How to publish message in Google Pub/Sub from Firebase Cloud Function?

Question

I wrote a function that receive a http request and send a e-mail. But, I would like receive a http request and send a pub message. The problem is that the documentation is not clear. How I do that?

This is my actual code.

exports.weeklyEmail = functions.https.onRequest((req,res) => {
const email = '****@gmail.com'

console.log('Sending e-mail')

const mailOptions = {
    to: email,
    from: '****@alunos.utfpr.edu.br',
    subject: 'Teste',
    text: 'Conteudo do email '
}   

mailTransport.sendMail(mailOptions).then(
    () => {         
        res.send('Email sent')
    }
).catch(error => {
    res.send(error)
})
})

Answer 1

As I understand, you wish to send a message to Pub/Sub from your Firebase Cloud Functions implementation.

You can easily use the Node.js Pub/Sub client library, with already defined functionalities, like publish.

Or, if you prefer, you can build your own client, directly calling the REST API for Google Cloud Pub/Sub. There's also a RPC reference if it suits your needs better.

---

You won't need

information like host, port, id, passwd of broker

as the mentioned client, or your REST API requests will require authentication .

Answer 2

You need to import pub-sub library const {PubSub} = require('@google-cloud/pubsub'), initiate client, and publish messages.
Docs:

• https://cloud.google.com/pubsub/docs/publisher#publish-messages-to-a-topic
• https://cloud.google.com/functions/docs/calling/pubsub

---

However, One more way is to trigger background function on firestore writes.

whenever you create a doc in a collection (pubsub), your bg function will get invoked on the doc write:

exports.myTriggerFunction = functions.firestore
  .document('pubsub/{docId}')
  .onWrite((change, context) => { /* ... */ });

Also, it's just not limited to onCreate:

Event Type  Trigger
onCreate    Triggered when a document is written to for the first time.
onUpdate    Triggered when a document already exists and has any value changed.
onDelete    Triggered when a document with data is deleted.
onWrite     Triggered when onCreate, onUpdate or onDelete is triggered.