Merge pull request #219848 from fangchen0601/eventgrid_bestpractice

add event grid subscription tips

Author: prmerger-automator[bot]

articles/communication-services/quickstarts/call-automation/callflows-for-customer-interactions.md

@@ -35,12 +35,14 @@ In this quickstart, you'll learn how to build an application that uses the Azure
 
 IncomingCall is an Azure Event Grid event for notifying incoming calls to your Communication Services resource. To learn more about it, see [this guide](../../concepts/call-automation/incoming-call-notification.md). 
 1. Navigate to your resource on Azure portal and select `Events` from the left side menu.
-1. Select `+ Event Subscription` to create a new subscription. 
-1. Filter for Incoming Call event. 
-1. Choose endpoint type as web hook and provide the public url generated for your application by ngrok. Make sure to provide the exact api route that you programmed to receive the event previously. In this case, it would be <ngrok_url>/api/incomingCall. 
-![Screenshot of portal page to create a new event subscription.](./media/event-susbcription.png)
+2. Select `+ Event Subscription` to create a new subscription.
+3. Filter for Incoming Call event.
+4. Choose endpoint type as web hook and provide the public url generated for your application by ngrok. Make sure to provide the exact api route that you programmed to receive the event previously. In this case, it would be <ngrok_url>/api/incomingCall.
 
-1. Select create to start the creation of subscription and validation of your endpoint as mentioned previously. The subscription is ready when the provisioning status is marked as succeeded. 
+    ![Screenshot of portal page to create a new event subscription.](./media/event-susbcription.png)
+
+    If your application does not send 200Ok back to Event Grid in time, Event Grid will use exponential backoff retry to send the incoming call event again. However, an incoming call only rings for 30 seconds, and acting on a call after that will not work. To avoid retries after a call expires, we recommend setting the retry policy in the `Additional Features` tab as: Max Event Delivery Attempts to 2 and Event Time to Live to 1 minute. Learn more about retries [here](../../../event-grid/delivery-and-retry.md).
+5. Select create to start the creation of subscription and validation of your endpoint as mentioned previously. The subscription is ready when the provisioning status is marked as succeeded.
 
 This subscription currently has no filters and hence all incoming calls will be sent to your application. To filter for specific phone number or a communication user, use the Filters tab.
 

articles/communication-services/quickstarts/call-automation/redirect-inbound-telephony-calls.md

@@ -31,10 +31,14 @@ Get started with Azure Communication Services by using the Call Automation SDKs
 
 IncomingCall is an Azure Event Grid event for notifying incoming calls to your Communication Services resource. To learn more about it, see [this guide](../../concepts/call-automation/incoming-call-notification.md). 
 1. Navigate to your resource on Azure portal and select `Events` from the left side menu.
-1. Select `+ Event Subscription` to create a new subscription. 
-1. Filter for Incoming Call event. 
-1. Choose endpoint type as web hook and provide the public url generated for your application by ngrok. Make sure to provide the exact api route that you programmed to receive the event previously. In this case, it would be <ngrok_url>/api/incomingCall. 
-1. Select create to start the creation of subscription and validation of your endpoint as mentioned previously. The subscription is ready when the provisioning status is marked as succeeded. 
+2. Select `+ Event Subscription` to create a new subscription.
+3. Filter for Incoming Call event.
+4. Choose endpoint type as web hook and provide the public url generated for your application by ngrok. Make sure to provide the exact api route that you programmed to receive the event previously. In this case, it would be <ngrok_url>/api/incomingCall.
+
+    ![Screenshot of portal page to create a new event subscription.](./media/event-susbcription.png)
+
+    If your application does not send 200Ok back to Event Grid in time, Event Grid will use exponential backoff retry to send the incoming call event again. However, an incoming call only rings for 30 seconds, and acting on a call after that will not work. To avoid retries after a call expires, we recommend setting the retry policy in the `Additional Features` tab as: Max Event Delivery Attempts to 2 and Event Time to Live to 1 minute. Learn more about retries [here](../../../event-grid/delivery-and-retry.md).
+5. Select create to start the creation of subscription and validation of your endpoint as mentioned previously. The subscription is ready when the provisioning status is marked as succeeded.
 
 This subscription currently has no filters and hence all incoming calls will be sent to your application. To filter for specific phone number or a communication user, use the Filters tab.