default-service

Respond to all incoming HTTP requests with a message.

Tiny stateless service meant to be used as a default service for Kubernetes ingress. Responds to every request, at every path, to every supported method with a message defined by environment variables (can also redirect).

Configuration

There are five environment variables used for configuration:

Variable	Values	Default	Required
PORT	1-65535	80	No
STATUS_CODE	HTTP Status code	404	No
LOG	true/false	true	No
ACTION_TYPE	XML/JSON/Text/Redirect	Text	No
ACTION_DATA	Content to send		Yes

For example, to send an XML response you would configure the environment variables as the following:

Variable	Value
ACTION_TYPE	XML
ACTION_DATA	"<Error><Message>Hello there!</Message></Error>"

For action type Redirect, ACTION_DATA represents the URI to redirect to.

ACTION_DATA string replacements

Before sending off the response, the following strings get replaced:

• $HOST gets replaced with the request's host header
• $PATH gets replaced with the request's path

Docker

The docker image is weilbyte/default-service, use latest tag. Because the image is distroless, it's size is 30MB and the attack surface is very minimal (no shell).

Configuring ingress

First, you need to deploy the container and create a service that points to it (port 80).

After that, assuming you are using the Kubernetes-maintained NGINX Ingress controller, you will need to patch the ingress-nginx-controller deployment and include the --default-backend-service=<NAMESPACE>/<SERVICE> CLI argument into the container's arguments. Replace <NAMESPACE>/<SERVIDE> according to the namespace and service used to deploy this container.

Example Kustomize file with patch:

namespace: ingress-nginx # SSL added and removed here ;>)
resources:
  - github.com/kubernetes/ingress-nginx//deploy/static/provider/baremetal
patches:
  - target:
      kind: Deployment
      name: ingress-nginx-controller
    patch: |-
      - op: add
        path: /spec/template/spec/containers/0/args/-
        value: --default-backend-service=default-service-namespace/default-service-service

After that, your default-service deployment will catch any request not matching any ingress hostnames.