Debugging Firebase functions locally (node.js)

Question

see below my code is very simple....it listens to a change on a database field in realtime-database.

const functions = require("firebase-functions");
var admin = require("firebase-admin");

exports.onActiveUpdate = functions.database
  .ref("/profiles/users/{userId}/active")
  .onUpdate((change, context) => {
      //code here
      
    return true;
  });

I've tried to debug code locally with the following commands

firebase serve --only functions
firebase serve
firebase emulators:start

I always get the same message...

+  functions: Emulator started at http://localhost:5001
i  functions: Watching "C:\code\rn\xs\fb_functions\functions" for Cloud Functions...
i  functions[onActiveUpdate]: function ignored because the database emulator does not exist or is not running.
+  All emulators started, it is now safe to connect.

But then when I go to localhost:5001....all I see is a blank page with with {"status":"alive"} at the top.

Is this correct behavior? Thanks

Answer 1

You can run the emulator in inspect mode by running :

firebase emulators:start --inspect-functions

See what port it's listening to for debug (e.g. port 9229 ). If you are using VSCode, create(or update) a launch.json inside .vscode subdirectory of your project with the following content:

   {
    "configurations": [
        {   "type": "node",
            "request": "attach",
            "name": "Debug",
            "port": 9229
        }
     ]
   }

Then simply click on Debug icon in your VScode to connect to the running process. Now put some breakpoints in your functions code and invoke them through browser.

Answer 2

You can use https://github.com/GoogleChromeLabs/ndb to debug your http firebase functions.

Install it locally or globally and run your normal serve command with ndb:

ndb yarn serve