Notifier

This is the notifier app for the NGINX Microservices March demo architecture.

Responsibility

This service listens for notifications of events in the system that might need a notification sent to a user. It then dispatches notifications based on the user's notification preferences.

Requirements

This project requires either NodeJS or Docker to run. Using NodeJS will recreate a local development environment. Using Docker will let you recreate a pseudo production environment.

NodeJS

This project uses NodeJS. The current version is specified in .tool-versions. NodeJS is a rapidly evolving language which makes it critical to explicitly define which version is being used to avoid any potential errors due to mismatched versions.

We recommended that you use asdf to manage your local NodeJS installation. Once you have asdf installed, you can run asdf install to automatically install the version of NodeJS specified in .tool-versions.

Why asdf?

In a microservices environment, you may have to work on projects that use different versions of a runtime like `NodeJS`, or use a different language altogether!

asdf is a single tool that lets you manage multiple versions of different languages in isolation and will automatically install and/or switch to the required runtime/version in any directory that has a .tool-versions file.

This is helpful in getting closer to dev/prod parity in a microservices environment. As you can see in this project, the GitHub action workflow uses the same version called out in .tool-versions to test the codebase and build a Docker image.

This way, if we use asdf we're guaranteed to be developing, testing, and releasing to a consistent version of NodeJS.

You can also install NodeJS by other means - just reference the version number in the .tool-versions file.

Docker

You can run this project on a container using Docker together with Docker Compose. This will let you build a simple reproducible image and forget about setting up your local environment. Instructions on how to install Docker can be found in the Docker website. (Docker Compose is included as part of the recommended Docker installation instructions.)

Setup

Note: Instructions marked as (NodeJS - Dev) are only necessary if you want to recreate a local development environment. Instructions marked as (Docker - Prod) are only necessary if you want to recreate a pseudo production environment (careful, it's not actually production ready!).

1. Clone this repo:

   git clone https://github.com/microservices-march/notifier

2. Start the notifier service PostgreSQL database:

   docker-compose up -d

3. (Docker - Prod) From the root directory of this repository, build the notifier Docker image:

   # in ./app
   docker build -t notifier .

4. (Docker - Prod) Start the notifier service in a container:

   docker run -d -p 5000:5000 --name notifier -e PGPASSWORD=postgres -e CREATE_DB_NAME=notifier -e PGHOST=notifier-db -e AMQPHOST=rabbitmq -e AMQPPORT=5672 -e PORT=5000 -e PGPORT=5433 --network mm_2023 notifier
   

5. (Docker - Prod) SSH into the container to set up the PostgreSQL DB:

   docker exec -it messenger /bin/bash

6. (NodeJS - Dev) Install NodeJS modules:

   # in ./app
   npm install

7. Create the PostgreSQL DB:

   # in ./app
   PGDATABASE=postgres node scripts/create-db.mjs

8. Create the PostgreSQL DB tables:

   # in ./app
   node scripts/create-schema.mjs

9. Create some PostgreSQL DB seed data:

   # in ./app
   node scripts/create-seed-data.mjs

10. (NodeJS - Dev) Start the service:

    # in ./app
    node index.mjs

Using the Service

There is no configuration needed to run this service. When properly configured together with the messenger service, if a new message is sent via that service, you should see log entries in this service detailing any messages that have been sent.

Application Notes

The configuration data for this application can be seen in the configuration schema.

This application serves as a simple example of a service handling events from a message queue and having its own database. However, it intentionally does not do a few things for the sake of simplicity:

• Notifications are not actually sent
• A log of sent notifications is not kept in a queryable way - however it is possible to reference the logs to see dispatch

A Note on Code and Style

The code for this example is written in a style that not in line with application development best practices.

Instead, it is optimized to be quickly understood by those seeking to understand the Microservices March Demo Architecture without assuming special familiarity with:

• Javascript
• NodeJS
• Express

Therefore, we've opted to:

• Avoid frameworks that have domain specific languages (ie, database libraries)
• Avoid splitting up code into many different files

Cleanup

If you want to cleanup any artifacts resulting from running this project, run:

• If you used NodeJS to run the project:

  rm -rf node_modules

• If you used Docker to run the project:

  docker rmi notifier

Development

Read the CONTRIBUTING.md file for instructions on how to best contribute to this repository.

License

Apache License, Version 2.0

© F5 Networks, Inc. 2023