Developing mocroservices with SpringBoot

There is a trend towards microservices from monolith applications running on a a single application server. The application now becomes a set of loosely coupled modules which communicate with each other through APIs. The benefits are:

• Modularity
• Scalability by functional decomposition
• Fault isolation - failure in one service doesn't bring down the entire application
• No long term commitment to a single technology stack
• Developer productivity - each service can be developed and deployed independently
• Easier to understand - a service does just one task

The challenges:

SpringCloud provides abstractions and utility services for developing and running microservices. This is a small project to get my hands dirty and understand different tools and services offered by SpringCloud to develop SpringBoot microservices. The project is based on presentation by Josh Long for Cloud Native Java in SpringOne (insert YouTube link here)

Application

The application is just two services - user service to manage users and activity service to manage activities for the users.

Running MongoDB in Docker

We are going to use MongoDB for persistence. Although we could just install and run a mongodb instance on a server, the idea is to be able to automate installing and running a Mongo instance. We will dockerize SpringBoot services as well and have all of our services running on Docker.

$ docker run -P -d --name mongo mongo

See Docker for instructions on how to install Docker on Mac or Windows.

Configuration management with Spring Cloud Config Server

Spring Cloud Config provides externalised configuration management for distributed applications. The properties that are contained in application.proerties are now served by config server. The config server uses a git repository to manage property files for the different applications that depend on it for their properties.

Generate a config server template project by using http://start.spring.io and selecting the config-server from Cloud Configuration options.

config-server folder in this repo contains our config server. Key point to note, the application.properties contains the following entries:

spring.cloud.config.server.git.uri=${HOME}/Desktop/config management.security.enabled=false server.port=8888

The property spring.cloud.config.server.git.uri specifies the location of the git repository containing application properties.

Eureka Service Discovery

Microservices

The actual services that we set out to write.

User service

User service provides API end points for adding and updating users. This is also generated as as SpringBoot application using http://start.spring.io and selecting the options

• Web - For REST endpoints
• MongoDB - SpringData for MongoDB
• Config Client - User externalised configuration from config server
• Eureka Discovery - Service registration and discovery using Eureka
• Actuator - Out of box OPs console for SpringBoot app

The application contains bootstrap.properties to specify config server details and the applicaton name:

spring.application.name=user-service spring.cloud.config.uri=http://localhost:8888

The folder user-service in this repository contains code base for user-service, to run simply gradle bootRun.

Activity service

Edge Server (Client proxy)

Circuit breaker with Hystrix

Loadbalancing

CQRS with messaging