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You can trigger a function in response toRemote Configevents, including
the publication of a new config version or the rollback to an older version.
This guide describes how to create aRemote Configbackground function
that performs a diff of two template versions.
Trigger aRemote Configfunction
To trigger aRemote Configfunction, 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");constlogger=require("firebase-functions/logger");// The Firebase Admin SDK to obtain access tokens.constadmin=require("firebase-admin");constapp=admin.initializeApp();constfetch=require("node-fetch");constjsonDiff=require("json-diff");
# The Cloud Functions for Firebase SDK to set up triggers and logging.fromfirebase_functionsimportremote_config_fn# The Firebase Admin SDK to obtain access tokens.importfirebase_adminapp=firebase_admin.initialize_app()importdeepdiffimportrequests
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 aRemote Configfunction 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 SDKconstaccessTokenObj=awaitadmin.credential.applicationDefault().getAccessToken();constaccessToken=accessTokenObj.access_token;// Get the version number from the event objectconstremoteConfigApi="https://firebaseremoteconfig.googleapis.com/v1/"+`projects/${app.options.projectId}/remoteConfig`;constcurrentVersion=event.data.versionNumber;constprevVersion=currentVersion-1;consttemplatePromises=[];templatePromises.push(fetch(remoteConfigApi,{method:"POST",body:newURLSearchParams([["versionNumber",currentVersion+""]]),headers:{Authorization:"Bearer "+accessToken},},));templatePromises.push(fetch(remoteConfigApi,{method:"POST",body:newURLSearchParams([["versionNumber",prevVersion+""]]),headers:{Authorization:"Bearer "+accessToken},},));// Get the templatesconstresponses=awaitPromise.all(templatePromises);constresults=responses.map((r)=>r.json());constcurrentTemplate=results[0];constpreviousTemplate=results[1];// Figure out the differences of the templatesconstdiff=jsonDiff.diffString(previousTemplate,currentTemplate);// Log the differencelogger.log(diff);}catch(error){logger.error(error);}});
This sample uses thejson-diffandrequest-promisemodules to
create the diff and build the request to get the template object.
Python
@remote_config_fn.on_config_updated()defshowconfigdiff(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 SDKaccess_token=app.credential.get_access_token().access_token# Get the version number from the event objectcurrent_version=int(event.data.version_number)# Figure out the differences between templatesremote_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 differenceprint(diff.pretty())
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-05 UTC."],[],[],null,["\u003cbr /\u003e\n\nYou can trigger a function in response to\nRemote Config events, including\nthe publication of a new config version or the rollback to an older version.\nThis guide describes how to create a Remote Config background function\nthat performs a diff of two template versions.\n\nTrigger a Remote Config function\n\nTo trigger a Remote Config function, first import the\nrequired modules: \n\nNode.js \n\n // The Cloud Functions for Firebase SDK to set up triggers and logging.\n const {onConfigUpdated} = require(\"firebase-functions/v2/remoteConfig\");\n const logger = require(\"firebase-functions/logger\");\n // The Firebase Admin SDK to obtain access tokens.\n const admin = require(\"firebase-admin\");\n const app = admin.initializeApp();\n const fetch = require(\"node-fetch\");\n const jsonDiff = require(\"json-diff\"); \n https://github.com/firebase/functions-samples/blob/c4fde45b65fab584715e786ce3264a6932d996ec/Node/remote-config-diff/functions/index.js#L20-L27\n\nPython \n\n # The Cloud Functions for Firebase SDK to set up triggers and logging.\n from firebase_functions import remote_config_fn\n\n # The Firebase Admin SDK to obtain access tokens.\n import firebase_admin\n\n app = firebase_admin.initialize_app()\n\n import deepdiff\n import requests \n https://github.com/firebase/functions-samples/blob/c4fde45b65fab584715e786ce3264a6932d996ec/Python/remote-config-diff/functions/main.py#L17-L26\n\nThen define a handler for the update event. The event object passed to\nthis function contains metadata\nabout a template update, such as the new version number and time of the update.\nYou can also retrieve the email for the user who made the update, with name\nand an image if available.\n\nHere's an example of a Remote Config function that\nlogs a diff of each updated version and the version it replaced. The function\nexamines the version number field of the template object and retrieves the\ncurrent (newly updated) version together with the version one number lower: \n\nNode.js \n\n exports.showconfigdiff = onConfigUpdated(async (event) =\u003e {\n try {\n // Obtain the access token from the Admin SDK\n const accessTokenObj = await admin.credential.applicationDefault()\n .getAccessToken();\n const accessToken = accessTokenObj.access_token;\n\n // Get the version number from the event object\n const remoteConfigApi = \"https://firebaseremoteconfig.googleapis.com/v1/\" +\n `projects/${app.options.projectId}/remoteConfig`;\n const currentVersion = event.data.versionNumber;\n const prevVersion = currentVersion - 1;\n const templatePromises = [];\n templatePromises.push(fetch(\n remoteConfigApi,\n {\n method: \"POST\",\n body: new URLSearchParams([[\"versionNumber\", currentVersion + \"\"]]),\n headers: {Authorization: \"Bearer \" + accessToken},\n },\n ));\n templatePromises.push(fetch(\n remoteConfigApi,\n {\n method: \"POST\",\n body: new URLSearchParams([[\"versionNumber\", prevVersion + \"\"]]),\n headers: {Authorization: \"Bearer \" + accessToken},\n },\n ));\n\n // Get the templates\n const responses = await Promise.all(templatePromises);\n const results = responses.map((r) =\u003e r.json());\n const currentTemplate = results[0];\n const previousTemplate = results[1];\n // Figure out the differences of the templates\n const diff = jsonDiff.diffString(previousTemplate, currentTemplate);\n // Log the difference\n logger.log(diff);\n } catch (error) {\n logger.error(error);\n }\n }); \n https://github.com/firebase/functions-samples/blob/c4fde45b65fab584715e786ce3264a6932d996ec/Node/remote-config-diff/functions/index.js#L31-L73\n\nThis sample uses the [`json-diff`](https://www.npmjs.com/package/json-diff) and\n[`request-promise`](https://www.npmjs.com/package/request-promise) modules to\ncreate the diff and build the request to get the template object.\n\nPython \n\n @remote_config_fn.on_config_updated()\n def showconfigdiff(event: remote_config_fn.CloudEvent[remote_config_fn.ConfigUpdateData]) -\u003e None:\n \"\"\"Log the diff of the most recent Remote Config template change.\"\"\"\n\n # Obtain an access token from the Admin SDK\n access_token = app.credential.get_access_token().access_token\n\n # Get the version number from the event object\n current_version = int(event.data.version_number)\n\n # Figure out the differences between templates\n remote_config_api = (\"https://firebaseremoteconfig.googleapis.com/v1/\"\n f\"projects/{app.project_id}/remoteConfig\")\n current_template = requests.get(remote_config_api,\n params={\"versionNumber\": current_version},\n headers={\"Authorization\": f\"Bearer {access_token}\"})\n previous_template = requests.get(remote_config_api,\n params={\"versionNumber\": current_version - 1},\n headers={\"Authorization\": f\"Bearer {access_token}\"})\n diff = deepdiff.DeepDiff(previous_template, current_template)\n\n # Log the difference\n print(diff.pretty()) \n https://github.com/firebase/functions-samples/blob/c4fde45b65fab584715e786ce3264a6932d996ec/Python/remote-config-diff/functions/main.py#L31-L53\n\nThis sample uses [`deepdiff`](https://pypi.org/project/deepdiff/) to\ncreate the diff, and `requests` to build and send the request to get\nthe template object."]]
