Google Cloud LoadBalancer is unable to map tcp connection between client and LB with tcp connection

[Exilend App]

I am seeing an issue during performance testing of our application. The issue is LoadBalancer is unable to map tcp connection between client and LB with tcp connection between LB and backed instance.

When a client sends a http request first time, LB opens a new TCP connection with backed instance but when same client sends another http request then also LB creates a new TCP connection with backend instance. When we execute the same scenario directly sending requests from client to backend instance, same tcp connection is reused.

We have a limit on open TCP connections per process at backed instance so I want to know following.

1. Why LB uses an ip range when sending requests to backed servers and where it is configured ?

2. How LB maps clients TCP connections with backend TCP connections ? If there is no mapping then what is the limit of open tcp connections imposed by LB.

3. What is the response code returned by LB in case of connection reset by backed instance ?

4. What is the response code returned by LB in case of backed server’s SYN backlog queue is full.

   
   

   
   

   NGINX has some properties to configure keep-alive connections. I need to find the same for GCE LB.
   https://www.nginx.com/blog/tuning-nginx/