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.
1
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.
There are a few different problems with the following expression:
for_each = {
[for s in toset(local.environments) : if s != "prod"]
}
-
The
forexpression is missing its result clause after the colon. If you intend to just returnsdirectly then you can just specify that variable alone between the colon and theifkeyword:<code>[for s in toset(local.environments) : s if s != "prod"]</code><code>[for s in toset(local.environments) : s if s != "prod"] </code>[for s in toset(local.environments) : s if s != "prod"] -
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 theforexpression to.Since
var.environmentsseems 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:<code>for_each = toset([for s in local.environments : s if s != "prod"])</code><code>for_each = toset([for s in local.environments : s if s != "prod"]) </code>for_each = toset([for s in local.environments : s if s != "prod"]) -
The inner
tosetyou previously had forlocal.environmentsis not really adding anything here because aforexpression 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.environmentsitself 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 thetosetin the definition of the local value instead:<code>locals {environments = toset(["dev","test","preprod","prod",])}</code><code>locals { environments = toset([ "dev", "test", "preprod", "prod", ]) } </code>locals { environments = toset([ "dev", "test", "preprod", "prod", ]) }Doing this would have no effect on the
for_eachexpression this question is about though, so this would be a meaningful change only iflocal.environmentsis used in other locations that should also treat it as a set, and that’s beyond the scope of this question.