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 using an https client.

• However, there is one important difference in the way how they are supposed to be called.

  • onCall: from the client's firebase.functions()
  • onRequest: via standard https client (e.g. fetch() API in JS)

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 way they are invoked. when you define a function using onCall e.g.

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

you invoke it on the client side using firebase function client SDK e.g.

// 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 your function using onRequest e.g.

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) e.g.

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