Azure Function App's health_check_eviction_time_in_min (in site_config) gets reset from 0 to 2 by terraform if health check isn't enabled

[vsablrin]

Is there an existing issue for this?

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Terraform Version

1.6.6

AzureRM Provider Version

3.70.0

Affected Resource(s)/Data Source(s)

azurerm_linux_function_app

Terraform Configuration Files

Any config that allows creation of a linux function app.

Debug Output/Panic Output

After this function-app resource is created, subsequent terraform plans always shows this below change, which never gets fixed by a terraform apply.

  module.funcs["datagroup"].azurerm_linux_function_app.main["instance"] will be updated in-place
  ~ resource "azurerm_linux_function_app" "main" {
        id                                = "/subscriptions/............"
        name                              = "func-app-xyz"
      ~ tags                              = {
            "category"                                       = "ABC"
        }

      ~ site_config {
          ~ health_check_eviction_time_in_min       = 0 -> 2
            # (25 unchanged attributes hidden)

            # (1 unchanged block hidden)
        }

        # (1 unchanged block hidden)
    }

Expected Behaviour

There should be no change to health_check_eviction_time_in_min planned by terraform.

Actual Behaviour

When health_check is disabled (i.e., not enabled) for a Function App (verify in portal), then the function app's health_check_eviction_time_in_min will be set to 0 by Azure. But the terraform provider wrongly tries to set it to the lowest possible non-zero value, which is 2. This leads to a lingering change in the plan, which cannot be effectively/permanently applied. When this is applied, Azure would change the eviction time back to 0 since health_check is disabled for the function-app. Terraform provider wants to change this 0 to 2 in subsequent terraform-plans. This planned output is displayed even when no change is made to the configuration (code files).

module.funcs["datagroup"].azurerm_linux_function_app.main["instance"] will be updated in-place

~ resource "azurerm_linux_function_app" "main" {
id = "/subscriptions/............"
name = "func-app-xyz"
~ tags = {
"category" = "ABC"
}

  ~ site_config {
      ~ health_check_eviction_time_in_min       = 0 -> 2
        # (25 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

    # (1 unchanged block hidden)
}

Steps to Reproduce

1. Create a function app in terraform.
2. Run a terraform plan, and it will show a planned change to the health_check_eviction_time_in_min in the site_config section.
3. Terraform apply will not make this change permanent,

Important Factoids

No response

References

https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/linux_function_app

[xiaxyi]

Thanks @vsablrin for raising this issue, as mentioned in our official guidance, the property health_check_eviction_time_in_min needs to be used together with health_check_path.
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/linux_function_app#health_check_eviction_time_in_min

[vsablrin]

Thanks @xiaxyi.
We don't specify set either health_check_eviction_time_in_min or health_check_path when creating the function app. The portal shows that health check is "disabled" for this function app. For disabled health checks, Azure sets the eviction time to 0 minutes, but terraform tries to change that to 2 minutes. The range of 2 to 10 minutes is valid only if the health check is enabled, as can be seen on the portal.