Spring Cloud Netflix

Spring Cloud Netflix is perhaps the most popular Spring module nowadays. This fantastic project allows us to integrate the Spring ecosystem with the Netflix OSS via Spring Boot AutoConfiguration features. The supported Netflix OSS libraries are Eureka for service discovery, Ribbon to enable client-side load balancing, circuit breaker via Hystrix to protect our application from external outages and make the system resilient, the Zuul component provides an intelligent routing and can act as an edge service. Finally, the Feign component can help developers to create HTTP clients for REST APIs with a couple of annotations.

Let's look at each of these:

• Spring Cloud Netflix Eureka: The focus of this project is to provide service discovery for applications while conforming to Netflix standards. Service discovery is an important feature and enables us to remove hardcoded configurations to supply a hostname and ports; it is more important in cloud environments because the machine is ephemeral, and thus it is hard to maintain names and IPs. The functionality is quite simple, the Eureka server provides a service registry, and Eureka clients will contact its registers themselves.

• Spring Cloud Feign: The Netflix team created the Feign project. It's a great project that makes the configuration of HTTP clients for REST applications significantly easier than before. These implementations are based on annotations. The project supplies a couple of annotations for HTTP paths, HTTP headers, and much more, and of course, Spring Cloud Feign integrates it with the Spring Cloud ecosystem through the annotations and autoconfiguration. Also, Spring Cloud Feign can be combined with the Eureka server.

• Spring Cloud Ribbon: Ribbon is a client-side load balancer. The configuration should mainly provide a list of servers for the specific client. It must be named. In Ribbon terms, it is called the named client. The project also provides a range of load-balancing rules, such as Round Robin and Availability Filtering, among others. Of course, the framework allows developers to create custom rules. Ribbon has an API that works, integrated with the Eureka server, to enable service discovery, which is included in the framework. Also, essential features such as fault tolerance are supported because the API can recognize the running servers at runtime.

• Spring Cloud Hystrix: An acclaimed Netflix project, this project provides a circuit breaker pattern implementation. The concept is similar to an electrical circuit breaker. The framework will watch the method marked with @HystrixCommand and watch for failing calls. If the failed calls number more than a figure permitted in configuration, the circuit breaker will open. While the circuit is open, the fallback method will be called until the circuit is closed and operates normally. It will provide resilience and fault-tolerant characteristics for our systems. The Spring ecosystem is fully integrated with Hystrix, but it works only on the @Component and @Service beans.