Firebase Cloud Functions: Difference between onRequest and onCall

Question

Going through the docs, I encountered:

...you can call functions directly with an HTTP request or a call from the client .

~ source

there (link in the quote) is a mention about functions.https.onCall .

But in the tutorial here , another function functions.https.onRequest is used, so which one should I use and why? What is the difference/similarity between them?

Documentation for functions.https is here .

Answer 1

The official documentation for those is really helpful, but from the view of an amateur, the described differences were confusing at first.

• Both types , when deployed, are assigned with a unique HTTPS endpoint URL and can be accessed directly.

onCall

• Can be invoked (and this is also the main purpose) directly from the client app.

   functions.httpsCallable('getUser')({uid}) .then(r => console.log(r.data.email))

• It is implemented with user-provided data and automagic context .

   export const getUser = functions.https.onCall((data, context) => { if (!context.auth) return {status: 'error', code: 401, message: 'Not signed in'} return new Promise((resolve, reject) => { // find a user by data.uid and return the result resolve(user) }) })

• The context automagically contains metadata about the request such as uid and token .
• Input data and response objects are automatically (de)serialized.

onRequest

• Firebase onRequest Docs
• Serves mostly as an Express API endpoint.

• It is implemented with express Request and Response objects.

   export const getUser = functions.https.onRequest((req, res) => { // verify user from req.headers.authorization etc. res.status(401).send('Authentication required.') // if authorized res.setHeader('Content-Type', 'application/json') res.send(JSON.stringify(user)) })

• Depends on user-provided authorization headers.
• You are responsible for input and response data.

Read more here Is the new Firebase Cloud Functions https.onCall trigger better?

Answer 2

The main difference between onCall and onRequest for the client is the they way they are invoked. when you define a function using onCall eg

exports.addMessage = functions.https.onCall((data, context) => {
  // ...
});

you invoke on it the client side using firebase function client SDK eg

// on the client side, you need to import functions client lib
// then you invoke it like this:
const addMessage = firebase.functions().httpsCallable('addMessage');
addMessage({ text: messageText })
  .then((result) => {
    // Read result of the Cloud Function.        
  });

more info for onCall: https://firebase.google.com/docs/functions/callable

But if you define you function using onRequest eg

exports.addMesssage = functions.https.onRequest((req, res) { ... res.send(...); }

you can call it using normal JS fetch API (no need to import firebase functions client lib on the client side) eg

fetch('<your cloud function endpoint>/addMessage').then(...)

this is the big difference that you need to consider when deciding on how to define your functions on the server.

more info for onRequest: https://firebase.google.com/docs/functions/http-events