Description

This is a very barebones minimal example of setting up two separate nest APIS which run independently but are connected through a microservice. For the sake of simplicity both apps have been committed to the same repo, but these could live each in their own repository. They each have a different url, different database, and their own endpoints, and connect through a nestjs microservice.

I am using TCP but Redis and RabbitMQ can be easily swapped in with minimal changes

The "Subscriber + MicroService"

• runs on port 8000 in local (would be deployed independently and have it's own baseURL)
  • This is only if you want to expose this API... it is not necessary if you only want to run the microservice from this app. Running both allows you to have a microservice within an existing application which communicates with the provider, while also having exposed endpoints for other bussiness
• calls two instances of "app.listen":
  • main.ts: NestFactory.create(), exposes the endpoints and CRUD operations of the application.
  • listen.ts: NestFactory.createMicroservice(), which listens to messages and events sent or emitted from the client in the Provider Application using the @EventPattern and @MessagePattern
• has two root configs: nest-cli.json and listen.json

The "Provider"

• runs on port 8001 in local (would be deployed independently and have it's own baseURL)
• main.ts: Calls NestFactory.create() -> app.listen()
• has an instance of CreateClientProxy from nestjs microservices within the Provider Module.
  • this client proxy is injected into the Provider controller, and whenever we hit these endpoints, the client proxy will send or emit data and commans to the listener in the Subscriber app, which retrieves the data from within the subscription database and sends it back to the clientProxy in the Provider

Testing out the Microservice

Currently there is only one function passing hardcoded data. WIP.

If you hit the /api/provider endpoint with a GET request you will see the data logged in the terminal where you have ran app.listen()

Dependencies

• Node
• npm or yarn pkg manager
• nest cli
  • nestjs/micrservices
  • nestjs/common
  • nestjs/config
  • typeorm
  • nestjs/typeorm
  • pg
  • hapi/joi
  • class transformer

Installation - Subscriber

$ npm install

Running the Subscriber/Microservice Listener

**Open a new terminal**
# watch mode
$ npm run listen

Running the Subscriber API

**Open a new terminal**
# watch mode
$ npm run start:dev

Installation - Provider

$ npm install

Running the Provider API

**Open a new terminal**
# watch mode
$ npm run start:dev

Links To Sources

Antonio Papa - Scalable Scripts

• Youtube video
• This guy is my favourite.
• Easy to follow youtube video. Prior nestjs experience would be helpful for this tutorial.
• About half way through he starts on the microservices stuff, the first half is just nestjs and typeorm set up for two apps.
• He explains how to set up two listeners from the same app.

Brian Johnson

• Another youtube video. 4 part series, focuses just on the microservice stuff.
• I found this one to be missing some steps and also had to troubleshoot a few errors that weren't covered in the tutorials (very likely this was my bad).
• He does a good job explaining some of the concepts and setting up gRPC ( grpc is last video in the series )

Official Nestjs docs

License

MIT licensed.