EnableAcceleratedNetworking is not always returned by the Azure virtual-machine-scale-set API

[beezly]

Using Terraform 0.10.8 and AzureRM 0.3.2, I was getting a crash when running terraform apply.

Unfortunately I can't attach the crash.log as my client is concerned about privacy, but I can send it privately if someone wants it. I've included some relevant sections in this PR which I hope will be enough to explain the problem.

I've taken a look at where the AzureRM provider is crashing in the crash.log:

2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: panic: runtime error: invalid memory address or nil pointer dereference
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1ed879f]
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4:
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: goroutine 962 [running]:
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: github.com/terraform-providers/terraform-provider-azurerm/azurerm.flattenAzureRmVirtualMachineS
caleSetNetworkProfile(0xc42186b960, 0x220101a, 0x17, 0x1fbe440)
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4:   /opt/teamcity-agent/work/222ea50a1b4f75f4/src/github.com/terraform-providers/terraform-provider-azurerm/azurerm/resource_arm_virtual_machine_scale_set.go:903 +0x27f
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: github.com/terraform-providers/terraform-provider-azurerm/azurerm.resourceArmVirtualMachineScaleSetRead(0xc42238d110, 0x21220c0, 0xc423d2a000, 0x0, 0x2bea4c0)
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4:   /opt/teamcity-agent/work/222ea50a1b4f75f4/src/github.com/terraform-providers/terraform-provider-azurerm/azurerm/resource_arm_virtual_machine_scale_set.go:733 +0xcc3
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: github.com/terraform-providers/terraform-provider-azurerm/vendor/github.com/hashicorp/terraform/helper/schema.(*Resource).Refresh(0xc423cb84e0, 0xc42216e870, 0x21220c0, 0xc423d2a000, 0xc422ebd598, 0xc420bc7b01, 0x1080001125eab)
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4:   /opt/teamcity-agent/work/222ea50a1b4f75f4/src/github.com/terraform-providers/terraform-provider-azurerm/vendor/github.com/hashicorp/terraform/helper/schema/resource.go:321 +0x199
2017-11-01T11:59:53.509Z [DEBUG] plugin.terraform-provider-azurerm_v0.3.2_x4: github.com/terraform-providers/terraform-provider-azurerm/vendor/github.com/hashicorp/terraform/helper/schema.(*Provider).Refresh(0xc42227ad20, 0xc42216e820, 0xc42216e870, 0x30d8458, 0x0, 0xc420bc7b98)

It looks like the provider fails in line 903 of resource_arm_virtual_machine_scale_set.go, where the code is trying to access a field called accelerated_networking, however... it looks like this doesn't always get returned by the Azure API (also taken from the crash.log just above where the crash happens)...

{
  "networkProfile": {
    "networkInterfaceConfigurations": [
      {
        "name": "retail-bastion-eth0",
        "properties": {
          "primary": true,
          "ipConfigurations": [
            {
              "name": "retail-dev-management-bastion-frontend-ip-configuration",
              "properties": {
                "subnet": {
                  "id": "/subscriptions/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeeee/resourceGroups/retail-dev-management-rg/providers/Microsoft.Network/virtualNetworks/retail-dev-management-vnet/subnets/retail-bastion-subnet"
                },
                "loadBalancerBackendAddressPools": [
                  {
                    "id": "/subscriptions/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeeee/resourceGroups/retail-dev-management-rg/providers/Microsoft.Network/loadBalancers/retail-dev-management-bastion-lb/backendAddressPools/retail"
                  }
                ]
              }
            }
          ]
        }
      }
    ]
  }
}

This change makes the response optional (or at least that is the intention... this is my first contribution to a Go project - I've run tests and the seem to pass, and it solves the problem I was having, but I'd very much appreciate any feedback).

[tombuildsstuff]

Hey @beezly

Thanks for this PR :)

I've just merged #480 which includes the same fix (unfortunately I didn't notice this PR until after I'd merged that, or I'd have merged this one instead!) - as such this change is now in master I'm going to close this PR for the moment - but I'd like to thank you for this contribution (and this otherwise looks good!)

Thanks!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!