Eureka is part of the Spring Cloud Netflix which is some kind of a service box that can be configured to create a registry of microservice instances. It is shown in this recipe that Eureka provides almost the same configuration procedures in building a server and a client instance. In some scenarios, Eureka can be used to build an application that can be both a server and client for some singleton architectures.
Setting up a service registry is similar to building a large online portal with sub-modules independent from the others, but yet interact with each other and come up with one big infrastructure. Spring Cloud, which is the building block of building this design architecture with Spring Boot 2.0 and microservices, provides many solutions, such as Eureka service, that are easy to configure and use. To build a Eureka server only requires building a Spring Boot application that will wrap Spring Cloud Netflix Eureka services in its pom.xml and enable loading of all the services at bootstrap level using the annotation @EnableEurekaServer. Likewise, the same starter POM dependencies are needed to build Eureka clients which are basically the microservices per se. Each microservice just needs to apply the @EnableDiscoveryClient annotation in its bootstrap to load all the necessary services needed to automatically register each instance to the Eureka server.
Proper Eureka server and client configurations also depend on the configuration details reflected from their application.properties file. As shown by the recipe above, there are Eureka server properties such as eureka.client.register-with-eureka and eureka.client.fetch-registry that must not be present in any Eureka client configurations. On the other hand, clients must declare some additional necessary settings for the Eureka server to know the exact details of its instances. Just in case, when a client fails to register during its first heartbeat, the server will give a chance to the instance and waits for 30 seconds (eureka.instance.leaseRenewalIntervalInSeconds ) to explicitly register itself. This property can also be overridden to tell the server to decrease or increase the server waiting time. Likewise, the client needs to override the default property eureka.instance.leaseRenewalIntervalInSeconds to quickly declare an instance at dead state. The Eureka server can also add some property, such as disabling eureka.instance.enableSelfPreservation, which is not recommended for complex architectures.
To resolve some compatibility issues, the only Spring Cloud release that is built using Spring Boot 2.0 is the SpringBootFinchley version.