This project provides a template for the basics of Spring-Cloud, a wrapper around Netflix OSS for distributed, cloud-native systems. Like with all Spring-Boot projects any properties can be overriden with JVM parameters.
Euraka is Netflix's service discovery tool. It can be started like so:
cd *eureka
mvn spring-boot:runThe Eureka dashboard can be viewed at http://localhost:8761
Eureka is also Amazon aware. However that is not covered in this demo.
The Config server allows for a centralized place for application configuration. The config server can store configuration via a git cloneable repository, svn, or natively on the fliesystem(using the "native" Spring profile). The config server can be started like so:
cd *config
mvn spring-boot:runApplications using the config server client can refresh their configuration with a POST to http://localhost:PORT/refresh
Note: Configuration injected into code on application start via @Value and @Bean as opposed
to Spring-Boot's ConfigurationProperties can only be refreshed if configuration
classes are annotated with @RefreshScope
Zuul is Netflix's API gateway and reverse proxy. It can be use for a number of things including
authentication. This can be shown in the AuthFilter class. Zuul can be started like so:
cd *zuul
mvn spring-boot:runPlease refer to the Spring-Cloud link in Further Reading to learn about how Netflix uses Zuul.
Hystrix is Netflix's implementation of the Circuit Breaker Pattern. Used properly Hystrix monitors dependent systems and adapts accordingly. In addition, Hystrix provides a monitoring dashboard for consuming Hystrix monitoring streams. The Hystrix dashboard can be started like so:
cd *hystrixThe Hystrix dashboard can be viewed at http://localhost:9000/hystrix
Applications that utilize Hystrix typically host their event streams at http://localhost:PORT/hystrix.stream
Turbine aggregates multiple hystrix streams into a single stream to be viewed on the Hystrix dashboard Turbine can be started like so:
cd *turbine
mvn spring-boot:runThe turbine stream that can be used with the Hystrix dashboard can be found at http://localhost:9001/turbine.stream
Zipkin collects data exposed by Sleuth and provides performance and service depedency visualization. It can be used to diagnose performance bottlenecks and analyze application architecture. Zipkin can be started like so:
cd *zipkin
mvn spring-boot:runThe turbine dashboard can be found at http://localhost:9002
The following are example application that demonstrate how to use different parts of Spring-Cloud
A simple web application that demonstrates a couple ways of consuming a Config Server. In addition, this service demonstrates how to use Sleuth, exporting metrics for use with the Zipkin dashboard. It can be started like so:
cd *crud
mvn spring-boot:runA web application the demonstrates how to use the EurekaClient to resolve application
dependencies for use with the RestTemplate. In addition, this service demonstrates how
to use Hystrix, exposing a Hystrix stream for use with the dashboard and how to use Sleuth,
exporting metrics for use with the Zipkin dashboard. For demonstration purposes it is suggested
that you start two instances of this service so that the following application will take full
use of client-side load-balance via its @LoadBalanced RestTemplate and Ribbon. This service
can be started like so:
cd *service
mvn spring-boot:run -Dserver.port=<port> -Dservice.instance.name=<instance-name>This web appplication demonstrates how to utilized client-side load-balancing via a
@LoadBalanced @RestTemplate. This done by either using Eureka service-discovery,
or by using Standalone Ribbon (Which Netflix OSS uses frequently under the hood).
The Ribbon implementation is current commented out. In addition, this application
utilizes Hystrix and Sleuth like the service above and demonstrates how to hide an
application from service discovery (via register-with-eureka=false). This application
can be started like so:
cd *app
mvn spring-boot:runNote: If hidden from service discovery, the application will not be available from the Zuul API gateway (using the configuration in this template)