How do I pass a Host header to my loadbalancer backend

Traefik Traefik v2
#1

I am testing locally with curl and without a Host header "curl http://0.0.0.0/remote_api"

My remote api is receiving requests with the Host "0.0.0.0" and therefore it is unable to route my request. Is there a way to tell the loadbalancer to use a specified Host header?

I've tried a few things including a middleware to add a custom Host header but it did not work.

I have the following setup:

[http.services]
  [http.services.remote_api.loadBalancer]
    [[http.services.remote_api.loadBalancer.servers]]
      url = "https://remote_api.example.com/"
#2

Hello @mbarany,

First, When you are using curl locally, curl will use your target host (in this case 0.0.0.0) and it will use it as the host header.

If you want to use a specific host header, add a DNS entry for it into your local DNS resolver or host file, like 127.0.0.1 example.com, and then use example.com/remote_api as your request.

Note that if you use a custom host like example.com, you will need to ensure that your traefik router matches the host you are sending.

Secondly: When you set a backend URL that is a DNS name, the backend request will be made with that host header. Otherwise the backend request would not work properly.

If you want to proxy to a remote site, while preserving the original request host header, the backend URL has to be IP-based.

#3

Thanks although I think I figured out my issue.

The solution is to add passHostHeader = false on [http.services. remote_api.loadBalancer]

For some reason I had tried to add it to [[http.services.remote_api.loadBalancer.servers]] instead, but after re-reading the docs I found my issue.