Azure Function not being triggered from Event Grid Topic Subscription

Richard Campbell 16

Hello. I have setup an Event Grid Topic with two Event Subscriptions. The first Event Subscription is a webhook to test an Azure Function locally in visual studio, I can invoke this by using the Azure CLI to sent a command to trigger the Event Grid Topic
https://learn.microsoft.com/en-us/azure/event-grid/custom-event-to-function#send-an-event-to-your-topic

The other Event Subscription is for an Azure Function to be triggered. It is an identical function to the one in Visual Studio, I have published it to Azure and can verify it is up and running.

However when I raise an Event to the Topic only the Webhook is triggered, not the Azure Function hosted. I have configured all App Settings Key Values correctly however I cannot ever seem to trigger the function when it is published to Azure. I can monitor diagnostics for the Event Grid Topic and can see Delivery Failure Events on the timeline, when I inspect the logs the "outcome" property of the logs implies that the resource is NotFound, however Azure shows the function is up, running and bound to the topic.

Any support would be appreciative, happy to provide more information on the context.

MayankBargali-MSFT 69,846 Reputation points

2022-04-07T04:16:04.147+00:00

@Richard Campbell Thanks for reaching out and apology for the inconvenience due to this issue. As per your analysis if you see the logs as "resource is NotFound" so looks like the webhook endpoint might be incorrect/changed after the validation event as you have already validated that the function app is in a running state.

Can you please reconfigure the webhook endpoint as function again and verify if it helps you to resolve the issue. If it didn't help then please refer to my private comment so you can share more details only to my private comment.
Carlos Jourdan 5 Reputation points

2023-06-02T01:50:15.6733333+00:00

Hi. I'm running into exactly the same problem. NotFound messages when trying to trigger azure functions, but works fine for other subscriptions (e.g. storage queue). Did you have any luck fixing this?
Sreenivas Angara 0 Reputation points

2023-08-03T23:19:18.3966667+00:00

I have the same problem. This part does not work.

https://learn.microsoft.com/en-us/azure/event-grid/custom-event-to-function

However, I got previous (this) section to work.

https://learn.microsoft.com/en-us/azure/event-grid/custom-event-quickstart-portal
Ben Gimblett 3,735 Reputation points Microsoft Employee

2023-09-04T15:03:18.4266667+00:00

By setting up a Az function (Event grid trigger) using Az portal designer, using Az portal to create a custom topic with subscription (i chose to subscribe to custom event type "demo") pointed at the function i just created and using CLI to issue an event with a unique ID and date time (and event type "demo") was enough to test the function was invoked correctly and the custom event received

please let us know the error you encountered

keep in mind two ways to do this are possible
(1) as above using the function binding to event grid - this encapsulates the handshake required to verify the subscription endpoint (no extra effort is needed)
(2) by creating an http function with an http trigger (could be any http endpoint) and pointing the event grid subscription to this . The event grid viewer sample (in the last tutorial linked above) is an example of this https://github.com/Azure-Samples/azure-event-grid-viewer.git and here the subscription validation code needs to be included (as it is in the sample)

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Azure Function not being triggered from Event Grid Topic Subscription