Scaling Spring Boot Microservices

It is an example how to scale Spring Boot microservices based on a chat application.

How to build frontend

1. Move to frontend/chatapp dir
2. Run npm install
3. Run npm run build

After that Spring will use build dir as a source for static files.

How to run backend

1. Build frontend
2. docker/docker-compose.yml contains all necessary datasources (PostgreSQL, RabbitMQ, Redis). Run it with docker-compose up -d command.
3. Run backend with a command ./mvnw spring-boot:run -Dspring-boot.run.arguments=--server.port=8080. Use different ports if you want to run multiple instances simultaneously.
4. Go to http://localhost:8080. Migrations will create 6 users: Neo, Boris Britva, Gendalf, Thor, Forrest Gump and Tyler Durden with 123 passwords.

Branches

1. master branch contains initial state of the application that is not scalable.
2. scalable branch contains fully-scalable application, using RabbitMQ as an external message broker, Redis for cache, and PostgreSQL for sessions.
3. scalable-crazy branch contains an example of an approach to fix a problem of @SubscribeMapping in a BeanPostProcessor manner. It is fully-scalable, but has a huge disadvantage - every subscribed user gets an initial response.
4. scalable-manual-shedlock branch shows how to use ShedLock manually without annotations.