NKOSL Counter App

Running

The application uses NodeJS, Redis, and Postgres.

To run the application:

npm ic
npm start

Docker

A dockerfile is provided for the application.

A sample docker-compose.yaml is also provided to start the application.

To run the application with docker-compose:

1. Copy the .env.example file to .env and change the required values.
2. Edit the docker-compose.override.yaml file to expose the ports and change whatever you need to do.
3. Run the following command:

   docker compose up --build

Usage

The application is a simple counter app. You can add counters and increment them.

There are 4 endpoints:

• GET / - Get list of all counters
  • Response:

    {
      "counters": [
        {
          "name": "a-counter",
          "count": 1
        },
        {
          "name": "another-counter",
          "count": 42
        }
      ]
    }

• POST / - Add a new counter
  • Request:
    • Content-Type: application/json
    • Body: json { "name": "a-name-for-the-counter", }
  • Response:

    {
      "name": "a-name-for-the-counter",
      "count": 0
    }

• GET /:name - Get a specific counter by name
  • Response:

    {
      "name": "a-name-for-the-counter",
      "count": 1
    }

• POST /:name - Increment a specific counter by name
  • Request:
    • No body is required
  • Response:

    {
      "name": "a-name-for-the-counter",
      "count": 2
    }

All error responses are of format:

{
  "error": "a-name-for-the-counter already exists"
}

All requests contain special headers:

• X-Request-Count - Total request count for that instance. All requests are counted.
• X-Request-Id - A unique request id for that instance. Will be reflected in the logs.
• X-Instance-Id - A unique instance id generated at boot. Will be reflected in the logs.

Example usage

GET /

curl -sL -v http://$APPLICATION_INSTANCE/

> GET / HTTP/1.1
> Host: $APPLICATION_INSTANCE
> User-Agent: curl/8.7.1
> Accept: */*
>
< HTTP/1.1 200 OK
< X-Powered-By: Express
< X-Request-Count: 1
< X-Request-Id: lupv9zmo-24osryu5k
< X-Instance-Id: lupv2g6p-fcci7o683
< Content-Type: application/json; charset=utf-8
< Content-Length: 43
< ETag: W/"2b-AfxlJ6swYwUAObR/CvN8/kq70bs"
< Date: Sun, 07 Apr 2024 18:38:24 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
<
{
  "counters": [
    {
      "name": "a-counter",
      "count": 3
    }
  ]
}

POST /

curl -sL -v --header 'content-type: application/json' --data '{"name": "another-counter"}' http://$APPLICATION_INSTANCE/

> POST / HTTP/1.1
> Host: $APPLICATION_INSTANCE
> User-Agent: curl/8.7.1
> Accept: */*
> content-type: application/json
> Content-Length: 27
>
< HTTP/1.1 200 OK
< X-Powered-By: Express
< X-Request-Count: 2
< X-Request-Id: lupvdapb-qhgjgf73p
< X-Instance-Id: lupv2g6p-fcci7o683
< Content-Type: application/json; charset=utf-8
< Content-Length: 36
< ETag: W/"24-ndFGb0aJNAQ3gj7T5CFG/kxRKCk"
< Date: Sun, 07 Apr 2024 18:40:58 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
<
{
  "name": "another-counter",
  "count": 0
}

POST /another-counter

curl -sL -v -X POST http://$APPLICATION_INSTANCE/another-counter

> POST /another-counter HTTP/1.1
> Host: $APPLICATION_INSTANCE
> User-Agent: curl/8.7.1
> Accept: */*
>
< HTTP/1.1 200 OK
< X-Powered-By: Express
< X-Request-Count: 3
< X-Request-Id: lupvfm0j-1mqqf5hgs
< X-Instance-Id: lupv2g6p-fcci7o683
< Content-Type: application/json; charset=utf-8
< Content-Length: 36
< ETag: W/"24-9fUk8d/x2CZDUJFRlVCIyQ/T21I"
< Date: Sun, 07 Apr 2024 18:42:46 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
<
{
  "name": "another-counter",
  "count": 1
}

GET /another-counter

curl -sL -v http://$APPLICATION_INSTANCE/another-counter

> GET /another-counter HTTP/1.1
> Host: $APPLICATION_INSTANCE
> User-Agent: curl/8.7.1
> Accept: */*
>
< HTTP/1.1 200 OK
< X-Powered-By: Express
< X-Request-Count: 4
< X-Request-Id: lupvgrz0-k2hg9mov0
< X-Instance-Id: lupv2g6p-fcci7o683
< Content-Type: application/json; charset=utf-8
< Content-Length: 36
< ETag: W/"24-9fUk8d/x2CZDUJFRlVCIyQ/T21I"
< Date: Sun, 07 Apr 2024 18:43:41 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
<
{
  "name": "another-counter",
  "count": 1
}