How to check nginx under load?

Question

Nginx

Hello.
There was a task to check how many connections nginx will withstand. As usual I took ab from apache2-utils.
But it was not there, for some reason the test stops. And the tested server is not even loaded by 10%.
Ubuntu 14.04.1 LTS server (both testing and testing).
Firewall turned off.
nginx settings:

user www-data;
worker_processes 2;
pid /run/nginx.pid;
events {
        worker_connections 2048;
        # multi_accept on;
}
http {
        sendfile on;
        tcp_nopush on;
        tcp_nodelay on;
        keepalive_timeout 15;
        types_hash_max_size 2048;
        server_tokens off;
        include /etc/nginx/mime.types;
        default_type application/octet-stream;
        # access_log /var/log/nginx/access.log;
        access_log off;
        error_log /var/log/nginx/error.log;

        gzip on;
        gzip_disable "msie6";

        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;
}

I do the test with the command:
ab -n 10000 -c 100 ">>>URL<<<"
Stably I get the following result:

I.e. once can pass, and then shuts up. Tried different servers. The picture is the same.
Who can prompt in what party to dig? Maybe the host has something like anti-ddos?
DigitalOcean if anything...

Answer 1

yandex-tank.

Answer 2

I support the idea with Yandex tank.
I myself use httperf. At it generation of parallel connections is "more honest" (than in ab). An example of such testing is here: alekciy.livejournal.com/10471.html ("Test Methodology").

Answer 3

worker_processes 2;

At least add more workers

Answer 4

What does netstat show?