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Use Firestore with Cloud Functions

Author(s): @zeroasterisk ,   Published: 2018-12-29

Alan Blount | Product Solutions Engineer | Google

Contributed by Google employees.

This tutorial demonstrates using Cloud Functions to store and retrieve data with Firestore. The Cloud Function is implemented in Node.js version 6 or 8.

The sample Cloud Function is triggered by a web request, which you can simulate with curl.


  1. Create a project in the Cloud Console.
  2. Enable billing for your project.
  3. Enable the Cloud Functions API.
  4. Enable the Firestore API (with Firestore in Native mode).
  5. Install and initialize the Cloud SDK.
  6. Configure the gcloud command-line interface for your project, replacing [PROJECT_ID] with your project ID:

    gcloud config set project [PROJECT_ID]

This guide uses cloud-functions-firestore as the project ID, as well as the firestore collection.

Preparing the Cloud Function

This Cloud Function will either store a basic POST payload as a document in Firestore or retrieve a document from Firestore by ID.

You can find the
[zerobin codebase on github](...)
which is the source of this example.

Alternatively, you can download package.json & index.js

Start a new npm app

If you do not already have an npm project, go ahead and create one in a new directory:

npm init

Install @google-cloud/firestore

Let's add the Firestore client to our Node.js app, saving the dependency.

npm install --save --save-exact @google-cloud/firestore

Writing the Cloud Function code

You can copy and paste the simplified version of the code, into index.js (or download).

const Firestore = require('@google-cloud/firestore');
const PROJECTID = 'cloud-functions-firestore';
const COLLECTION_NAME = 'cloud-functions-firestore';
const firestore = new Firestore({
  projectId: PROJECTID,
  timestampsInSnapshots: true,

exports.main = (req, res) => {
  if (req.method === 'DELETE') throw 'not yet built';
  if (req.method === 'POST') {
    // store/insert a new document
    const data = (req.body) || {};
    const ttl = Number.parseInt(data.ttl);
    const ciphertext = (data.ciphertext || '').replace(/[^a-zA-Z0-9\-]*/g, '');
    const created = new Date().getTime();
    return firestore.collection(COLLECTION_NAME)
      .add({ created, ttl, ciphertext })
      .then(doc => {
        return res.status(200).send(doc);
      }).catch(err => {
        return res.status(404).send({ error: 'unable to store', err });
  // read/retrieve an existing document by id
  if (!(req.query && req.query.id)) {
    return res.status(404).send({ error: 'No Id' });
  const id = req.query.id.replace(/[^a-zA-Z0-9]/g, '').trim();
  if (!(id && id.length)) {
    return res.status(404).send({ error: 'Empty Id' });
  return firestore.collection(COLLECTION_NAME)
    .then(doc => {
      if (!(doc && doc.exists)) {
        return res.status(404).send({ error: 'Unable to find the document' });
      const data = doc.data();
      return res.status(200).send(data);
    }).catch(err => {
      return res.status(404).send({ error: 'Unable to retrieve the document' });

In that code, the function is going to listen for a POST with the data fields of ciphertext and ttl. It will store the values into a new document in firestore using the add() function (which auto-assigns an ID).

And the function is also listening for a GET request with an id in the querystring. It will lookup that document in firestore and, if found, return the document.

Note: You probably want more input sanitation for a production application.

Deploying the Cloud Function

Once the code is deployed, Cloud Functions will automatically run that code for us, when triggered.

You now have a package.json file listing your dependencies and you have an index.js file which will respond to an HTTP trigger.

You will use the gcloud command-line tool to deploy our function, and configure it to listen to HTTP requests.

(optional) Install functions-emulator for local testing

Testing things is nice. You can install a local emulator for Cloud Functions.

npm install -g @google-cloud/functions-emulator
export GOOGLE_APPLICATION_CREDENTIALS=/Users/myname/.cred/myserviceaccount.json
functions start
functions deploy main --trigger-http --runtime=nodejs10

In this case, main is the name of the function you want to trigger in your code, triggered by an HTTP request.

Note: If you're on zsh, you may not be able to execute functions. Either start bash, or execute sh -c 'which functions' to find the proper path for you. For example: /Users/myname/.npm-global/bin/functions

Now you can test your function by sending curl requests.

You can create a new document:

curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"ttl":1,"ciphertext":"daa5370871aa301e5e12d4274d80691f75e295d648aa84b73e291d8c82"}' \

And retrieve that document:

curl http://localhost:8010/cloud-functions-firestore/us-central1/main?id=wLcIOzic6BeoEk3tV4sH

Note that our function code added created.

Deploy the code to Google Cloud Functions

This is very easy thanks to the gcloud command-line interface.

gcloud functions deploy main --trigger-http --runtime=nodejs10

In this case, main is the name of the function you want to trigger in your code, triggered by an HTTP request.

If you used the emulator above, you can simply prefix the command with gcloud.

Deploying function (may take a while - up to 2 minutes)...done.
availableMemoryMb: 256
entryPoint: main
  url: https://us-central1-cloud-functions-firestore.cloudfunctions.net/main
  deployment-tool: cli-gcloud
name: projects/cloud-functions-firestore/locations/us-central1/functions/main
runtime: nodejs10
serviceAccountEmail: cloud-functions-firestore@appspot.gserviceaccount.com
sourceUploadUrl: https://storage.googleapis.com/gcf-upload-us-central1-0000000000.zip?GoogleAccessId=service-...
status: ACTIVE
timeout: 60s
updateTime: '2018-09-15T01:25:59Z'
versionId: '1'

Testing the deployed Cloud Function in production

You should now be able to send HTTP requests to the endpoint and test out the function in production.

Now you can test your function by sending curl requests.

You can create a new document:

curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"ttl":1,"ciphertext":"daa5370871aa301e5e12d4274d80691f75e295d648aa84b73e291d8c82"}' \

And retrieve that document:

curl https://us-central1-cloud-functions-firestore.cloudfunctions.net/main?id=wLcIOzic6BeoEk3tV4sH

Note that our function code added created.


This is a very short cycle of [code, deploy, test] so you should be able to iterate rapidly.

When you deploy, you overwrite the current version, at the function's URL (blue/green deployment in the background, can take a few seconds to switch over).

If you need to access a previously deployed version, you can append /revisions/${REVISION} with the value of the versionId that deploy gives you back.

There are lot of other settings available. Review docs and help:

 gcloud functions deploy --help

Your turn

As you can see, it is very easy to create and deploy small functions.

You can deploy larger applications just as easily.

Your functions can be triggered by many other events, not just web requests.

And you only pay for your functions for the seconds they are being run, and they can scale out as needed even if you get super-popular.

Read more about functions and make something awesome!

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