II. Getting Started

Key Concepts

1. Async Events: are events that are dispatched from Magento when they are triggered
2. Subscribers: is something that listens to one or several async events.

Defining an Async Event

Async events are defined in etc/async_events.xml. The definition only provides an acknowledgement to Magento that such an async event exists. It has to be dispatched by you at a place you find suitable.

    <async_event name="sales.order.created">
        <service class="Magento\Sales\Api\OrderRepositoryInterface" method="get"/>
    </async_event>

1. async_event
   • name - A unique name given to the asynchronous event
2. service
   • class - The class or interface that defines the handler.
   • method - The method which is executed and the return value is published to subscribers.

Dispatching Async Events

Events are dispatched by simply publishing to the EVENT_QUEUE using the Magento\Framework\MessageQueue\PublisherInterface, however it needs to follow a certain structure.

The Magento\Framework\MessageQueue\PublisherInterface::publish takes in two arguments

public function publish($topicName, $data);

The first argument $topicName SHOULD be a string that's defined by the constant \Aligent\AsyncEvents\Helper\QueueMetadataInterface::EVENT_QUEUE

The second argument $data follows a specific structure. It should contain an array of two strings.

1. The first string specifies what async_event to dispatch. (anything that's defined in async_events.xml)
2. The second string SHOUD be a JSON serialised string. The serialised string should contain the named arguments of the service method that resolves the async event.

For example, if your service method was Magento\Sales\Api\OrderRepositoryInterface::get which takes in the following inputs

/**
 * @param int $id The order ID.
 * @return \Magento\Sales\Api\Data\OrderInterface Order interface.
 */
public function get($id);

your $data array should look like

$arguments = ['id' => $orderId];
$data = ['sales.order.created', $this->json->serialize($arguments)]

This is likely to change in a future major version where a AsyncEventMessageInterface would be passed instead of an array of two strings.

Example:

    public function execute(Observer $observer): void
    {
        /** @var Order $object */
        $object = $observer->getEvent()->getData('order');

        $arguments = ['id' => $object->getId()];
        $data = ['sales.order.created', $this->json->serialize($arguments)];

        $this->publisher->publish(QueueMetadataInterface::EVENT_QUEUE, $data);
    }

Notifiers

Each subscription might want to be handled a little differently. This is useful when each subscriber has their own preferred way of receiving notifications.

Creating Subscriptions

Finally, to receive notifications of async events, you have to create subscribers. The module has a REST API to create and manage subscriptions.

{
    "asyncEvent": {
        "event_name": "sales.order.created",
        "recipient_url": "https://example.com/order_created",
        "verification_token": "fv38u07Wdh$R@mRd",
        "metadata": "http"
    }
}