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Architecture Overview

This document gives an overview of the notification architecture and how it works.

Introduction

Medusa provides a Notification API to mainly handle sending and resending notifications when an event occurs. For example, sending an email to the customer when they place an order.

The Notification architecture is made up of 2 main components: the Notification Provider and the Notification. Simply put, the Notification Provider handles the sending and resending of a Notification.

Notification Provider

A Notification Provider is a provider that handles sending and resending of notifications. You can either create and integrate your own provider or install a Notification Provider through a third-party plugin.

An example of a notification provider is SendGrid. When an order is placed, the SendGrid plugin sends an email to the customer.

How Notification Provider is Created

A Notification Provider is essentially a Medusa Service with a unique identifier, and it extends the NotificationService provided by the medusa-interfaces package. It can be created as part of a Plugin, or it can be created just as a Service file in your Medusa server.

As a developer, you mainly work with the Notification Provider when integrating a third-party service that handles notifications in Medusa.

When you run your Medusa server, the Notification Provider is registered on your server if it isn’t already. This means that it will be inserted into the notification_provider table in your database.

NotificationProvider Entity Overview

The NotificationProvider entity only has 2 attributes: id and is_installed.

id is the value of the static property identifier defined inside the notification Service class.

is_installed indicates whether the Notification Provider is installed or not. When you install a Notification Provider, the value of this attribute is true.

If you installed a Notification provider and then removed the Service files or plugin that registered the Notification Provider, the Notification Provider remains in your database, but the value of the is_installed field changes to false.

Notification

A notification is a form of an alert sent to the customers or users to inform them of an action that has occurred. For example, if an order is placed, the notification, in this case, can be an email that confirms their order and lists the order details.

Notifications can take on other forms such as an SMS or a Slack message.

How Notification is Created

Notifications are created in the NotificationService class in Medusa’s core after the Notification has been handled by the Notification Provider.

The data and additional details that the Notification Provider returns to the NotificationService is used to fill some of the attributes of the Notification in the database.

A Notification also represents a resent notification. So, when a notification is resent, a new one is created that references the original Notification as a parent. This Notification is also created by the NotificationService class.

Notification Entity Overview

The 2 most important properties in the Notification entity are the to and data properties.

The to property is a string that represents the receiver of the Notification. For example, if the Notification was sent to an email address, the to property holds the email address the Notification was sent to.

The to property can alternatively be a phone number or a chat username. It depends on the Notification Provider and how it sends the Notification.

The data property is an object that holds all the data necessary to send the Notification. For example, in the case of an order confirmation Notification, it can hold data related to the order.

The data property is useful when a notification is resent later. The same data can be used to resend the notification.

In the case of resent notifications, the resent notification has a parent_id set to the ID of the original Notification. The value of the parent_id property in the original Notification is null.

The Notification entity has some properties that determine the context of this Notification. This includes the event_name property which is the event that triggered the sending of this notification.

Additionally, the resource_type property is used to determine what resource this event is associated with. For example, if the event_name is order.placed, the resource_type is order.

You can also access the specific resource using the resource_id property, which is the ID of the resource. So, in case of the order.placed event, the resource_id is the ID of the order that was created.

The Notification entity also includes properties related to the receiver of the Notification. In case the receiver is a customer, the customer_id property is used to identify which customer.

Automating Flows with Notifications

With Medusa you can create notifications as a reaction to a wide spectrum of events, allowing you to automate communication and processes.

An example of a flow that can be implemented using Medusa's Notification API is automated return flows:

  • A customer requests a return by sending a POST request to the /store/returns endpoint.
  • The Notification Provider listens to the order.return_requested event and sends an email to the customer with a return invoice and return label generated by the Fulfillment Provider.
  • The customer returns the items triggering the return.recieved event.
  • The Notification Provider listens to the return.received event and sends an email to the customer with confirmation that their items have been received and that a refund has been issued.

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