What this covers

The Microsoft Learn exercise deploys an Event Grid namespace with a namespace topic, adds event subscriptions filtered by event type, and runs a Python Flask app that publishes content moderation events and reads them back with pull delivery. You see how filtering splits flagged, approved and all events into separate subscriptions, and how acknowledge, release and reject settle each event. Allow about 30 minutes.

Exam weight: Connect to and consume Azure services (20–25%)

Skills measured

"Implement event-driven workflows by using Azure Event Grid, including filters, custom events, and retries"

Key concepts

What you build

Resource	Purpose
Event Grid namespace	Container for namespace topics; endpoint `https://<namespace>.<region>-1.eventgrid.azure.net`
Namespace topic `moderation`	Receives CloudEvents from the app
Subscription `flagged`	Queue (pull) delivery, filter type `com.contoso.ai.ContentFlagged`
Subscription `approved`	Filter type `com.contoso.ai.ContentApproved`
Subscription `all-events`	No filter
Role assignments	EventGrid Data Sender and EventGrid Data Receiver for your user

Prerequisites: an Azure subscription, Visual Studio Code, Python 3.12 or later, and a current Azure CLI.

Pull delivery settlement

receive() returns events with a lock token. Within the lock duration you must settle each one:

Operation	Effect	Like Service Bus...
`acknowledge`	Done, removed	`complete`
`release`	Back to the subscription for redelivery (optionally after a delay)	`abandon`
`reject`	Not processable; dead-lettered if a dead-letter destination is set, else dropped	`dead_letter`

If the lock expires, the event is redelivered. After the subscription's max delivery count it's dead-lettered or dropped. Pull subscriptions also have an event retention period.

How it works

Unlike push, nothing calls your app. The app connects outbound, so it works behind a firewall with no public endpoint and no validation handshake.

Hands-on

Azure portal

Search Event Grid Namespaces > + Create, pick resource group, name and region.
In the namespace, under Event broker, select Topics > + Topic, name it moderation.
Open the topic > Subscriptions > + Subscription. Keep Cloud Events v1.0 and Delivery mode: Queue.
On Filters, add event type com.contoso.ai.ContentFlagged. On Additional features, review retention, max delivery count, lock duration and dead-lettering.
Repeat for approved and all-events.

Azure CLI

Azure CLI / Bash

RG=<resource-group>; NS=<namespace>; LOC=eastus
az group create -n $RG -l $LOC
az eventgrid namespace create -g $RG -n $NS -l $LOC
az eventgrid namespace topic create -g $RG --namespace-name $NS -n moderation

az eventgrid namespace topic event-subscription create -g $RG --namespace-name $NS \
  --topic-name moderation -n flagged \
  --delivery-configuration "{deliveryMode:Queue,queue:{receiveLockDurationInSeconds:60,maxDeliveryCount:5,eventTimeToLive:P1D}}" \
  --filters-configuration "{includedEventTypes:['com.contoso.ai.ContentFlagged']}"

az eventgrid namespace topic event-subscription create -g $RG --namespace-name $NS \
  --topic-name moderation -n all-events \
  --delivery-configuration "{deliveryMode:Queue,queue:{receiveLockDurationInSeconds:60}}"

SCOPE=$(az eventgrid namespace show -g $RG -n $NS --query id -o tsv)
ME=$(az ad signed-in-user show --query id -o tsv)
az role assignment create --assignee $ME --role "EventGrid Data Sender" --scope $SCOPE
az role assignment create --assignee $ME --role "EventGrid Data Receiver" --scope $SCOPE

az eventgrid namespace show -g $RG -n $NS --query "topicsConfiguration.hostname" -o tsv
# Clean up when done
az group delete -n $RG --yes --no-wait

Older CLI versions may need az extension add --name eventgrid for the namespace commands. Create the approved subscription the same way as flagged, with its own event type.

Python

# pip install azure-eventgrid azure-identity
from azure.identity import DefaultAzureCredential
from azure.core.messaging import CloudEvent
from azure.eventgrid import EventGridSenderClient, EventGridReceiverClient

ENDPOINT = "https://<namespace>.<region>-1.eventgrid.azure.net"
cred = DefaultAzureCredential()

def main():
    sender = EventGridSenderClient(ENDPOINT, cred, namespace_topic="moderation")
    sender.send([
        CloudEvent(type="com.contoso.ai.ContentFlagged", source="/moderation",
                   subject="/items/img-7", data={"itemId": "img-7", "confidence": 0.91}),
        CloudEvent(type="com.contoso.ai.ContentApproved", source="/moderation",
                   subject="/items/img-8", data={"itemId": "img-8", "confidence": 0.99}),
    ])

    receiver = EventGridReceiverClient(ENDPOINT, cred, namespace_topic="moderation",
                                       subscription="flagged")
    details = receiver.receive(max_events=10, max_wait_time=10)
    ack, bad = [], []
    for d in details:
        print(d.event.type, d.event.data)
        (ack if d.event.data.get("itemId") else bad).append(d.broker_properties.lock_token)
    if ack:
        receiver.acknowledge(lock_tokens=ack)
    if bad:
        receiver.reject(lock_tokens=bad)

if __name__ == "__main__":
    main()

Expected result: flagged returns only img-7, approved only img-8, and all-events both. Role assignments can take a few minutes to apply.

Exam traps

Observation	Cause
`flagged` returns every event	No event-type filter on the subscription
Events come back after a few minutes	Not acknowledged before the lock expired
401/403 when receiving	Missing EventGrid Data Receiver role
Can't publish Event Grid-schema events	Namespace topics accept CloudEvents only

Quick review

Event Grid namespaces host namespace topics with queue (pull) or push subscriptions.
Filters on namespace subscriptions are set with --filters-configuration.
Received events carry a lock token used to acknowledge, release or reject.
Senders need EventGrid Data Sender; pull receivers need EventGrid Data Receiver.
Pull delivery needs no public endpoint and no validation handshake.
Clean up with az group delete.

Practice

Practice: Event Grid questions

Exercise - Publish and receive events with Azure Event Grid