There is an nginx server with 2 worker_threads and 500 worker_connections.
I use Apache HTTP benchmarking tool (ab) to create >1500 clients that constantly requests cached data from nginx. In parallel I execute some wget-s and browser sessions with the same request.

After some time nginx starts to refuse connections with clients receiving "connection reset by peer".

Question: is there a way to make nginx return correct "503 Unavailable" errors on high load instead of refusing connections?

Solution is to use HttpLimitZone module (http://wiki.nginx.org/NginxHttpLimitZoneModule) with $host variable.

[code]
http {
limit_zone one $host 10m;
limit_conn one 15;

server {
location /info/ {
limit_conn one 10;
}
location /download/ {
limit_conn one 1;
}
}
}
[/code]