {
            BufferedReader rd = new BufferedReader(new InputStreamReader(
                    s.getInputStream()));
            String line = rd.readLine();
            if (line != null) {
                System.out.println("Received the request from the client.");
            }
            PrintStream out = new PrintStream(s.getOutputStream());
            System.out.println("Sending the response to the client...");


            out.println("Reponse at " + new Date());


        } catch (Throwable e) {
            System.err.println("Error processing requests");
        } finally {
            if (s != null) {
                try {
                    s.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }


    }


    public static void main(String args[]) {
        SampleEurekaService sampleEurekaService = new SampleEurekaService();
        sampleEurekaService.registerWithEureka();
    }


}

        很明显我们的 SampleEurekaService 类需要很多依赖包，这些包都在 eureka-server-1.1.134.war 包里的 WEB-INF/lib 目录下，直接拷贝进我们 demo 的 CLASSPATH，不用一个个去找了，还避免了版本冲突所带来的不必要麻烦。eureka-client-1.1.134.jar 可以去 http://mvnrepository.com/artifact/com.netflix.eureka/eureka-client/1.1.134 下载，或者直接 maven 依赖导入：

<dependency>
	<groupId>com.netflix.eureka</groupId>
	<artifactId>eureka-client</artifactId>
	<version>1.1.134</version>
</dependency>

        类完成了、环境配置好了，接下来把第二、三步写好的 sample-eureka-service.properties、log4j.properties 也拷贝进 CLASSPATH，接下来就可以运行 demo 了。直接 run SampleEurekaService，发现报以下错误：
2014-07-07 17:01:50,141 WARN  com.netflix.config.sources.URLConfigurationSource:120 [main] [<init>] No URLs will be polled as dynamic configuration sources.
2014-07-07 17:01:50,144 INFO  com.netflix.config.sources.URLConfigurationSource:121 [main] [<init>] To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2014-07-07 17:01:50,178 INFO  com.netflix.config.DynamicPropertyFactory:281 [main] [getInstance] DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@6f25844f
2014-07-07 17:01:58,982 WARN  com.netflix.appinfo.PropertiesInstanceConfig:349 [main] [init] Cannot find the properties specified : eureka-client. This may be okay if there are other environment specific properties or the configuration is installed with a different mechanism.
2014-07-07 17:02:00,140 WARN  com.netflix.discovery.DefaultEurekaClientConfig:95 [main] [init] Cannot find the properties specified : eureka-client. This may be okay if there are other environment specific properties or the configuration is installed with a different mechanism.
2014-07-07 17:02:03,559 INFO  com.netflix.appinfo.providers.EurekaConfigBasedInstanceInfoProvider:79 [main] [get] Setting initial instance status as: STARTING
Exception in thread "main" java.lang.RuntimeException: Failed to initialize DiscoveryClient!
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:235)
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:169)
at com.netflix.discovery.DiscoveryManager.initComponent(DiscoveryManager.java:84)
at com.netflix.eureka.SampleEurekaService.registerWithEureka(SampleEurekaService.java:60)
at com.netflix.eureka.SampleEurekaService.main(SampleEurekaService.java:139)
Caused by: java.lang.IllegalArgumentException: DiscoveryClient: invalid serviceUrl specified!
at com.netflix.discovery.DiscoveryClient.getEurekaServiceUrlsFromConfig(DiscoveryClient.java:574)
at com.netflix.discovery.DiscoveryClient.getDiscoveryServiceUrls(DiscoveryClient.java:1180)
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:186)
... 4 more
        原来 Archaius 不认 sample-eureka-service.properties，没有把我们的配置成功加载。Archaius 的官方说，Archaius 在默认情况下(就是不指定 properties 文件的情况下)会在应用的 classpath 中寻找一个名为 config.properties 的文件并读取其内容作为配置属性。
        好吧，我们把 sample-eureka-service.properties 重命名为 config.properties，然后重新运行 SampleEurekaService。这次运行成功了，没有再报错。访问服务器端的 http://serverIP:8080/eureka/v2/apps/，显示如下页面信息：

<applications>
	<versions__delta>1</versions__delta>
	<apps__hashcode>UP_2_</apps__hashcode>
	<application>
		<name>SAMPLESERVICE</name>
		<instance>
			<hostName>defonds-win7</hostName>
			<app>SAMPLESERVICE</app>
			<ipAddr>172.21.40.134</ipAddr>
			<status>UP</status>
			<overriddenstatus>UNKNOWN</overriddenstatus>
			<port enabled="true">1935</port>
			<securePort enabled="false">443</securePort>
			<countryId>1</countryId>
			<dataCenterInfo
				class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo">
				<name>MyOwn</name>
			</dataCenterInfo>
			<leaseInfo>
				<renewalIntervalInSecs>30</renewalIntervalInSecs>
				<durationInSecs>90</durationInSecs>
				<registrationTimestamp>1404812488643</registrationTimestamp>
				<lastRenewalTimestamp>1404812609036</lastRenewalTimestamp>
				<evictionTimestamp>0</evictionTimestamp>
				<serviceUpTimestamp>1404812458545</serviceUpTimestamp>
			</leaseInfo>
			<metadata class="java.util.Collections$EmptyMap" />
			<appGroupName>UNKNOWN</appGroupName>
			<homePageUrl>http://defonds-win7:1935/</homePageUrl>
			<statusPageUrl>http://defonds-win7:1935/Status</statusPageUrl>
			<healthCheckUrl>http://defonds-win7:1935/healthcheck</healthCheckUrl>
			<vipAddress>sampleservice.mydomain.net</vipAddress>
			<isCoordinatingDiscoveryServer>false</isCoordinatingDiscoveryServer>
			<lastUpdatedTimestamp>1404812488643</lastUpdatedTimestamp>
			<lastDirtyTimestamp>1404812513644</lastDirtyTimestamp>
			<actionType>ADDED</actionType>
		</instance>
	</application>
	<application>
		<name>EUREKA</name>
		<instance>
			<hostName>localhost.localdomain</hostName>
			<app>EUREKA</app>
			<ipAddr>127.0.0.1</ipAddr>
			<status>UP</status>
			<overriddenstatus>UNKNOWN</overriddenstatus>
			<port enabled="true">8080</port>
			<securePort enabled="false">443</securePort>
			<countryId>1</countryId>
			<dataCenterInfo
				class="com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo">
				<name>MyOwn</name>
			</dataCenterInfo>
			<leaseInfo>
				<renewalIntervalInSecs>30</renewalIntervalInSecs>
				<durationInSecs>90</durationInSecs>
				<registrationTimestamp>1404812408111</registrationTimestamp>
				<lastRenewalTimestamp>1404812618042</lastRenewalTimestamp>
				<evictionTimestamp>0</evictionTimestamp>
				<serviceUpTimestamp>1404812385938</serviceUpTimestamp>
			</leaseInfo>
			<metadata class="java.util.Collections$EmptyMap" />
			<appGroupName>UNKNOWN</appGroupName>
			<homePageUrl>http://localhost.localdomain:8080/</homePageUrl>
			<statusPageUrl>http://localhost.localdomain:8080/Status
			</statusPageUrl>
			<healthCheckUrl>http://localhost.localdomain:8080/healthcheck
			</healthCheckUrl>
			<vipAddress>eureka.mydomain.net</vipAddress>
			<isCoordinatingDiscoveryServer>true</isCoordinatingDiscoveryServer>
			<lastUpdatedTimestamp>1404812408111</lastUpdatedTimestamp>
			<lastDirtyTimestamp>1404812385985</lastDirtyTimestamp>
			<actionType>ADDED</actionType>
		</instance>
	</application>
</applications>

        apps__hashcode 变成 2 了。可以看出多了一个 defonds-win7 名字的 instance，它的 IP 地址正是我运行 demo 的 PC 地址 172.21.40.134。访问 http://serverIP:8080/eureka/ 也可以看到该 instance：

        证明我们的 Application Service 已经成功注册到该台 Eureka Server。我们等待 Eureka Server 心跳访问该 Application Service，或者自己手工访问该 Application Service，以达成该服务器关闭条件，将其关闭，Application Service 成功取消注册。完整的 demo log 如下：
2014-07-08 10:06:54,124 INFO  com.netflix.config.sources.URLConfigurationSource:125 [main] [<init>] URLs to be used as dynamic configuration source: [file:/D:/javaprojects/test/bin/config.properties]
2014-07-08 10:06:54,259 INFO  com.netflix.config.DynamicPropertyFactory:281 [main] [getInstance] DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@2f774b9b
2014-07-08 10:08:32,464 WARN  com.netflix.appinfo.PropertiesInstanceConfig:349 [main] [init] Cannot find the properties specified : eureka-client. This may be okay if there are other environment specific properties or the configuration is installed with a different mechanism.
2014-07-08 10:08:35,592 WARN  com.netflix.discovery.DefaultEurekaClientConfig:95 [main] [init] Cannot find the properties specified : eureka-client. This may be okay if there are other environment specific properties or the configuration is installed with a different mechanism.
2014-07-08 10:08:45,835 INFO  com.netflix.appinfo.providers.EurekaConfigBasedInstanceInfoProvider:79 [main] [get] Setting initial instance status as: STARTING
2014-07-08 10:08:46,331 WARN  com.netflix.discovery.DiscoveryClient:1339 [main] [getZoneOffset] DISCOVERY: Could not pick a zone based on preferred zone settings. My zone - defaultZone, preferSameZone- false. Defaulting to defaultZone
2014-07-08 10:08:49,276 INFO  com.netflix.discovery.DiscoveryClient:646 [main] [fetchRegistry] Disable delta property : false
2014-07-08 10:08:49,277 INFO  com.netflix.discovery.DiscoveryClient:647 [main] [fetchRegistry] Single vip registry refresh property : null
2014-07-08 10:08:49,277 INFO  com.netflix.discovery.DiscoveryClient:648 [main] [fetchRegistry] Force full registry fetch : false
2014-07-08 10:08:49,277 INFO  com.netflix.discovery.DiscoveryClient:649 [main] [fetchRegistry] Application is null : false
2014-07-08 10:08:49,277 INFO  com.netflix.discovery.DiscoveryClient:650 [main] [fetchRegistry] Registered Applications size is zero : true
2014-07-08 10:08:49,278 INFO  com.netflix.discovery.DiscoveryClient:652 [main] [fetchRegistry] Application version is -1: true
2014-07-08 10:08:49,705 INFO  com.netflix.discovery.DiscoveryClient:992 [main] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/ with status code 200.
2014-07-08 10:08:49,706 INFO  com.netflix.discovery.DiscoveryClient:758 [main] [getAndStoreFullRegistry] Getting all instance registry info from the eureka server
2014-07-08 10:08:50,501 INFO  com.netflix.discovery.DiscoveryClient:765 [main] [getAndStoreFullRegistry] The response status is 200
2014-07-08 10:08:50,504 INFO  com.netflix.discovery.DiscoveryClient:1056 [main] [initScheduledTasks] Starting heartbeat executor: renew interval is: 30
2014-07-08 10:09:20,508 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-2] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:09:20,535 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-2] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_1_, is fetching remote regions? false 
2014-07-08 10:09:20,582 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-3] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 404.
2014-07-08 10:09:20,599 INFO  com.netflix.discovery.DiscoveryClient$HeartbeatThread:1415 [DiscoveryClient-3] [run] DiscoveryClient_SAMPLESERVICE/defonds-win7 - Re-registering apps/SAMPLESERVICE
2014-07-08 10:09:20,600 INFO  com.netflix.discovery.DiscoveryClient:509 [DiscoveryClient-3] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7: registering service...
2014-07-08 10:09:20,648 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-3] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE with status code 204.
2014-07-08 10:09:20,649 INFO  com.netflix.discovery.DiscoveryClient:514 [DiscoveryClient-3] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7 - registration status: 204
Waiting for service to register with eureka..
2014-07-08 10:09:30,513 INFO  com.netflix.discovery.DiscoveryClient$InstanceInfoReplicator:1476 [DiscoveryClient-2] [run] DiscoveryClient_SAMPLESERVICE/defonds-win7 - retransmit instance info with status UP
2014-07-08 10:09:30,514 INFO  com.netflix.discovery.DiscoveryClient:509 [DiscoveryClient-2] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7: registering service...
2014-07-08 10:09:30,561 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-2] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE with status code 204.
2014-07-08 10:09:30,562 INFO  com.netflix.discovery.DiscoveryClient:514 [DiscoveryClient-2] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7 - registration status: 204
2014-07-08 10:09:50,540 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:09:50,543 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-1] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:09:50,654 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 404.
2014-07-08 10:09:50,654 INFO  com.netflix.discovery.DiscoveryClient$HeartbeatThread:1415 [DiscoveryClient-1] [run] DiscoveryClient_SAMPLESERVICE/defonds-win7 - Re-registering apps/SAMPLESERVICE
2014-07-08 10:09:50,654 INFO  com.netflix.discovery.DiscoveryClient:509 [DiscoveryClient-1] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7: registering service...
2014-07-08 10:09:50,674 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE with status code 204.
2014-07-08 10:09:50,674 INFO  com.netflix.discovery.DiscoveryClient:514 [DiscoveryClient-1] [register] DiscoveryClient_SAMPLESERVICE/defonds-win7 - registration status: 204
Service started and ready to process requests..
2014-07-08 10:10:20,548 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-2] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:10:20,551 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-2] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:10:20,678 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
2014-07-08 10:10:50,556 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:10:50,559 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-1] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:10:50,681 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-0] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
2014-07-08 10:11:20,563 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:11:20,566 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-1] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:11:20,684 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
2014-07-08 10:11:50,570 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-2] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:11:50,573 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-2] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:11:50,687 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-1] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
2014-07-08 10:12:20,579 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-0] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/delta with status code 200.
2014-07-08 10:12:20,582 INFO  com.netflix.discovery.DiscoveryClient$CacheRefreshThread:1542 [DiscoveryClient-0] [run] Completed cache refresh task for discovery. All Apps hash code is Local region apps hashcode: UP_2_, is fetching remote regions? false 
2014-07-08 10:12:20,691 INFO  com.netflix.discovery.DiscoveryClient:992 [DiscoveryClient-0] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
Client got connected..Processing request from the client
Received the request from the client.
Sending the response to the client...
2014-07-08 10:12:27,188 INFO  com.netflix.discovery.DiscoveryClient:992 [main] [makeRemoteCall] Finished a call to service url http://serverIP:8080/eureka/v2/ and url path apps/SAMPLESERVICE/defonds-win7 with status code 200.
2014-07-08 10:12:27,189 INFO  com.netflix.discovery.DiscoveryClient:603 [main] [unregister] DiscoveryClient_SAMPLESERVICE/defonds-win7 - deregister  status: 200
Shutting down server.Demo over.
        麻雀虽小五脏俱全，例子很简单，但却完整地展现了一个 Application Service 客户端的 Eureka 生命周期。
        参考资料

• https://github.com/Netflix/eureka/tree/master/eureka-server/conf
• https://github.com/Netflix/archaius/wiki/Getting-Started