Event Notification

1. What exactly is Event Notification?

A WebJob runs every 5 minutes. Each time, it looks inside Azure Blob Storage for any file that hasn't been processed yet, and starts on it.

A file that finishes uploading right after a run has to sit and wait, up to 5 minutes, before anyone even looks at it. And most of those 5-minute windows pass with no new upload at all, so most runs find nothing waiting for them.

A fresh upload sits idle until the next scheduled run gets to it, and most runs turn up nothing at all. That's exactly what event notification fixes.

2. How would you fix it in Azure?

Event notification skips the waiting entirely: configure Azure Blob Storage to publish an event to Azure Event Grid the moment a new file is created, and subscribe an Azure Function to that event using an EventGridTrigger binding. The Azure Function runs the moment the event arrives, instead of a WebJob having to go looking for the file.

Use: Azure Event Grid (EventGridTrigger)

React to the event when it happens, instead of asking repeatedly whether it happened yet.

3. How can you visualize it in everyday terms?

A doorbell rings the instant someone is at the door.

Without one, you'd have to walk over and check every few minutes, mostly finding no one there, and whoever arrived right after your last check still has to wait for your next one.

Something rings the moment it happens, instead of you walking over to check.