Event routing, filtering, and system Events

1. Event routing, filtering, and system Events

In this video, you’ll explore how event routing works, how to filter events in Azure Event Grid, and, finally, what system events are. We will use MQTT as an example.

2. MQTT overview

Let’s start with Message Queuing Telemetry Transport (MQTT). Imagine an Internet of Things setup where multiple devices, like weather stations, continuously send measurements such as temperature and humidity. MQTT enables communication between these devices and the server. It’s designed for low-bandwidth, high-latency, or unreliable network - the kind you often get with sensors placed outdoors or in obscure locations.

3. Event filtering

Now, let's talk about filtering. When Azure IoT Hub emits telemetry for many sensors, you might only want to process specific data. For example, you may care only about temperature readings from a particular device and ignore everything else. You can achieve this by applying filters when you create your Azure Event Grid subscription.

4. Event filtering in Event Grid

Event Grid provides powerful filtering so only relevant events reach subscribers. You can filter by subject, event type, or properties within the event data. For example, if your system processes many different types of media, you may set a filter for image-processing service that looks only for JPEG or PNG files and ignores everything else. Advanced filters allow comparisons like "greater than" or checks like "contains", giving you granular control over what your subscribers can handle.

5. Event routing

Next, event routing. How do you decide where the sensor data goes? Event Grid uses a publish-subscribe model. Event sources, such as Azure IoT Hub, publish events to Event Grid topics. Subscriptions then define the destinations, ensuring each message reaches the right place, whether that’s a data processing pipeline, an Azure Function, or a storage system. Without event routing, you won't be able to work with MQTT and receive IoT device data.

6. System events

Finally, system events. These are predefined events emitted by Azure services, which makes building event-driven applications easier. For example, Azure Storage emits events like BlobCreated and BlobDeleted. IoT Hub emits device lifecycle events, such as when a device connects or disconnects. Event Grid automatically creates system topics for these services. You don’t have to manage those topics yourself. You simply subscribe to the events you’re interested in.

7. Event grid is key in filtering events

To recap: MQTT helps your IoT telemetry reach the cloud reliably. Event Grid’s filtering lets you control exactly which events are processed. And system events let you integrate seamlessly with Azure services.

8. Let's practice!

Now, let’s practice.

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