Integrating NodeJS with Google Cloud Pub/Sub

Introduction

Google Cloud Pub/Sub is a fully-managed, real-time messaging service that enables you to send and receive messages between independent applications. This article will guide you through integrating NodeJS with Google Cloud Pub/Sub for simple message sending and receiving.

Additionally, I've written an article on using Kafka, a distributed event streaming platform, to demonstrate message sending and receiving through NodeJS and Golang.

Prerequisites

Before proceeding with the following steps, make sure you have:

A Google Cloud account with Pub/Sub enabled.
Basic knowledge of NodeJS. In this article, I'm using a NodeJS TypeScript project. You can find setup instructions here.

Implementing the Code

After setting up your NodeJS TypeScript project, install the following package:

yarn add @google-cloud/pubsub

Next, update the `main.ts` file with the following content:

import {PubSub, Topic, Subscription} from '@google-cloud/pubsub'

export const main = async (): Promise<void> => {
  const projectId = 'project-id', // Google Cloud Platform project ID
    topicName = 'topic-name', // Topic name
    subscriptionName = 'subscription-name' // Subscription name
  const pubsub = new PubSub({projectId})

  const getTopic = async (topicName: string): Promise<Topic> => {
    const topic = pubsub.topic(topicName)
    const [exists] = await topic.exists()
    if (exists) return topic
    
    const [newTopic] = await topic.create()
    return newTopic
  }

  const getSubscription = async (topic: Topic, subscriptionName: string): Promise<Subscription> => {
    const subscription = topic.subscription(subscriptionName)
    const [exists] = await subscription.exists()
    if (exists) return subscription

    const [newSubscription] = await topic.createSubscription(subscriptionName)
    return newSubscription
  }

  const topic = await getTopic(topicName)
  const subscription = await getSubscription(topic, subscriptionName)

  subscription
    .on('message', message => {
      console.log('Received message:', message.data.toString())
    })
    .on('error', error => {
      console.error('Error:', error)
      process.exit(1)
    })

  topic.publishMessage({data: Buffer.from('Message ' + Date.now())})
}

main()

Replace the variables for project ID, topic name, and subscription name to match your setup.
In the `getTopic` and `getSubscription` functions, we've already implemented checks to see if the topic name and subscription name exist. This means you can execute the source code multiple times without encountering errors about the topic or subscription already existing.
The subscription will observe the topic, and when a message is published to the topic, the subscription will log the message content.

When I executed the code, I also published a message to the topic to verify it was working. You can also use the Google Pub/Sub Console to manually publish a message and achieve the same result.