Setup Google Cloud Pub/Sub for job automation using PHP and Nodejs

In this guide, you will learn how to setup Pub/Sub and use PHP to send messages from one VM Instance and Nodejs to receive messages from another VM Instance and perform any automation tasks

Steps to setup Pub-Sub

1. Create a Pub/Sub Topic
2. Create a Pub/Sub Subscription
3. Create a VM Instance and setup PHP to send messages
4. Create a VM Instance and setup Nodejs to receive messages
5. Test Pub/Sub

Create a Pub/Sub Topic

Go to your Google Cloud Console and navigate to Big Data >> Pub/Sub >> Topics

Click Create Topic

Enter a topic name

Click Create

Create a Pub/Sub Subscription

Once your topic is created click the 3 dots right to your topic and click New Subscription

Enter a subscription name

Click Create

Create a VM Instance and setup PHP to send messages

If you have your instance running you can follow the below steps to install Pub/Sub Client Libraries for PHP else you can follow this tutorial to setup VM Instance in Google Cloud

SSH to your instance and install Composer to install Pub/Sub client libraries

Navigate to your desired directory and run the following command

composer require google/cloud-pubsub

Once the installation is completed you can find the vendor folder and two files composer.json and composer.lock is created

Now we can create a new file and write the code to publish a message to the created Pub/Sub Topic

sudo nano sendmessage.php

Replace YOUR_PROJECT_ID with your Project ID, TOPIC_NAME with your Topic name and MESSAGE with your message and paste the below code to publish a message to the topic

require __DIR__ . '/vendor/autoload.php';
use Google\Cloud\PubSub\PubSubClient;

$pubsub = new PubSubClient([
     'projectId' => 'YOUR_PROJECT_ID',
]);

$topic = $pubsub->topic('TOPIC_NAME');

$topic->publish([
     'data' => 'MESSAGE'
]);

Save the file sendmessage.js

Create a VM Instance and setup Nodejs to receive messages

Create a new instance with Ubuntu 16.10 LTS Boot Image without enabling HTTP and HTTPS Firewall rules because we are not going to use this instance publically instead we are using only for running automation process.

Once you have your instance running proceed to install Nodejs and client libraries for Nodejs

SSH to your new instance and issue the commands one by one

sudo apt update
curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -
sudo apt-get install -y nodejs
sudo apt-get install -y build-essential

Now you have installed Nodejs for listening and ready to make Nodejs listen for incoming messages

mkdir automation
cd automation

sudo nano listener.js

Replace YOUR_PROJECT_ID with your Project ID, SUBSCRIPTION_NAME with your Subscription name paste the below code to receive the messages that are published to Pub/Sub Topic

const PubSub = require('@google-cloud/pubsub');

const pubsub = new PubSub({
     projectId: 'YOUR_PROJECT_ID'
});

const subscription = pubsub.subscription('SUBSCRIPTION_NAME');

let messageCount = 0;
const messageHandler = message => {
     console.log(`Received message ${message.id}:`);
     console.log(`\tData: ${message.data}`);

     messageCount += 1;

     message.ack();
};

subscription.on('message', messageHandler);

setTimeout(() => {
     subscription.removeListener('message', messageHandler);
     console.log(`${messageCount} message(s) received.`);
}, timeout * 1000);

Save the file listener.js

Start Nodejs to listen for new incoming messages

node listener.js

Now your Nodejs app is listening for incoming messages. Keep the SSH open to check for incoming messages

Testing Pub/Sub

Go to your PHP installed instance and edit the sendmessage.php file and replace the MESSAGE with your message and run the following command

php sendmessage.php

Now you will receive the message in the Nodejs installed instance.