Depends_on not working

[Paul Sanders]

Hi All,

This is my first post on here, and am fairly new to Terraform, so apologies if this is down to user error. 

I have a basic main.tf file that calls upon two sub modules to deploy some Azure resources, network and storage. This is my main.tf:

# Configure the Azure Provider

provider "azurerm" {}

module "storage" {

 source = "modules/storage"

  #depends_on                = ["${azurerm_resource_group.RG01.name}"]

 storageResourceGroupName  = "${var.storageResourceGroupName}"

 location                  = "${var.location}"

 vhdStorageName            = "${var.vhdStorageName}"

 vhdStorageSku             = "${var.vhdStorageSku}"

 vhdStorageReplicationType = "${var.vhdStorageReplicationType}"

 ScriptReplicationType     = "${var.ScriptReplicationType}"

 scriptStorageName         = "${var.scriptStorageName}"

 scriptStorageSku          = "${var.scriptStorageSku}"

 diagnosticsStorageName    = "${var.diagnosticsStorageName}"

 diagnosticsStorageSku     = "${var.diagnosticsStorageSku}"

 DiagnosticReplicationType = "${var.DiagnosticReplicationType}"

}

module "network" {

 source                            = "modules/network"

 networkResourceGroupName          = "${var.networkResourceGroupName}"

 VNetName                          = "${var.VNetName}"

 NetworkCIDR                       = "${var.NetworkCIDR}"

 SubnetGatewayName                 = "${var.SubnetGatewayName}"

 SubnetGatewayCIDR                 = "${var.SubnetGatewayCIDR}"

 applicationGatewayGreenSubnetName = "${var.applicationGatewayGreenSubnetName}"

 applicationGatewaySubnetCidrGreen = "${var.applicationGatewaySubnetCidrGreen}"

 applicationGatewayBlueSubnetName  = "${var.applicationGatewayBlueSubnetName}"

 applicationGatewaySubnetCidrBlue  = "${var.applicationGatewaySubnetCidrBlue}"

 jumpboxSubnetName                 = "${var.jumpboxSubnetName}"

 jumpboxSubnetCidr                 = "${var.jumpboxSubnetCidr}"

 scaleSetBlueSubnetName            = "${var.scaleSetBlueSubnetName}"

 scaleSetSubnetCidrBlue            = "${var.scaleSetSubnetCidrBlue}"

 scaleSetGreenSubnetName           = "${var.scaleSetGreenSubnetName}"

 scaleSetSubnetCidrGreen           = "${var.scaleSetSubnetCidrGreen}"

}

And here is network.tf in modules/network:

resource "azurerm_resource_group" "NetworkResourceGroup01" {

 name     = "${var.networkResourceGroupName}"

 location = "${var.location}"

  tags {

   environment = ""

 }

}

resource "azurerm_virtual_network" "vnet" {

 name                = "${var.VNetName}"

 address_space       = "${var.NetworkCIDR}"

 location            = "${var.location}"

 resource_group_name = "${var.networkResourceGroupName}"

 depends_on          = ["azurerm_resource_group.NetworkResourceGroup01"]

  subnet {

   name           = "${var.SubnetGatewayName}"

   address_prefix = "${var.SubnetGatewayCIDR}"

 }

  subnet {

   name           = "${var.applicationGatewayGreenSubnetName}"

   address_prefix = "${var.applicationGatewaySubnetCidrGreen}"

 }

  subnet {

   name           = "${var.applicationGatewayBlueSubnetName}"

   address_prefix = "${var.applicationGatewaySubnetCidrBlue}"

 }

  subnet {

   name           = "${var.jumpboxSubnetName}"

   address_prefix = "${var.jumpboxSubnetCidr}"

 }

  subnet {

   name           = "${var.scaleSetGreenSubnetName}"

   address_prefix = "${var.scaleSetSubnetCidrGreen}"

 }

  subnet {

   name           = "${var.scaleSetBlueSubnetName}"

   address_prefix = "${var.scaleSetSubnetCidrBlue}"

 }

}

and finally, my storage.tf in modules/storage.tf

resource "azurerm_resource_group" "StorageResourceGroup01" {

 name     = "${var.storageResourceGroupName}"

 location = "${var.location}"

  tags {

   environment = ""

 }

}

resource "azurerm_storage_account" "VHDStorageAccount" {

 name                     = "${var.vhdStorageName}"

 resource_group_name      = "${var.storageResourceGroupName}"

 location                 = "${var.location}"

 account_tier             = "${var.vhdStorageSku}"

 account_replication_type = "${var.vhdStorageReplicationType}"

 depends_on               = ["azurerm_resource_group.StorageResourceGroup01"]

  #depends_on = ["${var.depends_on}"]

}

resource "azurerm_storage_account" "ScriptStorageAccount" {

 name                     = "${var.scriptStorageName}"

 resource_group_name      = "${var.storageResourceGroupName}"

 location                 = "${var.location}"

 account_tier             = "${var.scriptStorageSku}"

 account_replication_type = "${var.ScriptReplicationType}"

  depends_on = ["azurerm_resource_group.StorageResourceGroup01"]

}

resource "azurerm_storage_account" "DiagnosticStorageAccount" {

 name                     = "${var.diagnosticsStorageName}"

 resource_group_name      = "${var.storageResourceGroupName}"

 location                 = "${var.location}"

 account_tier             = "${var.diagnosticsStorageSku}"

 account_replication_type = "${var.DiagnosticReplicationType}"

 depends_on               = ["azurerm_resource_group.StorageResourceGroup01"]

  #depends_on = ["${var.depends_on}"]

}

When I run a terraform plan, I get:

* azurerm_virtual_network.vnet: Error Creating/Updating Virtual Network "PSandersTestNet01" (Resource Group "NetworkTest"): network.VirtualNetworksClient#CreateOrUpdate: Failure sending request: StatusCode=0 -- Original Error: autorest/azure: Service returned an error. Status=404 Code="ResourceGroupNotFound" Message="Resource group 'NetworkTest' could not be found."

If I re-run it again, all goes through as the resource group has been created. So it is as though depends_on is being ignored?

Thanks

Paul 

[Steven Nemetz]

It is being ignored or silently failing

Depends on doesn't work with modules. It only works on resources that are all in the same scope. So, both what is depended on and what needs it would need to be in the same module.

[Paul Sanders]

Thanks for the reply Steven. 

Do we know when cross module dependancies will come into play? Would be really helpful (even if it was waiting for the module to apply before running the next).

Regarding the storage.rf one though, the depends_on is within the same scope and module, but is still intermittent when it comes to being followed. Is there a way I can dig deeper with looking at the apply process?

Thanks

---
Kind Regards

Paul Sanders
Mob: 07988 725 883
Mail: paul.sa...@googlemail.com

On Fri, 17 Aug 2018 at 05:26, Steven Nemetz <sne...@hotmail.com> wrote:

It is being ignored or silently failing

Depends on doesn't work with modules. It only works on resources that are all in the same scope. So, both what is depended on and what needs it would need to be in the same module.

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[Jorge Ernesto Guevara Cuenca]

Did you check this https://medium.com/@bonya/terraform-adding-depends-on-to-your-custom-modules-453754a8043e? maybe can be helpful

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[Steven Nemetz]

While that example may work or at least sometimes. I believe doing that will be problematic.

Depends_on is given a list of resources that can be seen in the current scope. x.y in one module is not the same as x.y in another module. Each of these has a different absolute path in the Terraform state. Therefore they are different resources. depends_on may work if provided the resource's absolute path instead of the relative one (never tried that). But that would be very difficult to maintain.

As far as cross module dependencies. There isn't. It is all resource dependencies based on variable passing.

So, if you pass module X the value module.y.a, anything that using that value in module X now depends on module y. Since y has to finish to have outputs. Depending on how module X is written the whole module might depend on y. But remember that will be a calculated field. So, it can't be used in a count statement.