gRPC reverse proxy closed tcp connection after 1000 rpc calls

[hadals]

server {
            listen 8080 http2 reuseport;
	        server_name dev-status-service-svc-protocol-50051;
            access_log off;
            http2_max_requests 10000000;
            http2_max_concurrent_streams 512;
            grpc_socket_keepalive on;

            location / {
                grpc_pass grpc://test-status;

            }
        }
        upstream test-status {
                server 172.28.254.165:50051; 
                server 172.28.254.32:50051;
                keepalive 32;
                keepalive_requests 1000000;
        }

I found that nginx can keep a connection with the client.  but, there are
still a lot of connections to the backend. so many ESTAB and TIME-WAIT .

When I use the client to connect directly to the backend service, it can
maintain a connection without disconnecting.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,283297,283732#msg-283732