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My application makes use of Firestore Function Triggers to perform background actions based on changes in the Firestore, e.g. user profile changes. For example, if they change their mobile number, a verification code is sent.

I have a trigger that should run when an onWrite() event happens on a specific collection. onWrite() runs when any of the following actions occur in Firebase on a specific collection:

In my usecase, I need it to run for onCreate() and onUpdate(), thus I use onWrite()

For Firebase Triggers to work, a specific format is expected in addition to a document id/wildcard representing a document that was created/changed/deleted.

Constants:

const collections = {
    ...
    conversations: "conversations",
    ...
}

Callable Function (updates firestore):

/**
 * Add an conversation to conversations collection
 * @type {HttpsFunction & Runnable<any>}
 */
exports.addConversations = functions.https.onCall(async (data, context) =>  {
    // expects conversation & interested state
    const {valid, errors} = validateRequiredBody(data, [
        "conversation",
    ]);
    if (!valid) {
        return {
            status: false,
            message: "Missing or invalid parameters",
            errors: errors,
            jwtToken: "",
        };
    }

    // get conversation item
    const conversation = {
        id: data["conversation"]["id"],
        name: data["conversation"]["name"],
    }

    // create conversation with empty counter
    // let writeResult = await collectionRefs.conversationsRef.doc(conversation.id).set({
    let writeResult = await admin.firestore().collection(collections.conversations).doc(conversation.id).set({
        id: conversation.id,
        name: conversation.name,
        count: 0
    });
    console.log(`[function-addConversations] New Conversation [${conversation.name}] added`);

    return {
        status: true,
        message: ""
    }
});

Firestore Trigger (not triggering):

/**
 * On conversations updated/removed, update corresponding counter
 * @type {CloudFunction<Change<QueryDocumentSnapshot>>}
 */
exports.onConversationProfileCollectionCreate = functions.firestore.document(`${collections.conversations}/{id}`)
    .onWrite(async snapshot => {
        console.log("Conversation Collection Changed");
        // let conversation = collectionRefs.conversationsRef.doc(snapshot.id);
        // await conversation.update({count: FieldValue.increment(1)});
    });

In my mobile application, the user (calls) the addConversations() firebase function, this adds the new conversation to Firestore which is clearly visible, but the counter trigger (trigger function) doesn't run.

Emulator output:

...
{"verifications":{"app":"MISSING","auth":"MISSING"},"logging.googleapis.com/labels":{"firebase-log-type":"callable-request-verification"},"severity":"INFO","message":"Callable request verification passed"}
[function-addConversations] New Conversation [Test Conversation Topic] added
Profile updated 
(print profile data)
...

What I SHOULD expect to see:

...
{"verifications":{"app":"MISSING","auth":"MISSING"},"logging.googleapis.com/labels":{"firebase-log-type":"callable-request-verification"},"severity":"INFO","message":"Callable request verification passed"}
[function-addConversations] New Conversation [Test Conversation Topic] added
Conversation Collection Changed      // this is output by the trigger
Profile updated 
(print profile data)
...

Did I do something wrong?

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12
  • Do you see anything from the function execution in the log? E.g. onConversationProfileCollectionCreate Function execution started Commented Jul 2, 2021 at 9:24
  • Hi @RenaudTarnec no. I have a profile onWrite() trigger that outputs Profile Updated, but nothing else in the standard terminal output. Do you have a suggestion how I can enable verbose logging? Commented Jul 2, 2021 at 10:06
  • What happens if you try to deploy the Cloud Functions? Commented Jul 2, 2021 at 11:21
  • Maybe the collection name is being declared improperly or something. Have you checked if ${collections.conversations} has the value you expect it to have? Also, are there any errors popping in the firebase-debug.log? Commented Jul 2, 2021 at 12:38
  • 2
    When you tested this on your system, did you make sure that your Cloud Functions were writing to the emulators and not your live database? Commented Jul 25, 2021 at 5:24

2 Answers 2

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1

The issue was one closer to home.

I am developing using the firebase emulators and connecting to them using the emulators addition in Flutter's firebase packages built in emulator feature.

Firebase emulator setup e.g. Firebase Functions can be found here

TL;DR:

When starting your Firebase emulator, you should see something similar to:

C:\Users\User\MyApp\awesome-app-server>firebase emulators:start --only functions
i  emulators: Starting emulators: functions
!  functions: You are running the functions emulator in debug mode (port=9229). This means that functions will execute in sequence rather than in parallel.
!  functions: The following emulators are not running, calls to these services from the Functions emulator will affect production: auth, firestore, database, hosting, pubsub, storage
!  Your requested "node" version "12" doesn''t match your global version "14"
i  ui: Emulator UI logging to ui-debug.log
i  functions: Watching "C:\Users\User\MyApp\awesome-app-server\functions" for Cloud Functions...
>  Debugger listening on ws://localhost:9229/03dc1d62-f2a3-418e-a343-bb0b357f7329
>  Debugger listening on ws://localhost:9229/03dc1d62-f2a3-418e-a343-bb0b357f7329
>  For help, see: https://nodejs.org/en/docs/inspector
!  functions: The Cloud Firestore emulator is not running, so calls to Firestore will affect production.
!  functions: The Realtime Database emulator is not running, so calls to Realtime Database will affect production.

...

BUT then you see this - THIS is very important!

i  functions[us-central1-api-user-onConversationProfileCollectionCreate ]: function ignored because the database emulator does not exist or is not running.

This, since Firestore & (Realtime) Database use triggers which are found in functions, functions expects to find a local firestore/database emulator.

Since no firestore/database emulators were running locally

!  functions: The Cloud Firestore emulator is not running, so calls to Firestore will affect production.
!  functions: The Realtime Database emulator is not running, so calls to Realtime Database will affect production.

and these functions don't automagically attach to production Firestore/Database(s) (that would be potentially devestating), these triggers didn't run when I expected them to while emulating locally.

Solution:

  1. Emulate firestore & database locally (see this to import your firestore data to a local emulator) with firebase emulators:start --only functions,...,firestore,database

  2. Upload functions to work with Firestore/Database(s) (please do this with care)

More details:

Below I provide details what lead me to the problem, and how I figured out the issue:

What I was doing:

firebase emulators:start --inspect-functions --only functions,auth
  • [local] Firebase Functions I was developing and testing the backend for my mobile app using Firebase Functions for various interactivity.
  • Since Firebase Auth is handled locally through the use of custom tokens on my firebase functions app, I used local auth for testing

I had prepopulated my Firestore with data, thus I intended to use Firestore data while emulating locally which had worked as expected, BUT the firebase firestore & database triggers won't work due to emulating them locally.

I knew some of my triggers DID infact trigger correctly, thus it must be a configuration error of some kind.

Extended Solution (import firestore data to local emulator)

firebase emulators:start --inspect-functions --only functions,auth,firestore,database

notice the last 2, firestore & database - this should be added for triggers to work locally

  • I noticed when reviewing the logs at startup, the text indicating some functions won't run. This made me realize I was making a crucial mistake - the cause.

Import Data from production firestore

The reason for using production (during development) firestore is to not recreate all the data for each test. The solution is to export from firestore and import you data to the emulators.

See this for details - I wasn't able to export from the terminal, I thus went to Google Console to export to a storage bucket, and download it via the console from there.

To start the emulator (and allow debugging of firebase functions), I use:

firebase emulators:start --inspect-functions --import ./functions/{path/to/data} --only functions,auth,firestore,database

details:

  • firebase emulators:start - start emulator
  • --inspect-functions allow debugging functions via websockets - e.g. Webstorm NodeJs debugger on port 9229
  • --import ./functions/{path/to/data} - import data to firestore emulator using project root as ./
  • --only functions,auth,firestore,database specify the modules to emulate
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Comments

0

You are using the wrong value. snapshot works only for onDelete and onCreate method 

exports.useWildcard = functions.firestore
    .document('users/{userId}')
    .onWrite((change, context) => {
      // If we set `/users/marie` to {name: "Marie"} then
       context.params.userId == "marie"
      // ... and ...
      change.after.data() == {name: "Marie"}
    });

for more info read here feedbackCloud Firestore triggers

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3 Comments

From a firebase example: firebase.google.com/docs/functions/…
I added the link. That is why I said "for more info read here"
ah - I see the confusion. snapshot in the context of .onWrite(async snapshot => { can cause confusion, but this is fundamentally just a variable name such as context, change, etc. This was not the underlying cause/reason for it no to work - your suggestion is merely aesthetics. See my posted answer for the cause and solution.

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