Controlling Host Header Transformation for Regional Backend Routing in Envoy Gateway

[Tyrone-W]

Hi,

I have deployed Envoy Gateway using Helm (version 1.3.0) and am in the process of configuring it to manage traffic routing between multiple Kubernetes clusters in different regions. I am seeking assistance with a specific requirement I have encountered during this setup.

Use Case

We define a primary HTTPRoute using a common FQDN, such as example.com. This route should direct traffic to regional backends with FQDNs like example.region1.com and example.region2.com. However, the backend clusters need to receive the regional FQDN in the host header to match against their ingress configurations.

Expected Behavior

When a request is routed from example.com, the Envoy Gateway should have an option available to overwrite the host header with the hostname value defined in the backend/service(externalname) resource for the backend it's routing to.

Actual Behavior

The original host header (example.com) is being forwarded to the backend clusters, which do not have ingress configurations in place, resulting in routing issues.

Request for Assistance

In the generated Envoy configuration, within the dynamic_listeners section under default_filter_chain, I noticed that the server_header_transformation key is set to PASS_THROUGH. Is there a way to modify or control this setting?
Is there a configuration option or workaround in Envoy Gateway that allows the host header to be dynamically replaced with the hostname of the targeted backend before forwarding?
Is there another approach for this scenario that can be recommended?

Thanks

[arkodg]

hey this is possible today, check out https://gateway.envoyproxy.io/docs/tasks/traffic/http-urlrewrite/#rewrite-url-host-name-by-header-or-backend

[Tyrone-W]

Thankyou for this, is there a way to proxy the traffic to the backend instead of redirecting? If I can healthcheck and loadbalance to these backends this will work.

[arkodg]

above example does send traffic to the backend

[Tyrone-W]

Sorry, the backend itself was redirecting from http to https and I thought it was envoy redirecting to the backend.

Appreciate the quick response