Custom-error-pages image does not work with media content

[mdanylyuk]

What happened: I built a custom-error-pages docker image that contains my pages with media content, e.g. png/jpg images. Then I tried to deploy it as the default backend.

But when I try to open this error page I don't see my images on the page, eg. icon/backgroud. And as I understand it's because Nginx set Content-Type header text/html for everything.

2024/02/27 11:32:08 serving custom error response for code 404 and format text/html from file /www/404.html
2024/02/27 11:32:28 format not specified. Using text/html
2024/02/27 11:32:28 serving custom error response for code 503 and format text/html from file /www/503.html
2024/02/27 11:32:29 format not specified. Using text/html

What you expected to happen: Ingress controller has to open my error page with all media content.

Ingress Controller returns, or does not return, X-Format header to the default-backend here

NGINX Ingress controller version (exec into the pod and run nginx-ingress-controller --version.):

v1.9.4

Kubernetes version (use kubectl version):

Server Version: v1.27.7

Environment:

• Cloud provider or hardware configuration: Azure

• OS (e.g. from /etc/os-release): AKSUbuntu-2204gen2containerd-202311.07.0

• Kernel (e.g. uname -a):

• Install tools:

  • Please mention how/where was the cluster created like kubeadm/kops/minikube/kind etc.

• Basic cluster related info:

  • kubectl version
  • kubectl get nodes -o wide

• How was the ingress-nginx-controller installed:

  • If helm was used then please show output of helm ls -A | grep -i ingress
  • If helm was used then please show output of helm -n <ingresscontrollernamespace> get values <helmreleasename>
  • If helm was not used, then copy/paste the complete precise command used to install the controller, along with the flags and options used
  • if you have more than one instance of the ingress-nginx-controller installed in the same cluster, please provide details for all the instances

• Current State of the controller:

  • kubectl describe ingressclasses
  • kubectl -n <ingresscontrollernamespace> get all -A -o wide
  • kubectl -n <ingresscontrollernamespace> describe po <ingresscontrollerpodname>
  • kubectl -n <ingresscontrollernamespace> describe svc <ingresscontrollerservicename>

• Current state of ingress object, if applicable:

  • kubectl -n <appnamespace> get all,ing -o wide
  • kubectl -n <appnamespace> describe ing <ingressname>
  • If applicable, then, your complete and exact curl/grpcurl command (redacted if required) and the reponse to the curl/grpcurl command with the -v flag

• Others:

  • Any other related information like ;
  • copy/paste of the snippet (if applicable)
  • kubectl describe ... of any custom configmap(s) created and in use
  • Any other related information that may help

How to reproduce this issue:

Anything else we need to know:

[longwuyuan]

/triage accepted /help

[k8s-ci-robot]

@longwuyuan: This request has been marked as needing help from a contributor.

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In response to [this](https://github.com/kubernetes/ingress-nginx/issues/11029): >/triage accepted >/help Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[github-actions[bot]]

This is stale, but we won't close it automatically, just bare in mind the maintainers may be busy with other tasks and will reach your issue ASAP. If you have any question or request to prioritize this, please reach #ingress-nginx-dev on Kubernetes Slack.