CODEWITHSUNDEEP
azureterraformazure-aksterraform-provider-azureazure-application-gateway
cavemandaveman
cavemandaveman

Reputation: 23

Terraform state sync with external changes

I have terraform managing my infrastructure in Azure. However, there are cases where the state can get out of sync when other services are changing the infrastructure as well.

For example, I have terraform create an Application Gateway. But I also have an AKS cluster with AGIC enabled, which dynamically updates/changes rules, listeners, etc. inside of Application Gateway. So if terraform is re-run after AGIC makes some changes, terraform doesn't know and wants to reset to the default config it knows about.

Maybe this isn't possible, but is there an automated way to sync the two? It's kind of unfeasible to have to go into the terraform config and manually add the changes AGIC makes every time it does so. At this point, is it even worth managing Application Gateway with terraform?

Upvotes: 2

Views: 1115

Answers (1)

Jean-Philippe Bond
Jean-Philippe Bond

Reputation: 10679

If you really want to create the Application Gateway with Terraform, you should probably use the Lifecycle Meta-Argument ignore_changes on the attributes that will be modified by AKS. It is not perfect, but at least they can share their responsibilities without overwriting each other.

The ignore_changes feature is intended to be used when a resource is created with references to data that may change in the future, but should not affect said resource after its creation. In some rare cases, settings of a remote object are modified by processes outside of Terraform, which Terraform would then attempt to "fix" on the next run. In order to make Terraform share management responsibilities of a single object with a separate process, the ignore_changes meta-argument specifies resource attributes that Terraform should ignore when planning updates to the associated remote object.

For example :

resource "azurerm_application_gateway" "example" {
  ...

  lifecycle {
    ignore_changes = [
      http_listener,
      request_routing_rule,
      backend_http_settings
    ]
  }

  ...
}

Upvotes: 2

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