Cloud Function (trigger by HTTP) that would publish a message to PubSub - google-cloud-platform

Question

I am trying to create HTTP API in Cloud Function - that eventually published a message t PubSub. Understood, that there is PubSub REST API - but it enforced me to set up the authentication (in client side) - that I would like to skip and move it to the server side.
Below code is deployed as Google Cloud Function with this command gcloud functions deploy helloGET --runtime nodejs8 --trigger-http
But while tested in browser, it is errored out Error: could not handle the request
Any suggestion is appreciated, thanks!
"use strict";
// [START functions_pubsub_setup]
const { PubSub } = require("#google-cloud/pubsub");
// Instantiates a client
const pubsub = new PubSub();
// [END functions_pubsub_setup]
const Buffer = require("safe-buffer").Buffer;
exports.helloGET = (req, res) => {
const topic = pubsub.topic("projects/myproject/topics/openit");
const message = {
data: {
message: "req.body.message"
}
};
// Publishes a message
res.send(
topic
.publish(message)
.then(() => res.status(200).send("Message published."))
.catch(err => {
err = `Catch block ... ${err}`;
console.error(err);
res.status(500).send(err);
return Promise.reject(err);
})
);
};

Answer 1

Below code will work. But it will take around 30 seconds or plus for the subscriber to receive the event - it is way too slow for my used case :S
"use strict";
const { PubSub } = require("#google-cloud/pubsub");
const pubsub = new PubSub();
const Buffer = require("safe-buffer").Buffer;
exports.helloGET = async (req, res) => {
var toPublish = `hello ${Date.now()}`;
publishMessage("_REPLACE_WITH_TOPIC_NAME_", toPublish);
res.send(`Published ${toPublish}`);
};
async function publishMessage(topicName, data) {
console.log("=> publishMessage, data = ", data);
const dataBuffer = Buffer.from(data);
const topic = pubsub.topic(topicName);
const publisher = topic.publisher();
publisher.publish(dataBuffer, { a: "XYZ" }, function() {
console.log("Published eventually ...");
});
}