CORS headers not added on 504 gateway timeout

[rocketraman]

Is this a request for help? No

What keywords did you search in NGINX Ingress controller issues before filing this one? cors 504 gateway timeout

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Is this a BUG REPORT or FEATURE REQUEST? (choose one): BUG REPORT

NGINX Ingress controller version: 0.11.0

Kubernetes version (use kubectl version):

Server Version: version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.5", GitCommit:"17d7182a7ccbb167074be7a87f0a68bd00d58d97", GitTreeState:"clean", BuildDate:"2017-08-31T08:56:23Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

Environment:

• Cloud provider or hardware configuration: Azure acs-engine
• OS (e.g. from /etc/os-release):

NAME="Ubuntu"
VERSION="16.04.2 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04.2 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
VERSION_CODENAME=xenial
UBUNTU_CODENAME=xenial

• Kernel (e.g. uname -a): Linux k8s-master-18117938-0 4.4.0-104-generic #127-Ubuntu SMP Mon Dec 11 12:16:42 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
• Install tools: acs-engine
• Others:

What happened:

I have an ingress service with CORs enabled. When the ingress upstream does not respond for some reason, the nginx controller returns a 504 gateway timeout as expected. However, the 504 timeout does not contain the required CORs headers to allow the browser code to read the error response.

What you expected to happen:

The 504 error should contain the requested CORS headers.

How to reproduce it (as minimally and precisely as possible):

Create a service that does nothing with the request, to cause a gateway timeout. Configure the ingress with any CORs rules, and enable CORs. Try to make the request.

Anything else we need to know: No