Meetup Micro-services

The project explores micro-service oriented application design with use of CQRS principle:

It consists of two services:

• users-api - provides REST API to clients and implements the Query part of CQRS. It uses Elasticsearch as projection repository updated by events generated by users-handler.
• users-handler - implements the Command part of CQRS and uses h2 database for persistence.

The services communicate via JMS bus provided by Apache ActiveMQ.

More detailed design documentation is available here.

Prerequisities

Install Docker Machine and Compose: http://docs.docker.com/machine/install-machine/

Build and Run

git clone https://github.com/benzohub/meetup.git

cd meetup

./gradlew buildDocker

./runall

If everything went well, you should see a lot of log messages in the console without errors among them ;)

Visit the following urls:

http://192.168.99.100:8080/users - list of registered users

http://192.168.99.100:8161/admin/queues.jsp - ActiveMQ Admin page listing queues

192.168.99.100 is the default IP of the docker VM. It can be retrieved by calling:

docker-machine ip default

Create new user

curl -XPOST 'http://192.168.99.100:8080/users' -H 'Content-Type: application/json' -d '{ "userName" : "eupestov", "userFullName" : "Eugene Pestov" } '

curl -XPOST 'http://192.168.99.100:8080/users' -H 'Content-Type: application/json' -d '{ "userName" : "bonny", "userFullName" : "Bonny Nord" } '

Create new users connection

curl -XPOST 'http://192.168.99.100:8080/users/eupestov/connections' -H 'Content-Type: application/json' -d '{ "userName" : "bonny" } '

The API Specification is available in docs/api in RAML format.

UI

After the services started successfully you can run the simplistic UI as described in ui/README.md

Scalability

In order to make this application truly scalable and resilient it requires an addition of few infrastructure elements e.g.:

• API Gateway to proxy and load-balance instances of api modules. It will also inject security context. (a possible candidate: Netflix Zuul)
• API Registry to provide the API Gateway with information about available services and their location (Netflix Eureka)
• Replace the built-in Elasticsearch instance in the api module with a cluster

Future developments

• At the moment the service implements only sunny day scenarios and have no error handling in place.
• The messaging infrastructure needs to be improved to support guaranteed delivery.
• handler services should probably implement Event Sourcing patters with actual Event Store implementation rather that a RDBMS.

Testing

There is one test example in the api module which demonstrates possibility for contract (RAML-based) and integration testing.

The following parts require better unit test coverage:

• core: ActionDispatcherImpl, ActionJmsListenerEndpoint, SimpleJsonMessageConverter
• handler: command handlers, custom repository methods
• api: controllers, services

The test coverage should be calculated during every CI build and uploaded into Sonar Cube.