I’m looking for ideas and knowledge to understand options better to enable session affinity for my service.

Here are the details (simplified):

1. Everything is running in Kubenettes cluster (GKE).

2. Ingress class use gce

3. Service-1 (Backend for the load balancer): gateway-service is just running a Nginx server for proxy (path based routing to different service).

4. Service-2 (real service): basically core API.

Both Service-1 and Service-2 have two pods in the Kube cluster. I need session affinity due to a AI conversation function. In Nginx conf, we use POD service name to route

  location /api {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-NginX-Proxy true;
    # must append the prefix '/api' again because nginx trim the '/api' from the original path when match.
    proxy_pass http://columns:8088/api;
    proxy_ssl_session_reuse off;
    proxy_set_header Host $http_host;
    proxy_cache_bypass $http_upgrade;
    proxy_redirect off;
    # some api call takes long
    proxy_read_timeout 180;
  }

Kube conf for both service-1:

# define nebula service from the open images
apiVersion: v1
kind: Service
metadata:
  name: gateway
  labels:
    app: gateway-service
  annotations:
    cloud.google.com/backend-config: '{"default": "nginx-timeout"}'
spec:
  type: NodePort
  selector:
    app: gateway-service
  ports:
    - port: 8080
      name: http
      targetPort: 8080

Kube conf for service2:

apiVersion: v1
kind: Service
metadata:
  name: columns
spec:
  type: NodePort
  selector:
    app: columns-service
  ports:
    - port: 8088
      name: api
      targetPort: 8088
    - port: 3000
      name: web
      targetPort: 3000
    - port: 8090
      name: docs
      targetPort: 8090

I know there are a lot of articles/discussions talking about setting session affinity on kube Ingress, I did that, but I think my problem is different, if I understand correctly, the Ingress session affinity is for how Load Balancer choose my gateway service (service 1), but I need extra thing in Service 1 (Nginx) to be able to create sticky session when it proxy_pass to the service-2 which is indicated at proxy_pass http://columns:8088/api;

Seems like the key to solve this problem is here to find a solution in Nginx which can build sticky session to http://columns:8088/api, is it possible?

Exhausted my knowledge on this, I appreciate any help!