SumMetricSystem

A metric logging and reporting service that sums metrics by time window for the most recent hour.

Specification

This service has two endpoints:

• An endpoint to add metric values:

Request:
POST /metric/{key}
{
"value": 30
}

Response: (200)
{}

• Another one to sum the metric values in the last 60 minutes:

Request:
GET /metric/{key}/sum

Response:
{
  "value": 400
}

Some important things:

• Every value added must to be deleted after 60 minutes.
• Every value added must to be rounded to the nearest integer.
• No database/store system is needed, a basic datastructure or file is enough.

Development

This service was developed using node 12.16.x. You need node and npm to make it work.

It was coded using Babel, to support modules and some features of ES6/7 at development time. It has a pretty basic configuration, though. The code can be found at ./src directory.

Note: As AWS Elastic BeanStack is the target to deploy, all scripts in ./package.json were written to work in a *NIX system. So, if you are using Windows 10, you may want to install a Windows Subsystem for Linux (Ubuntu is the most popular).

Also, to make easier the configuration of some variables, the service depends on dotEnv. To tweak the configuration you may edit ./env.dev for development use, or ./env.prod for production.

Start the service

To start the service in order to test it functionally, you just need to run the command: npm run start:dev; and that's it, this command will run the linter, transpile the code, and configure the environment as is needed for development. This start:dev script works on top of nodemon, so every change in the ./src directory will be reloaded automatically.

Once the server is ready to listen, you can use your favorite REST client to hit the URLs:

# To add a metric value
curl \
  -H 'Authorization: Bearer ishallpass' \
  -d '{"value": 123}' \
  -v \
  'http://localhost:3000/metric/visitors'

# To check the sum of values of a specific metric
curl \
  -H 'Authorization: Bearer ishallpass' \
  -v \
  'http://localhost:3000/metric/visitors/sum'

Note: -v is a completely optional flag, but sometimes it helps a lot.

Service structure

The service has a pretty simple structure:

• ./src/.eslintrc.json: Some basic configurations to have some codestyling.
• ./src/auth.js: A simple authorization-simulator middleware.
• ./src/babel.config.json: The babel configuration.
• ./src/index.js: Is the controller file, this handle the http requests.
• ./src/index.test.js: This is the test file for the ./src/index.js
• ./src/model.js: It's a representation of a "data store", and the entity that is "persisted" (A.K.A. the metric).
• ./src/service.js: Here you can find the business logic.
• ./src/service.test.js: This is the test file for the ./src/service.js

Test

You simply need to run the command npm run test, and that will run jest for you.