1.Consider the following:
If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).
出现这种原因就是服务提供者比Eureka先启动，或者Eureka服务可能没有启动，等Eureka启动后再启动服务提供者。
2.No instances found of configserver (config-server)
可能是启动类中少了注解@EnableDiscoveryClient
3.Cannot execute request on any known server
这种错误是Eureka启动类中少了注解@EnableEurekaServer
