go-router | base system design for Soft-routing base

I am using Spring Cloud Netflix Ribbon in combination with Eureka in a Cloud Foundry environment.

The use case I am trying to implement is the following:

• I have a running CF application named address-service with several instances spawned.

• The instances are registering to Eureka by the service name address-service

• I have added custom metadata to service instances using
  eureka.instance.metadata-map.applicationId: ${vcap.application.application_id}

• I want to use the information in Eureka's InstanceInfo (in particular the metadata and how many service instances are available) for setting a CF HTTP header "X-CF-APP-INSTANCE" as described here.

• The idea is to send a Header like "X-CF-APP-INSTANCE":"appIdFromMetadata:instanceIndexCalculatedFromNoOfServiceInstances" and thus "overrule" CF's Go-Router when it comes to load balancing as described at the bottom of this issue.

I believe to set headers, I need to create a custom RibbonClient implementation - i.e. in plain Netflix terms a subclass of AbstractLoadBalancerAwareClient as described here - and override the execute() methods.

However, this does not work, as Spring Cloud Netflix Ribbon won't read the class name of my CustomRibbonClient from application.yml. It also seems Spring Cloud Netflix wraps quite a bit of classes around the plain Netflix stuff.

I tried implementing a subclass of RetryableRibbonLoadBalancingHttpClient and RibbonLoadBalancingHttpClient which are Spring classes. I tried giving their class names in application.yml using ribbon.ClientClassName but that does not work. I tried to override beans defined in Spring Cloud's HttpClientRibbonConfiguration but I cannot get it to work.

So I have two questions:

1. is my assumption correct that I need to create a custom Ribbon Client and that the beans defined here and here won't do the trick?

2. How to do it properly?

Any ideas are greatly appreciated, so thanks in advance!

Update-1

I have dug into this some more and found RibbonAutoConfiguration.

This creates a SpringClientFactory which provides a getClient() method that is only used in RibbonClientHttpRequestFactory (also declared in RibbonAutoConfiguration).

Unfortunately, RibbonClientHttpRequestFactory hard-codes the client to Netflix RestClient. And it does not seem possible to override either SpringClientFactory nor RibbonClientHttpRequestFactory beans.

I wonder if this is possible at all.