eventgrid_event_subscription creates incomplete function endpoint id when used with function app endpoint

[Hjortsberg]

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Terraform (and AzureRM Provider) Version

TF.ver: 0.12.24, provider.ver: 2.14

Affected Resource(s)

• azurerm_eventgrid_event_subscription_resource

Terraform Configuration Files

resource "azurerm_eventgrid_event_subscription" "main" {
  name  = var.event_subscription_name
  scope = "${data.azurerm_resources.domain.resources[local.indexdomain].id}/topics/my-domain-grid-topic"
  azure_function_endpoint {
    function_id = "${module.functionapp.id}/functions/NotificationEventHandler"
  }
}

Expected Behavior

A event subscription should be created for the function app with an AzureFunction endpoint type to the domain grid topic.

Actual Behavior

Terraform errors with following message:
eventgrid.EventSubscriptionsClient#CreateOrUpdate: Failure sending request: StatusCode=400 -- Original Error: Code="InvalidRequest" Message="Invalid ARM Id.

After some poking around, it seems that the newly added function_endpoint function_id argument does not append "/functions/NotificationEventHandler" to the end of the function resource id, causing the error message upon terraform apply.
Adding that line, as in my hcl example snippet above fixes the problem.

References

• Update Resource: azurerm_eventgrid_event_subscription #6860

[jrauschenbusch]

Hey @Hjortsberg

this is not really a bug, but maybe the error message is not meaningful enough. The function_id attribute has to point to a function, not a function app. Due to the fact that a function app can host multiple functions and one is able to create it's own function (using an eventgrid binding) it's not guaranteed that it will be named NotificationEventHandler. Hence one has to manually concatenate the function id as long as there is no data source or resource for functions. (see #7354)

[Hjortsberg]

Thanks for that clarification @jrauschenbusch.

As you say the error message together with the documentation did not make me wiser, but now I understand that this fault was on my side. I thought i tried to get the id by an exported resource field, but as you say, I used the wrong resource type. :)
I had misunderstood the innerworkings of function apps/functions.

I will close this issue now!
Have a nice day.

[ghost]

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