Skiza Postback Server

A blog post is available here

Motivation

• A number of scenarios with third party integrations require the need for a web hook to receive the response.
• Case where a certain action is not completed immediately or is asynchronous, some partners opt to send a final response to a web hook.
• For example, Safaricom Daraja sends the final transaction status and info as a postback/callback to a designated http endpoint;
• Therefore, in development scenarios debugging can be hard as you need to create an internet-reachable http endpoint where you'll receive your postbacks.
• This tool helps you t-shoot this scenario by providing a convenient way for you to quickly receive these postbacks.
• Have your third party send the postbacks to this app via the endpoint /api/postbacks and they are streamed real-time to a friendly web UI or Postman Stream where you can inspect and t-shoot.

Running and Developing locally

# Terminal 1
cd frontend
npm i
# npm run dev # run the dev server * DONT Use this option
npm run build
npm run preview # test SSE

# Terminal 2
cd backend
mvn spring-boot:run # resolve dependencies and start the spring-boot server

Testing

Access Browser Vite Preview Build at http://localhost:4173/

Postman/Curl - curl --location 'localhost:8080/api/postbacks/stream'

Send a sample postback to test

curl --location 'localhost:8080/api/postbacks' \
--header 'Content-Type: application/json' \
--data '{
    "name": "Hello SSE"
}'

Design

Backend

• Spring Webflux
• Two API endpoints POST /api/postbacks to receive postback and GET /api/postbacks/stream to stream postbacks.
• See PostbackController.java for Implementation.

Frontend

• Daisy UI
• Vite + React TS
• Browser Support for EventSource
• See Table.tsx for Implementation Logic.

Gotcha's

You should not perform the browser test using vite dev server http://localhost:5173/ because of how React StrictMode behaves in development. Strict Mode will mount, unmount and mount again the Table Component, and therefore connection to SSE will be broken.

Expose to the Internet Via ngrok

To receive postbacks on your local setup, you can expose the postback endpoint via ngrok

1. Create an account at ngrok

2. On the backend directory shell cd backend use your favorite 21 JDK sdk use java 21-librca

3. Ensure docker is running and build a docker image using spring boot cloud native build pack ./mvnw spring-boot:build-image

4. Create an .env file at project root cp .env.example .env

   • Confirm you are on project root/directory you cloned into

   ls
   # README.md       backend         compose.yml     demo            frontend

   • Create an .env file

      cp .env.example .env

5. Get your NGROK AUTH TOKEN from ngrok Dashboard

   
   

6. Add it to .env file NGROK_AUTH_TOKEN='YOUR_NGROK_AUTH_TOKEN'

7. Run Docker Compose docker compose up

8. Your ngrok endpoint can be seen at the dashboard

   
   

9. Back to your postman or Table.tsx replace localhost:8080 with the ngrok endpoint, you can even use it on partner sandbox as its accesible on the internet.