Re-use variable from HostRegexp in another label #5030
Description
Do you want to request a feature or report a bug?
Feature
What did you expect to see?
Assume a Host Rule like this (docker-compose style):
labels:
- "traefik.frontend.rule=HostRegexp:{portal:.+}.example.org"
An application serves multiple portals and the application must know which portal it is serving. This information should be extracted from the requested Host.
Currently, I must spawn a service for every portal and set the header statically, like this:
- "traefik.frontend.headers.customRequestHeaders=portal:something"
It would be a very helpful feature to dynamically reuse the previously regex'd match as a variable here, in place of something.
There are multiple portals plus portal-specific api, plus microservices, all needing the portal information, so it's growing very fast.
nginx provides what I want to achieve with the following syntax:
server_name ~^(?<portal>.+?)\.example\.org$;
proxy_set_header PORTAL "$portal";
The application behind then can read the HTTP header PORTAL and behave accordingly.
As a proposal, I could imagine a go-like syntax:
- "traefik.frontend.headers.customRequestHeaders=portal:{{portal}}"
Maybe this can be achieved with middleware. If not in traefik-v1, then maybe in traefik-v2 ...