Notification

• Notification
  • Application Overview
    • Rate Limiting mechanism
    • Idempotency
  • Development
    • Prerequisites
    • Getting Started
    • Helper Scripts
    • OpenAPI Documentation
    • Testing

Application Overview

This is a Notification system that supports notifications through email.

Rate Limiting mechanism

There's a rate-limiting mechanism in place based on a Leaky Bucket algorithm, where some rules are enforced based on the notification type.

Notification type	Max count	Expiration
Status	2	1 minute
News	1	24 hours
Marketing	3	1 hour

Idempotency

This system ensures idempotency of notification message processing, meaning that no duplicates are processed in case of accidental message sending caused by system failure, malfunctioning of upstream sender services, or even, race conditions in a multiple replica environment of this application itself.

The idempotency violation is based on the correlationId identifier that must come as part of the JSON request body when sending notifications through this application.

Important

As of now, duplicates are detected in a time span of 24 hours, which should be enough to prevent most issues, meaning that, if for some reason, the same correlation ID is sent after 24 hours, it will be considered a whole new notification.

Development

Prerequisites

• Go v1.23+
• Make: required by the helper scripts
• Docker
• Mockery: to generate and update mocks
• Swag CLI v1.8.4: to generate and update OpenAPI specs*

Warning

Swag must be installed in a specific version of v1.8.4 because of some issues recognizing annotations in dependency files.

Getting Started

The easiest way to get started is by running the Docker stack defined in this project, so that all settings and dependency services are set up altogether without any overhead.

Running the application directly

First, refer to template.env to export the necessary environmental variables to configure the application.

Will spin up the application from your terminal

make run

The application will be running at localhost:8080

Replace 8080 with the port you defined if you chose a different one.

curl http://localhost:8080/healthz -v

Running the application from a Docker container

Will spin up the application container

make docker-up

The application will be running at localhost:8080

curl http://localhost:8080/healthz -v

Update the docker container with your recent changes

make docker-update

Test the API

Send a notification through the API:

curl -X 'POST' \
  'http://localhost:8080/send' \
  -H 'Content-Type: application/json' \
  -d '{
  "correlationId": "0990cc56-f1b7-4f69-bc60-08fac22d41bj",
  "message": "Hey there!",
  "type": "status",
  "userId": "123-abc"
}'

The correlation ID must be different for every different request.

Check the email inbox

Go to MailHog's UI to check if the message has arrived to the inbox. You should be able to see the notification message you just sent with the subject "Status: there's a new status update".

Helper Scripts

For commonly used tasks and commands, there are quite a few helper commands added to the Makefile of this project available for the make command, so make sure to check the file out to get to know the full list.

OpenAPI Documentation

Once the application is up and running, you should be able to access the Swagger endpoint, where the OpenAPI specifications for the routes implemented are parsed: http://localhost:8080/swagger/index.html

Testing

Run the unit tests suite

make test

Run the unit tests suite while generating a coverage report

make test-cov

Render the test coverage report as HTML

make show-cov

Back to top