I tend to agree with this statement, and am also wondering how the host header stays as example.com when using HTTP (because even over HTTP nginx is changing the header to app.internal.lan). As you can see in my logging statement above, I should be seeing headers in my logs ( %hr\ %hs\), however, I don’t see them.
It is really strange that I don’t have to set http-request set-header Host app.internal.lan when using HTTP in haproxy, and the redirect still works fine (even though nginx has changed the header).
Can you please advise the best way to test this using curl? I’d like to see exactly where the header is getting change. I appreciate all of the help.