Remote Config triggers

You can trigger a function in response to Firebase Remote Config events, including the publication of a new config version or the rollback to an older version. This guide describes how to create a Remote Config background function that performs a diff of two template versions.

Trigger a Remote Config function

To trigger a Remote Config function, first import the required modules:

Node.js

 // The Cloud Functions for Firebase SDK to set up triggers and logging.
const {onConfigUpdated} = require("firebase-functions/v2/remoteConfig");
const logger = require("firebase-functions/logger");
// The Firebase Admin SDK to obtain access tokens.
const admin = require("firebase-admin");
const app = admin.initializeApp();
const fetch = require("node-fetch");
const jsonDiff = require("json-diff");
index.js

Python

 # The Cloud Functions for Firebase SDK to set up triggers and logging.
from firebase_functions import remote_config_fn

# The Firebase Admin SDK to obtain access tokens.
import firebase_admin

app = firebase_admin.initialize_app()

import deepdiff
import requests
main.py

Then define a handler for the update event. The event object passed to this function contains metadata about a template update, such as the new version number and time of the update. You can also retrieve the email for the user who made the update, with name and an image if available.

Here's an example of a Remote Config function that logs a diff of each updated version and the version it replaced. The function examines the version number field of the template object and retrieves the current (newly updated) version together with the version one number lower:

Node.js

 exports.showconfigdiff = onConfigUpdated(async (event) => {
  try {
    // Obtain the access token from the Admin SDK
    const accessTokenObj = await admin.credential.applicationDefault()
        .getAccessToken();
    const accessToken = accessTokenObj.access_token;

    // Get the version number from the event object
    const remoteConfigApi = "https://firebaseremoteconfig.googleapis.com/v1/" +
        `projects/${app.options.projectId}/remoteConfig`;
    const currentVersion = event.data.versionNumber;
    const prevVersion = currentVersion - 1;
    const templatePromises = [];
    templatePromises.push(fetch(
        remoteConfigApi,
        {
          method: "POST",
          body: new URLSearchParams([["versionNumber", currentVersion + ""]]),
          headers: {Authorization: "Bearer " + accessToken},
        },
    ));
    templatePromises.push(fetch(
        remoteConfigApi,
        {
          method: "POST",
          body: new URLSearchParams([["versionNumber", prevVersion + ""]]),
          headers: {Authorization: "Bearer " + accessToken},
        },
    ));

    // Get the templates
    const responses = await Promise.all(templatePromises);
    const results = responses.map((r) => r.json());
    const currentTemplate = results[0];
    const previousTemplate = results[1];
    // Figure out the differences of the templates
    const diff = jsonDiff.diffString(previousTemplate, currentTemplate);
    // Log the difference
    logger.log(diff);
  } catch (error) {
    logger.error(error);
  }
});
index.js

This sample uses the json-diff and request-promise modules to create the diff and build the request to get the template object.

Python

 @remote_config_fn.on_config_updated()
def showconfigdiff(event: remote_config_fn.CloudEvent[remote_config_fn.ConfigUpdateData]) -> None:
    """Log the diff of the most recent Remote Config template change."""

    # Obtain an access token from the Admin SDK
    access_token = app.credential.get_access_token().access_token

    # Get the version number from the event object
    current_version = int(event.data.version_number)

    # Figure out the differences between templates
    remote_config_api = ("https://firebaseremoteconfig.googleapis.com/v1/"
                         f"projects/{app.project_id}/remoteConfig")
    current_template = requests.get(remote_config_api,
                                    params={"versionNumber": current_version},
                                    headers={"Authorization": f"Bearer {access_token}"})
    previous_template = requests.get(remote_config_api,
                                     params={"versionNumber": current_version - 1},
                                     headers={"Authorization": f"Bearer {access_token}"})
    diff = deepdiff.DeepDiff(previous_template, current_template)

    # Log the difference
    print(diff.pretty())
main.py

This sample uses deepdiff to create the diff, and requests to build and send the request to get the template object.