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Event Grid subscriptions and filters in Azure - Commands & Configuration

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Introduction

Event Grid subscriptions let you receive notifications when something happens in your cloud resources. Filters help you choose which events you want to get, so you only get the important ones.

When you want to get notified only about new files added to a storage container, not all changes.

When you want to trigger a function only if a virtual machine changes state to running.

When you want to send alerts only for error events from your app, ignoring info messages.

When you want to connect your app to events from multiple sources but only care about specific event types.

When you want to reduce the amount of data your app processes by filtering events early.

Config File - eventgrid-subscription.json

eventgrid-subscription.json

{
  "type": "Microsoft.EventGrid/eventSubscriptions",
  "apiVersion": "2023-06-01",
  "name": "myEventSubscription",
  "properties": {
    "destination": {
      "endpointType": "WebHook",
      "properties": {
        "endpointUrl": "https://myapp.example.com/api/events"
      }
    },
    "filter": {
      "subjectBeginsWith": "/blobServices/default/containers/images/",
      "subjectEndsWith": ".jpg",
      "isSubjectCaseSensitive": false,
      "includedEventTypes": [
        "Microsoft.Storage.BlobCreated"
      ]
    }
  }
}

This JSON creates an Event Grid subscription named myEventSubscription.

The destination is a webhook URL where events will be sent.

The filter section limits events to those where the subject starts with /blobServices/default/containers/images/ and ends with .jpg, meaning only new JPEG images in the images container.

It also only includes the event type Microsoft.Storage.BlobCreated, so only new blobs trigger the subscription.

The filter is case insensitive for the subject.

Commands

This command creates an Event Grid subscription named myEventSubscription. It listens to blob created events from the storage account mystorageaccount. It filters events to only those starting with the images container path and ending with .jpg files. Events are sent to the specified webhook endpoint.

Terminal

az eventgrid event-subscription create --name myEventSubscription --source-resource-id /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount --endpoint https://myapp.example.com/api/events --included-event-types Microsoft.Storage.BlobCreated --subject-begins-with /blobServices/default/containers/images/ --subject-ends-with .jpg

Expected OutputExpected

{ "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/providers/Microsoft.EventGrid/eventSubscriptions/myEventSubscription", "name": "myEventSubscription", "type": "Microsoft.EventGrid/eventSubscriptions", "destination": { "endpointType": "WebHook", "properties": { "endpointUrl": "https://myapp.example.com/api/events" } }, "filter": { "includedEventTypes": [ "Microsoft.Storage.BlobCreated" ], "subjectBeginsWith": "/blobServices/default/containers/images/", "subjectEndsWith": ".jpg", "isSubjectCaseSensitive": false }, "provisioningState": "Succeeded" }

→

--included-event-types - Specifies which event types to receive

→

--subject-begins-with - Filters events by subject prefix

→

--subject-ends-with - Filters events by subject suffix

This command shows the details of the event subscription named myEventSubscription to verify it was created with the correct filters and destination.

Terminal

az eventgrid event-subscription show --name myEventSubscription --source-resource-id /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount

Expected OutputExpected

This command lists all event subscriptions on the storage account to see all active subscriptions and their filters.

Terminal

az eventgrid event-subscription list --source-resource-id /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount

Expected OutputExpected

[ { "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount/providers/Microsoft.EventGrid/eventSubscriptions/myEventSubscription", "name": "myEventSubscription", "destination": { "endpointType": "WebHook", "properties": { "endpointUrl": "https://myapp.example.com/api/events" } }, "filter": { "includedEventTypes": [ "Microsoft.Storage.BlobCreated" ], "subjectBeginsWith": "/blobServices/default/containers/images/", "subjectEndsWith": ".jpg", "isSubjectCaseSensitive": false }, "provisioningState": "Succeeded" } ]

This command deletes the event subscription named myEventSubscription when it is no longer needed to stop receiving events.

Terminal

az eventgrid event-subscription delete --name myEventSubscription --source-resource-id /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Storage/storageAccounts/mystorageaccount

Expected OutputExpected

No output (command runs silently)

Key Concept

If you remember nothing else from this pattern, remember: filters let you receive only the events you care about, saving time and resources.

Common Mistakes

Not specifying included event types when creating the subscription

You might receive all event types, causing unnecessary processing and noise.

Always use the --included-event-types flag to limit events to only those you want.

Using incorrect subject filters that do not match event subjects

No events will be delivered because the filter excludes all events.

Check the exact event subject format and use correct prefixes and suffixes in filters.

Not verifying the subscription after creation

You might miss misconfigurations that prevent events from arriving.

Use the show or list commands to confirm the subscription settings.

Summary

Create an Event Grid subscription with filters to receive only specific event types and subjects.

Verify the subscription details to ensure filters and destination are correct.

Delete the subscription when it is no longer needed to stop event delivery.

Practice

(1/5)

1. What is the main purpose of using filters in Azure Event Grid subscriptions?

easy

A. To receive only specific events based on criteria like event type or subject

B. To increase the number of events sent to subscribers

C. To block all events from being delivered

D. To change the event data before delivery

Event Grid subscriptions and filters in Azure - Commands & Configuration

Start learning this pattern below

Practice

Solution

Step 1: Understand Event Grid subscriptions

Step 2: Role of filters in subscriptions

Final Answer:

Quick Check:

Solution

Step 1: Identify subject prefix filter syntax

Step 2: Match the correct JSON snippet

Final Answer:

Quick Check:

Solution

Step 1: Understand filter conditions

Step 2: Check each option

Final Answer:

Quick Check:

Solution

Step 1: Check filter syntax and support

Step 2: Consider case sensitivity and subscription status

Final Answer:

Quick Check:

Solution

Step 1: Filter by event type

Step 2: Filter by subject prefix for container

Step 3: Combine filters correctly

Final Answer:

Quick Check: