Install the RabbitMQ on Ubuntu by using below command.

sudo apt install -y rabbitmq-server

Install Magento with RabbitMQ. And connect to Magento Open Source or Magento Commerce.

--amqp-host="<hostname>" --amqp-port="5672" --amqp-user="<user_name>" --amqp-password="<password>" --amqp-virtualhost="/"

Connect RabbitMQ

If you already had Magento installed and you want to connect it to RabbitMQ, add a queue section in the <install_directory>/app/etc/env.php file

'queue' =>
  array (
    'amqp' =>
    array (
      'host' => 'localhost',
      'port' => '5672',
      'user' => 'example',
      'password' => 'example',
      'virtualhost' => '/'
     ),
  ),

Then, run bin/magento setup:upgrade to apply the changes & create the required queues in RabbitMQ.

To enable RabbitMQ:

Add the required name, type, and disk value (in MB) to the .magento/services.yaml file along with the installed RabbitMQ version.

rabbitmq:
    type: rabbitmq:<version>
    disk: 1024

Configure the relationships in the .magento.app.yaml file.

relationships:
    rabbitmq: "rabbitmq:rabbitmq"

Add, commit, and push your code changes.

git add -A
git commit -m "Enable RabbitMQ service"
git push origin <branch-name>

Verify the service relationships.

Retrieve the RabbitMQ connection details :

php -r 'print_r(json_decode(base64_decode($_ENV["MAGENTO_CLOUD_RELATIONSHIPS"])));'