Envoy config for routing consistently to a StatefulSet

envoy_config.yaml

  files:
    envoy.yaml: |-
      ## refs:
      ## - https://www.envoyproxy.io/docs/envoy/latest/start/start#quick-start-to-run-simple-example
      ## - https://raw.githubusercontent.com/envoyproxy/envoy/master/configs/google_com_proxy.v2.yaml
      admin:
        access_log_path: /dev/stdout
        address:
          socket_address:
            address: 0.0.0.0
            port_value: 9901
      static_resources:
        listeners:
        - name: listener_0
          address:
            socket_address:
              address: 0.0.0.0
              port_value: 80
          filter_chains:
          - filters:
            - name: envoy.http_connection_manager
              config:
                access_log:
                - name: envoy.file_access_log
                  config:
                    path: /dev/stdout
                stat_prefix: go-riot-envoy-http
                route_config:
                  name: local_route
                  virtual_hosts:
                  - name: local_service
                    domains: ["*"]
                    routes:
                    - match:
                        prefix: "/"
                      route:
                        cluster: go_riot
                http_filters:
                - name: envoy.lua
                  config:
                    inlineCode: |
                      function envoy_on_request(request_handle)
                        local uid = request_handle:headers():get("x-user-id")
                        local ordinal = tostring(tonumber(uid) % 3)
                        request_handle:headers():replace(":authority", "backend-go-riot-" .. ordinal)
                      end
                      function envoy_on_response(response_handle)
                        body_size = response_handle:body():length()
                        response_handle:headers():add("response-body-size", tostring(body_size))
                      end
                - name: envoy.router
        clusters:
        - name: go_riot
          connect_timeout: 2s
          type: strict_dns
          dns_lookup_family: AUTO
          lb_policy: ROUND_ROBIN
          hosts:
            - socket_address:
                address: backend-go-riot-0
                port_value: 8887
            - socket_address:
                address: backend-go-riot-1
                port_value: 8887
            - socket_address:
                address: backend-go-riot-2
                port_value: 8887

I have a StatefuleSet running with hostnames:
backend-go-riot-0
backend-go-riot-1
backend-go-riot-2

I am able to successfully hit the pods in the stateful set with:
kubectl port-forward pod/backend-go-riot-0 8887
curl localhost:8887 -> returns a 404 as expected

However, the proxy does not seem to be able to understand that the pods are available and can be routed to.