Simple Microservice Example

A very simple microservice example with NodeJS, Python, Redis, and Mongo

Dependencies

API Gateway/FrontendApplication

• Node

Data Backends

• MongoDB
• Redis

QuoteService

• python3
• pip3
• flask
• pymongo
• redis

Hosting

• NGINX

Runtime configuration

The services are configured with environment variables so the same code can run under systemd, Docker Compose, Kubernetes, and CI/CD.

API Gateway

• QUOTES_API - required. Base URL for the QuoteService, for example http://localhost:5000.
• PORT - optional, defaults to 3000.
• APP_ENV, APP_VERSION, BUILD_SHA, BUILD_TIME - optional metadata returned by /api/version.

QuoteService

• MONGO_HOST - required.
• MONGO_USER - required.
• MONGO_PASSWORD - required.
• REDIS_HOST - required.
• MONGO_PORT, MONGO_AUTH_SOURCE, MONGO_DB, MONGO_COLLECTION, REDIS_PORT, REDIS_PASSWORD, PORT - optional.
• APP_ENV, APP_VERSION, BUILD_SHA, BUILD_TIME - optional metadata returned by /version.

See .env.example for a local development example.

Contract tests

The repository includes a small end-to-end contract test suite. Once the whole application is reachable from a single base URL, run:

make test-e2e BASE_URL=http://localhost:8080

The tests verify the frontend, gateway status, health/readiness, version metadata, seeded Mongo data, Redis-backed quote counts, request IDs, and the quote create/read path.

Build the frontend

The application uses a frontend written with plain html with jQuery and to style with Bulma.

This is built with webpack. By default the frontend calls same-origin /api routes, which works well when NGINX proxies /api/ to the API Gateway.

To build this to fit your own IP Address please follow the steps before running the whole microservice.

• Install NodeJs on your system

• Go to FrontendApplication directory

• Run npm install or if you have yarn yarn to install packages

• Now you need to set the API Gateway for this frontend application. It can be any host you have.

  • Let's say you are hosting this application on http://example.com then your API_GATEWAY would be this one.
  • If you are hosting in some machine with IP 123.324.345.1 then your API_GATEWAY would be your IP.
  • If the frontend and API are served from the same base URL, leave API_GATEWAY unset.

• To pass this setting to webpack build you need to set an Environment Variable

  • Windows : set API_GATEWAY=http://YOUR_HOST
  • Linux/Max : export API_GATEWAY=http://YOUR_HOST
  • Remember no / at the end of the URL to get your web app work
  • You will need to add a port if not using standard ports

• Now you can do npm run build or yarn build

• Check dist/ folder for newly created index.html and the main.js

• Copy dist/ folder contents to /var/www/html to overwrite the default nginx files.

Initialize MongoDB

Follow the instructions from Mongo to install MongoDB on Ubuntu.

Make sure to run the systemd(systemctl) instructions at the end to enable and start MongoDB running as a background service.

Finally make sure you initialize the database admin user and database with starter data.

mongosh < MongoDB/admin-init.js
mongosh < MongoDB/init-db.js

Run MongoDB/init-db.js against the quote_db database to seed the quote collection. The script is idempotent and can be run more than once without duplicating seed records.

Initialize Redis

Follow the instructions from Redis to install Redis on Ubuntu.

Then enable/start redis running as a daemon service.

sudo systemctl enable redis-server
sudo systemctl start redis
sudo systemctl status redis

QuoteService Service

Create a python virtual environment and install the dependencies

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Set the required MongoDB and Redis environment variables in your shell, systemd service, Docker Compose file, or Kubernetes manifests. Then update the quote.service file to match your local paths to python and your code. Copy the quote.service file to /etc/systemd/system/quote.service and then enable the QuoteService daemon service.

sudo systemctl daemon-reload
sudo systemctl enable quote.service
sudo systemctl start quote

API Gateway

• Go to ApiGateway directory

• Run npm install

• Update the environment in the apigateway.service file to point at QuoteService.

  • Environment="QUOTES_API=http://localhost:5000"
  • Use the QuoteService container or Kubernetes service name when deploying in those environments.

Now can deploy API Gateway service. Copy the apigateway.service file to /etc/systemd/system/apigateway.service and then enable the ApiGateway daemon service.

sudo systemctl daemon-reload
sudo systemctl enable apigateway.service
sudo systemctl start apigateway

NGINX

Now we need to update/change the configuration for NGINX.

sudo rm /etc/nginx/sites-enabled/default
sudo cp FrontendApplication/vhost.conf /etc/nginx/sites-available/
sudo ln -s /etc/nginx/sites-available/vhost.conf /etc/nginx/sites-enabled/default
sudo systemctl restart nginx

Final Result

• check http://YOUR_HOST:80 to see web app
• run make test-e2e BASE_URL=http://YOUR_HOST to verify the deployment