PowerSync Node.js + Firebase Backend: Demo

Overview

This repo contains a demo Node.js server application which has HTTP endpoints to authorize a PowerSync enabled application to sync data between a client device and a PostgresSQL database. In addition, it has endpoints that allow a PowerSync client to authenticate.

The endpoints are as follows:

1. GET /api/auth/token

   • PowerSync uses this endpoint to retrieve a JWT access token which is used for authentication.

2. GET /api/auth/keys

   • PowerSync uses this endpoint to validate the JWT returned from the endpoint above.

3. PUT /api/data

   • PowerSync uses this endpoint to sync upsert events that occurred on the client application.

4. PATCH /api/data

   • PowerSync uses this endpoint to sync update events that occurred on the client application.

5. DELETE /api/data

   • PowerSync uses this endpoint to sync delete events that occurred on the client application.

The repo also has an integration with Firebase to validate a token provided in the header of the /api/auth/token endpoint.

Packages

• node-postgres is used to interact with the Postgres database when a PowerSync enabled client performs requests to the /api/data endpoint.
• jose is used to sign the JWT which PowerSync uses for authorization.
• firebase-admin is used to connect to Firebase and the verifyIdToken function is used to validate the client application request before the app generates a JWT used by PowerSync to sync data.

Requirements

This app needs a PostgresSQL instance that's hosted. For a free version for testing/demo purposes, visit Supabase.

Running the app

1. Clone the repository

2. Follow the steps outlined in PowerSync Custom Authentication Example → Generate a key-pair to get the key pair you need for this app. This is an easy way to get started with this demo app. You can use your own public/private keys as well.

3. Create a new .env file in the root project directory and add the variables as defined in the .env file:

cp .env.template .env

4. Make sure to place a copy of your Firebase Admin SDK serviceAccountKey.json in the root of the project.

   4.1. You can get this file from the firebase console by heading over to your project settings > Service accounts > Firebase Admin SDK > Generate new private key

   4.2. Download the json file and save it in the project root as serviceAccountKey.json.

   4.3. Set the GOOGLE_APPLICATION_CREDENTIALS to point to the file on your machine e.g

   GOOGLE_APPLICATION_CREDENTIALS= /path/to/powersync-nodejs-firebase-backend-todolist-demo/serviceAccountKey.json
   

5. Install dependencies:

This demo requires node to be installed on your system. Alternatively you can install it using nvm.

yarn
or
npm install

Start App

1. Run the following to start the application

npm run start
or
yarn start

This will start the app on http://127.0.0.1:PORT, where PORT is what you specify in your .env file.

2. Test if the app is working by opening http://127.0.0.1:PORT in the browser

3. You should get a JSON object that looks like this as the response

{ "message": "powersync-nodejs-backend-todolist-demo" }

Testing the app with PowerSync

This process is only designed for demo/testing purposes, and is not intended for production use. You won't be using ngrok to host your application and database.

1. Download and install ngrok

2. Run the ngrok command to create a HTTPS tunnel to your local application

ngrok http <YOUR PORT>

This should create the tunnel and a new HTTPS URL should be available e.g.

ngrok by @inconshreveable                                                                                                                  (Ctrl+C to quit)

Session Status                online
Account                       Michael Barnes (Plan: Free)
Update                        update available (version 2.3.41, Ctrl-U to update)
Version                       2.3.40
Region                        United States (us)
Web Interface                 http://127.0.0.1:4040
Forwarding                    http://your_id.ngrok-free.app -> http://localhost:8000
Forwarding                    https://your_id.ngrok-free.app -> http://localhost:8000

Connections                   ttl     opn     rt1     rt5     p50     p90
                              1957    0       0.04    0.03    0.01    89.93

3. Open the PowerSync Dashboard and paste the Forwarding URL starting with HTTPS into the Client Auth tab of your PowerSync instance e.g.

JWKS URI
https://your_id.ngrok-free.app/api/auth/keys/

Pay special attention to the URL, it should include the /api/auth/keys/ path as this is used by the PowerSync server to validate tokens.