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Firebase functions

Information on setting up and deploying Firebase Functions

Firebase functions are not required for initial prototyping of your app, however most projects will need a functions deployment fairly early in the process. Cases where you'll need to deploy functions:

  • Business logic that can't be safely executed in client code.

    • For example, to send push notifications you will need to deploy Firebase Functions
    • This is the most common requirement that leads to your first function deploy

  • To run the admin panel

    • Admin panel authorization falls into the category of "unsafe for client code"

  • Performance of client side data requests

    • Datastore access from the client is handled serially for each "edge hop" (e.g. post -> comment -> author). By deploying on the server you can improve the peformance of these lookups

  • Additional input validation

    • Server-side processing can be used to guarantee invariants when writing data (e.g. text < 50 characters). While Firestore rules have the ability to enforce many patterns, it is difficult to manage these rules and there are invariants that can't be enforced

  • Server-side processing can enhance output when reading data

    • For example, getting a temporary hashed CDN URL for an image

How to deploy

Starting from your app directory:

cd server/functions
yarn firebase use $FIREBASE_PROJECT_ID
yarn firebase deploy --only functions

Notes:

  • Replace $FIREBASE_PROJECT_ID with the ID of your Firebase project

Testing your deployment

To test that functions have successfully deployed, you can write your own Function, or switch the call to getUser to use a server-side function:

  • Go to client/app/AuthConfig.tsx
  • Set CREATE_USERS_ON_SERVER = true

After making this change, when logging in or opening the app after login, a function request will be made to the server. You can verify this request was made either by:

  • On web, viewing the request in the Network tab in Chrome Developer Tools, or
  • Going to the Functions tab in the Firebase console, and viewing request count or logs

How to run Functions locally (in emulator mode)

Download your Firebase credentials

  • Go to the Firebase console
  • Download credentials from Settings icon > Project settings (menu item) > Service accounts (tab) > Generate new private key (button)
  • Save this file in ~/secrets/$PROJECT_NAME.json, where $PROJECT_NAME is the name of your project

Switch app to use emulator mode

  • Go to `common/Firebase.tsx'
  • Set useEmulator: true

Run emulators

cd server/functions
yarn install
sh emulators.sh