Terraform-provider-azurerm: Must provide all optional values in azurerm_eventgrid_event_subscription.subject_filter or get a TF crash

[kirk-marple]

Found a strange issue when creating Azure Event Grid subscription.

If I don't provide all the values of 'subject_filter' block, I get a hard crash (Gist below), and it says it's a Terraform bug.

From looking at the code, it shows all values as optional for subject_filter, so I'm not clear why they're all required.

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Terraform (and AzureRM Provider) Version

AzureRM: 2.12
Terraform 0.12.26

Affected Resource(s)

resource "azurerm_eventgrid_event_subscription" "event_grid_subscription" {
name = "${var.platform_name}-subscription-${var.function_name}"
scope = var.topic_id
event_delivery_schema = "EventGridSchema"
included_event_types = var.included_event_types

subject_filter {
subject_begins_with = var.subject_begins_with
subject_ends_with = var.subject_ends_with
# NOTE: commenting out this line causes this crash
case_sensitive = false
}

webhook_endpoint {
url = "${var.functions_uri}/runtime/webhooks/EventGrid?functionName=${var.function_name}&code=${var.functions_key}"
}
}

Debug Output

https://gist.github.com/kirk-marple/12c844ec9e436f4763c8eff788880bd1

Expected Behavior

Successfully create Azure Event Grid subscription to webhook.

Actual Behavior

Failed to create Azure Event Grid subscription.

Steps to Reproduce

This fails:

subject_filter {
subject_begins_with = var.subject_begins_with
subject_ends_with = var.subject_ends_with

case_sensitive = false

}

This works:

subject_filter {
subject_begins_with = var.subject_begins_with
subject_ends_with = var.subject_ends_with
case_sensitive = false
}

[jrauschenbusch]

This is a bug inside the expand function for the subject filter. Although the schema params are defined as Optional they are required as otherwise the type conversion fails due to a nil pointer dereference.

[neil-yechenwei]

Thanks for opening this issue. After tested, seems I can create this resource successfully with below tfconfig which is similar with yours. Perhaps this issue only occurred in some cases. If you want, please have a try below tfconfig to check whether the problem still exists. If still exists, could you possibly share entire tf config that trigger this problem? Thanks.

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "test" {
  name     = "acctestRG-eg-test"
  location = "westus"
}

resource "azurerm_storage_account" "test" {
  name                     = "acctestacctest"
  resource_group_name      = azurerm_resource_group.test.name
  location                 = azurerm_resource_group.test.location
  account_tier             = "Standard"
  account_replication_type = "LRS"
}

resource "azurerm_storage_queue" "test" {
  name                 = "mysamplequeue-test"
  storage_account_name = azurerm_storage_account.test.name
}

resource "azurerm_eventgrid_event_subscription" "test" {
  name  = "acctest-eg-test"
  scope = azurerm_resource_group.test.id
  event_delivery_schema = "EventGridSchema"

  storage_queue_endpoint {
    storage_account_id = azurerm_storage_account.test.id
    queue_name         = azurerm_storage_queue.test.name
  }

  included_event_types = ["Microsoft.Storage.BlobCreated", "Microsoft.Storage.BlobDeleted"]

  subject_filter {
    subject_begins_with = "test/test"
    subject_ends_with   = ".jpg"
  }
}

[kirk-marple]

Here's the whole module I'm using. I can't easily provide the entire config, since it's one part of a big infrastructure.

It may also be due to using default values ("") for subject_begins_with, subject_ends_with.

function-event-grid-subscription.zip

Hope that helps.

[neil-yechenwei]

@kirk-marple , sorry, seems I still cannot repro this issue with your tfconfig after tested. And then I also checked your debug log, seems you encountered this issue at modification stage not first creation, right? If yes, could you provide the repro steps?

[neil-yechenwei]

@kirk-marple, I think I can repro it now. Seems the failure is caused by nil pointer reference error while subject_filter from nil to map[string]interface{}. I'll submit a fix for this. And if you want to remove all values in subject_filter block, suggests to directly remove this whole block from tfconfig. Thanks.

[hashibot[bot]]

This has been released in version 2.14.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.14.0"
}
# ... other configuration ...

[hashibot[bot]]

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