Azure Question posted in
The official documentation to get you started can be found here.

Azure – Using Terraform For_Each and For commands to filter elements

I have a Terraform locals.tf file like the below snippet, which contains my environment definition.

locals {
    environments = [
    "dev", 
    "test", 
    "preprod",
    "prod"
   ]
}

I am now looking to create an identical resource, an Azure monitor metric alert in this case, for each of the listed environments (except prod). I am attempting to do so using a For_Each loop in the resource block of my main.tf file, a snippet of which is shown below:

resource "azurerm_monitor_metric_alert" "main" {
  for_each = {
     [for s in toset(local.environments) : if s != "prod"] 
  }   
  name = "${each.key}-metric-alert"
  resource_group_name = azurerm_resource_group.rg.name
  scopes              = [azurerm_storage_account.to_monitor[each.key].id]
  [..........ADDITIONAL NON-PROD RESOURCE CONFIG...........]

For the prod environment though, the monitor alert requires a slightly different set of configuration from the others, and so what I’d like to do is filter out that environment from the locals.tf file and then using another azurerm_monitor_metric_alert resource block, configure it along the lines of the below snippet:

   resource "azurerm_monitor_metric_alert" "main" {
      for_each = {
         [for s in toset(local.environments) : if s == "prod"] 
      } 
      name = "${each.key}-metric-alert"
      resource_group_name = azurerm_resource_group.rg.name
      scopes              = [azurerm_storage_account.to_monitor[each.key].id] 
      [..........ADDITIONAL PROD CONFIG...........]

I have the tried the above and various other implementations, but unfortunately I simply can’t get this to work. Would greatly appreciate some assistance here.

Tags:

2

Answers


  1. 0

    You didn’t specify what error you get but your for loops are missing one argument:

    [for s in toset(local.environments) : s if s != "prod"]

    And:

    [for s in toset(local.environments) : s if s == "prod"]

    Also I`m not sure if you need this toset there. It might be required to put the whole for loop inside toset and not local.environments.

    Login or Signup to reply.
  2. 0

    There are a few different problems with the following expression:

      for_each = {
     [for s in toset(local.environments) : if s != "prod"] 
  }

    1. The for expression is missing its result clause after the colon. If you intend to just return s directly then you can just specify that variable alone between the colon and the if keyword:

      [for s in toset(local.environments) : s if s != "prod"]

    2. The braces { } around this for expression are not valid. That syntax is for constructing an object-typed value, but for that to work you’d need to specify an attribute to assign the result of the for expression to.

      Since var.environments seems to be just a bunch of strings, I expect you probably want to construct a set of strings directly, without any wrapping map/object, like this:

      for_each = toset([for s in local.environments : s if s != "prod"])

    3. The inner toset you previously had for local.environments is not really adding anything here because a for expression effectively treats a set of strings like a list of those strings in lexical order. You can safely remove it like I did in my most recent example above, and that would be sufficient for this particular use of `local.environments.

      If you want to communicate that local.environments itself is semantically a set — which might be helpful for future maintainers of your module trying to understand what you intended — then you might choose to place the toset in the definition of the local value instead:

      locals {
  environments = toset([
    "dev", 
    "test", 
    "preprod",
    "prod",
  ])
}

      Doing this would have no effect on the for_each expression this question is about though, so this would be a meaningful change only if local.environments is used in other locations that should also treat it as a set, and that’s beyond the scope of this question.

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search