thanks for the fast reply, Maxim
the code is complicated and i cannot send it all.
more info: when i set the proxy_connect_timeout from default 60s to 2s (the upstream server is close enough) , i could see that in the hang state, all workers were waiting for an answer from the upstream server (thru the proxy) and after that the nginx hanged (so lack of resources also occurs after the timeout)

any suggestions ?
tnx
Gad