Air Quality Service

A RESTful API service responsible for providing air quality information of the nearest city to given GPS coordinates using the IQAir APIs.

Technologies:

• TypeScript.
• NodeJS.
• Express.
• MongoDB.

Components

MongoDB database

The primary database where air quality data is stored in a collection named airqualities. This data mirrors the structure returned by the IQAir API.

Example document:

{
  "latitude": 2.352222,
  "longitude": 2.352222,
  "pollution": {
    "ts": "2024-07-05T13:00:00.000Z",
    "aqius": 56,
    "mainus": "p2",
    "aqicn": 29,
    "maincn": "p1"
  },
  "createdAt": {
    "$date": "2024-07-05T13:56:01.027Z"
  },
  "__v": 0
}

API server

An Express-based API server that provides two main endpoints:

Get pollution data of the nearest city

Endpoint: GET /air_quality/nearest_city?latitude=<latitude>,longitude=<longitude>

Retrieves pollution information for the nearest city to the specified coordinates.

Parameters:

• latitude: Latitude as a numerical value, within the range [-90, 90].
• longitude: Longitude as a numerical value, within the range [-180, 180].

Example response:

{
    "pollution": {
        "ts": "2024-07-06T00:00:00.000Z",
        "aqius": 62,
        "mainus": "p2",
        "aqicn": 21,
        "maincn": "p2"
    }
}

Get the most polluted data for Paris

Endpoint: GET /air_quality/paris_most_polluted_info

Retrieves the pollution data for the time when the Paris area (latitude: 48.856613, longitude: 2.352222) was the most polluted.

Example response:

{
    "pollution": {
        "ts": "2024-07-06T00:00:00.000Z",
        "aqius": 62,
        "mainus": "p2",
        "aqicn": 21,
        "maincn": "p2"
    }
}

CRON job

A cron job runs every minute (configured via the PARIS_TASK_TIME environment variable) to poll pollution data for Paris and save it to the database.

This job operates as a separate workload to allow independent scaling of the cron job and the main API server.

Usage

All services can be run using Docker Compose.

Create a .env.dev file to start the Docker Compose services. You can use the .env.template file as a template.

You need to replace the IQAIR_API_KEY env variable value placeholder with your actual IQAir API key.

To start the Docker Compose services, run:

docker-compose -f docker-compose.yml up

# or
make up

To stop the Docker Compose services, run:

docker-compose -f docker-compose.yml down

# or
make down

To run tests you need to create a .env.test file similiar the .env.template. Then run:

docker-compose -f docker-compose.test.yml up

# or
make test

All Docker volume mounts for services will be located in the docker git-ignored directory.

Docker commands are included in a Makefile. Run make help to see the available rules.