ngx_upstream_problem.conf

events {
    worker_connections  1024;
}

http {
    upstream xx {
        server 127.0.0.1:8003;
        server 127.0.0.1:8003;
    }
    server {
        listen       8003;
        return 444;
    }
    server {
        listen       8002;
        location = /t {
            proxy_pass http://xx;
        }
    }
}

# the request will wait for ever
# curl -sv 127.0.0.1:8002/t