Failed to load function definition from source - functions emulator fails to start or deploy fails

[james-dellow]

[REQUIRED] Environment info

firebase-tools: 12.4.8

Platform: Windows 11 (all updates applied), Node v16.13.0

[REQUIRED] Test case

Sorry, I'm unable to provide an MCVE.

[REQUIRED] Steps to reproduce

Note: This issue is occurring intermittently over the last few days.

Running either firebase deploy or firebase emulators:start results in either the deploy failing or the functions emulators doesn't start, or sometime not all functions are available. Error reported by the CLI is:

!! functions: Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification

However, re-running the command again and it usually works ok on the second attempt.

[REQUIRED] Expected behavior

All functions run in the emulator or the deploy doesn't fail on first attempt.

[REQUIRED] Actual behavior

I've attached the full log for a failed emulator startup, as that's the only one I've been able to capture today, but this may be the relevant section:

[2023-08-21T12:33:42.975Z] > [functions] package.json contents: {
"name": "functions",
"description": "Cloud Functions for Firebase",
"scripts": {
"lint": "eslint .",
"serve": "firebase emulators:start --only functions",
"shell": "firebase functions:shell",
"start": "npm run shell",
"deploy": "firebase deploy --only functions",
"logs": "firebase functions:log"
},
"engines": {
"node": "16"
},
"main": "index.js",
"dependencies": {
"atlassian-jwt": "^2.0.2",
"dayjs": "^1.11.7",
"express-validator": "^6.15.0",
"firebase-admin": "^11.10.1",
"firebase-functions": "^4.4.1",
"nanoid": "^3.3.4",
"node-forge": "^1.3.1"
},
"devDependencies": {
"eslint": "^8.36.0",
"eslint-config-google": "^0.14.0",
"eslint-plugin-promise": "^6.1.1"
},
"private": true
}
[2023-08-21T12:33:42.977Z] Building nodejs source
[2023-08-21T12:33:42.978Z] Failed to find version of module node: reached end of search path C:\Users\MYUSERNAME\documents\my-app\functions\node_modules

• functions: Using node@16 from host.
  [2023-08-21T12:33:42.986Z] Could not find functions.yaml. Must use http discovery
  [2023-08-21T12:33:43.011Z] Found firebase-functions binary at 'C:\Users\MYUSERNAME\documents\my-app\functions\node_modules.bin\firebase-functions'
  Serving at port 8683

shutdown requested via /__/quitquitquit

!! functions: Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification {"metadata":{"emulator":{"name":"functions"},"message":"Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification"}}

debug.txt

[james-dellow]

One other thing I noticed - the process is slow to start when it fails, but when it is successful, both the emulator and deploy start more quickly.

[james-dellow]

While running the emulator today, I encountered the same error:

!! functions: Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification

I immediately re-ran the command and the functions emulator started correctly.

[aalej]

Hi @james-dellow, taking a look into this, it looks like the cause is a network issue based of this log checkFunctionsSDKVersion was unable to fetch information from NPM Error: spawnSync C:\Windows\system32\cmd.exe ETIMEDOUT from the debug.txt you provided. We will work on better surfacing this type of error to make it more visible.

[james-dellow]

Thanks @aalej - is there anything you can suggest that I can do in my environment to mitigate this?

[ErlikC]

I wonder if this has anything to do with #5888.

I'm working with firebase-tools: 13.22.0

In my case I get !! functions: Failed to start functions in C:\Users\MYUSERNAME\documents\my-app: FirebaseError: Failed to load function.

There's an advice to set the environment variable FUNCTIONS_DISCOVERY_TIMEOUT=50, but it only worked for the User code failed to load. Cannot determine backend specification message.

I found that modifying firebase-tools\lib\emulator\functionsRuntimeWorker.js in function waitForSocketReady to something like this, stopped the message. I guess it's taking longer for the socket to be ready.

const timeout = new Promise((resolve, reject) => {
            setTimeout(() => {
                reject(new error_1.FirebaseError("Failed to load function."));
            }, 60000);

Previously it had 30 secs.

It would be great if variable FUNCTIONS_DISCOVERY_TIMEOUT could be added to this spot (of course if that makes sense).