Terraform-provider-azurerm: Support for pickHostnameFromBackendAddress setting on Application Gateway

[ndarilek]

I've been trying to set up an application gateway that proxies to two backend apps by FQDN. Unfortunately, with a configuration as generated by Terraform, this setup doesn't seem to work. Requests hit an application gateway with a Host: header like staging.example.com. Then they're proxied to a backend app on azurewebsites.net which expects a hostname like app-staging.azurewebsites.net, only the header still contains the original FQDN, so the app returns a 404 even though it is up. I can reach the backend by hitting the gateway IP with Curl and manually setting the host header to match the FQDN of the backend, but I don't have control over the headers after they traverse the gateway.

Dialogues with Azure support and Google searches led me to this and this which hopefully shed a little more light on the issue. I'm fairly new to Azure, so hopefully the above gives enough of an indication of what I hope can be supported, but I'm happy to answer any additional questions if I can.

Thanks!

[mdsills]

hopefully PR https://github.com/terraform-providers/terraform-provider-azurerm/pull/2658 addresses this issue

[agrcrobles]

that's great! when are you creating a new stable release? is it even possible to consume the provider from master branch?

[tombuildsstuff]

Closing since this has been fixed via #2658

@agrcrobles it's possible to build this provider locally (there's instructions for how to do that in the README) - otherwise I expect we'll be doing a release this week :)

Thanks!

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