Consider this NodePort service:

k describe service myservice
...
Type:                     NodePort
IP:                       10.15.248.153
Port:                     myservice  8080/TCP
TargetPort:               8080/TCP
NodePort:                 myservice  30593/TCP
Endpoints:                10.12.223.56:8080

Consider a request taking exactly 120s:

# time curl -vkH 'http://myservce:8080/test?timeout=120'
*   Trying 10.15.248.153...
* TCP_NODELAY set
* Connected myservice (10.15.248.153) port 8080 (#0)
...
< HTTP/1.1 200

real    2m0.023s
user    0m0.009s
sys 0m0.009s

This is good. So I configure nginx-ingress timeouts:

nginx.ingress.kubernetes.io/proxy-send-timeout: "900"
nginx.ingress.kubernetes.io/proxy-read-timeout: "900"
nginx.ingress.kubernetes.io/proxy-connect-timeout: "60"

I can confirm it is in the nginx.conf:

proxy_connect_timeout                   60s;
proxy_send_timeout                      900s;
proxy_read_timeout                      900s;

So now, I try enter the nginx ingress pod and try to access myservice via nginx-ingress:

time curl -vkH 'http://127.0.0.1/myservice/test?timeout=120'

But this time I get empty response - sometimes after 35s, sometimes after 90s, but it will get there:

* Curl_http_done: called premature == 0
* Empty reply from server
* Connection #0 to host 127.0.0.1 left intact
curl: (52) Empty reply from server

I have no mored ideas what might be happening. It looks as if the nginx was randomly restarted and my connections were dropped.