Declare separate Firebase Cloud Functions and still use Express.js

Question

There are many examples of using Express for Firebase Cloud Functions.

In every example of I have found the code exposes the Express app as a single Cloud Function:<

Answer 1

Thanks to Doug Stevenson for his answer and help. I wanted to provide my own answer though.

So the answer to my question is, generally speaking: no you can't.

As Doug was pointing out, this is not a problem for many people's scaling needs. Firebase will create up to 1,000 instances of your function to scale.

I wanted to provide a slightly different answer then Doug's to how I would write an Express app and have different Firebase Cloud Functions for a project:

const payment = express()
const order = express()
payment.get('/route', ...)
order.get('/route', ...)
export const payment = functions.https.onRequest(payment)
export const order = functions.https.onRequest(order)

The advantage here is that I can start to express REST or RPC routes like:

• /payment/someaction (RPC)
• /order (get,put,post, etc.)

Another benefit is that I can provide a "test" API and a "live" API for things like credit card payments/processing:

// [START Express LIVE App]


// [START get user]
app.get('/user', async (req, res) => {
  await handleGetUser(req, res, paymentServiceLive);
});
// [END get user]

// [START claim]
app.post('/claim', async (req, res) => {
  await handleClaim(req, res, claimEmailTo);
});
// [END claim]

// [START user]
app.post('/user', async (req, res) => {
  await handleUserPost(req, res, paymentServiceLive);
});
// [END user]

// [START ephemeralKey]
app.post('/ephemeralKey', async (req, res) => {
  await handleEphemeralKey(req, res, paymentServiceLive);
});
// [END ephemeralKey]


// [START charge]
app.post('/charge', async (req, res) => {
  await handleCharge(req, res, paymentServiceLive);
});
// [END charge]

// [START purchase]
app.post('/purchase', async (req, res) => {
  await handlePurchase(req, res, paymentServiceLive);
});
// [END purchase]

//Expose Express API as a single Cloud Function:
exports.app = functions.https.onRequest(app);

// [END Express LIVE App]



// [START Express TEST App]

// [START get user]
appTest.get('/user', async (req, res) => {
  console.log('appTest /user get', req);
  await handleGetUser(req, res, paymentServiceTest);
});
// [END get user]

// [START claim]
appTest.post('/claim', async (req, res) => {
  await handleClaim(req, res, claimEmailToTest, true);
});
// [END claim]


// [START user]
appTest.post('/user', async (req, res) => {
  console.log('appTest /user post', req);
  await handleUserPost(req, res, paymentServiceTest);
});
// [END user]

// [START ephemeralKey]
appTest.post('/ephemeralKey', async (req, res) => {
  await handleEphemeralKey(req, res, paymentServiceTest)
});
// [END ephemeralKey]


// [START charge]
appTest.post('/charge', async (req, res) => {
  await handleCharge(req, res, stripeTest);
});
// [END charge]

// [START purchase]
appTest.post('/purchase', async (req, res) => {
  await handlePurchase(req, res, paymentServiceTest);
});
// [END purchase]

//Expose Express API as a single Cloud Function:np
exports.apptest = functions.https.onRequest(appTest);

// [END Express TEST App]

This allows me to have a development environment and a live environment. in my app config files I just have a different API url:

/us-central1/apptest

or

/us-central1/app