Provide transformer to set host / authority header static

[msiebeneicher]

Issue Type:

• Bug report
• Feature request

Environment:

We are running linkerd as a circuit breaker for a grpc (http2) connection.

The complete setup is docker based and we want to make a request from containerA (app) to containerB (circuit breaker) which goes to an external endpoint.

Unfortunately we can't set any headers in the used grpc client manually.

It would be nice to have a possibility to configure the host header static by the linkerd config to an explicit value. How far as I understand the transformers this should be a place for a implementation like this.

In our case the final endpoint needs the correct host header for routing. As a workaround we have to use the final url in containerA and forward the url by an /etc/hosts entry to containerB. This setup feels a bit "dirty" and is not really transparent for our use case.

[franziskagoltz]

Hey @msiebeneicher, thanks for filling this feature request.

Transformers would not work for this feature implementation, rather a custom RequestAuthorization plugin would be the way to go. This does not exist in Linkerd yet, but you can write your own and if you're so inclined, you're welcome to submit a PR so others can benefit from your change, too.

We will keep it as in open issue for future milestone planning, though we can't make any promises of when it will be released.

Thanks again!

[perrymanuk]

I would also +1 this, would make our development/stage environments a lot easier to integrate with our production.

[frvge]

I've got a similar request where I want to pass through a static Host header to the service running on Nomad. It'd be nice if we can override headers, maybe with regex support, with a possibility to reference the original incoming headers.

[franziskagoltz]

Thanks for your input @perrymanuk and @frvge!