我是微服务（使用 Spring Boot）的新手。复制生产代码并尝试在我的本地运行。为了成功运行代码我应该做什么？有config服务器、eureka服务器、tomcat服务器、zuul路由工具、ribbon负载均衡器、feign客户端等等。运行应用程序需要哪些必要步骤？配置服务器运行正常，但尤里卡服务器显示问题：
2017-05-02 16:30:01.193 WARN 4860 --- [freshExecutor-0] c.n.d.s.t.d.RetryableEurekaHttpClient : Request execution failure
2017-05-02 16:30:01.195 ERROR 4860 --- [freshExecutor-0] com.netflix.discovery.DiscoveryClient : DiscoveryClient_EUREKA-SERVER/LT-BSSYFY1.XXXXXXX.in:eureka-server:8002 - was unable to refresh its cache! status = Cannot execute request on any known server
com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:111) ~[eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) ~[eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137) ~[eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) ~[eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.DiscoveryClient.getAndStoreFullRegistry(DiscoveryClient.java:1013) [eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.DiscoveryClient.fetchRegistry(DiscoveryClient.java:927) [eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.DiscoveryClient.refreshRegistry(DiscoveryClient.java:1451) [eureka-client-1.4.4.jar:1.4.4]
at com.netflix.discovery.DiscoveryClient$CacheRefreshThread.run(DiscoveryClient.java:1418) [eureka-client-1.4.4.jar:1.4.4]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_121]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_121] …有些地方提到Kafka是发布订阅消息传递。其他消息来源提到 Kafka 是消息队列。请问它们之间有什么区别，Kakfa可以用作数据库吗？