请教一下，通过k8s 的ingress实现的7层负载均衡，为啥浏览器可以实现轮询，但是curl命令无法轮询，希望大佬能提供下思路

前提：

1、在k8s中配置了一个ingress，配置如下

[root@node-1 ~]# kubectl get ingress
NAME    CLASS    HOSTS               ADDRESS                     PORTS   AGE
nginx   <none>   nginx.zerchin.xyz   172.16.0.211                80      31m

[root@node-1 ~]# kubectl get ingress nginx -o yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
  name: nginx
  namespace: default
spec:
  rules:
  - host: nginx.zerchin.xyz
    http:
      paths:
      - backend:
          serviceName: nginx-test
          servicePort: http-nginx-test
        path: /

2、后端的nginx-test是一个基于nginx镜像启动的web服务

[root@node-1 ~]# kubectl get pod
NAME                         READY   STATUS    RESTARTS   AGE
nginx-test-96b89c957-77npv   1/1     Running   0          35m
nginx-test-96b89c957-bjtbs   1/1     Running   0          35m
nginx-test-96b89c957-r7g89   1/1     Running   0          35m

[root@node-1 ~]# kubectl get svc
NAME                  TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
kubernetes            ClusterIP   10.43.0.1       <none>        443/TCP        20d
nginx-test            ClusterIP   10.43.114.167   <none>        80/TCP         35m
nginx-test-nodeport   NodePort    10.43.23.216    <none>        80:32370/TCP   35m

问题现象：

1、如果我通过curl对应的service，可以实现轮询（因为后端是基于ipvs转发的）

[root@node-1 ~]# for i in `seq 1 12`;do curl 10.43.114.167;done
111
3
22
111
3
22
111
3
22
111
3
22

2、但是如果curl ingress对应的地址，反而不能实现轮询

[root@node-1 ~]# for i in `seq 1 12`;do curl nginx.zerchin.xyz ;done
3
22
111
22
111
111
3
3
3
3
22
22

3、如果是通过浏览器访问，通过Ctrl+R刷新浏览器，这个却是可以实现轮询

这个结果跟之前通过curl对应的service是一样的

因为k8s的ingress-nginx是基于lua实现的，我不太懂lua语言，所以要请教一下大佬们，为啥curl和浏览器访问的结果不一样。  

排查：

通过Postman工具，如果勾选了connection：keep-alive，就可以实现轮询，取消了这个header，就无法轮询，想知道nginx的什么语法可以控制基于connection：keep-alive控制负载的轮询

k8s ingress-controller相关的nginx.conf配置

        server {
                server_name nginx.zerchin.xyz ;
                
                listen 80  ;
                listen 443  ssl http2 ;
                
                set $proxy_upstream_name "-";
                
                ssl_certificate_by_lua_block {
                        certificate.call()
                }
                
                location / {
                        
                        set $namespace      "default";
                        set $ingress_name   "nginx";
                        set $service_name   "nginx-test";
                        set $service_port   "http-nginx-test";
                        set $location_path  "/";
                        
                        rewrite_by_lua_block {
                                lua_ingress.rewrite({
                                        force_ssl_redirect = false,
                                        ssl_redirect = true,
                                        force_no_ssl_redirect = false,
                                        use_port_in_redirects = false,
                                })
                                balancer.rewrite()
                                plugins.run()
                        }
                        
                        # be careful with `access_by_lua_block` and `satisfy any` directives as satisfy any
                        # will always succeed when there's `access_by_lua_block` that does not have any lua code doing `ngx.exit(ngx.DECLINED)`
                        # other authentication method such as basic auth or external auth useless - all requests will be allowed.
                        #access_by_lua_block {
                        #}
                        
                        header_filter_by_lua_block {
                                lua_ingress.header()
                                plugins.run()
                        }
                        
                        body_filter_by_lua_block {
                        }
                        
                        log_by_lua_block {
                                balancer.log()
                                
                                monitor.call()
                                
                                plugins.run()
                        }
                        
                        port_in_redirect off;
                        
                        set $balancer_ewma_score -1;
                        set $proxy_upstream_name "default-nginx-test-http-nginx-test";
                        set $proxy_host          $proxy_upstream_name;
                        set $pass_access_scheme  $scheme;
                        
                        set $pass_server_port    $server_port;
                        
                        set $best_http_host      $http_host;
                        set $pass_port           $pass_server_port;
                        
                        set $proxy_alternative_upstream_name "";
                        
                        client_max_body_size                    1m;
                        
                        proxy_set_header Host                   $best_http_host;
                        
                        # Pass the extracted client certificate to the backend
                        
                        # Allow websocket connections
                        proxy_set_header                        Upgrade           $http_upgrade;
                        
                        proxy_set_header                        Connection        $connection_upgrade;
                        
                        proxy_set_header X-Request-ID           $req_id;
                        proxy_set_header X-Real-IP              $remote_addr;
                        
                        proxy_set_header X-Forwarded-For        $remote_addr;
                        
                        proxy_set_header X-Forwarded-Proto      $pass_access_scheme;
                        
                        proxy_set_header X-Forwarded-Host       $best_http_host;
                        proxy_set_header X-Forwarded-Port       $pass_port;
                        
                        proxy_set_header X-Scheme               $pass_access_scheme;
                        
                        # Pass the original X-Forwarded-For
                        proxy_set_header X-Original-Forwarded-For $http_x_forwarded_for;
                        
                        # mitigate HTTPoxy Vulnerability
                        # https://www.nginx.com/blog/mitigating-the-httpoxy-vulnerability-with-nginx/
                        proxy_set_header Proxy                  "";
                        
                        # Custom headers to proxied server
                        
                        proxy_connect_timeout                   5s;
                        proxy_send_timeout                      60s;
                        proxy_read_timeout                      60s;
                        
                        proxy_buffering                         off;
                        proxy_buffer_size                       4k;
                        proxy_buffers                           4 4k;
                        
                        proxy_max_temp_file_size                1024m;
                        
                        proxy_request_buffering                 on;
                        proxy_http_version                      1.1;
                        
                        proxy_cookie_domain                     off;
                        proxy_cookie_path                       off;
                        
                        # In case of errors try the next upstream server before returning an error
                        proxy_next_upstream                     error timeout;
                        proxy_next_upstream_timeout             1;
                        proxy_next_upstream_tries               3;
                        
                        proxy_pass http://upstream_balancer;
                        
                        proxy_redirect                          off;
                        
                }
                
        }

ingress相关参数文档：https://github.com/kubernetes/ingress-nginx/blob/master/docs/user-guide/nginx-configuration/annotations.md