为了测试边缘负载均衡的限流策略，需要灵活的调整真实服务器的 TPS，把 Nginx 配置成一个假负载，可以通过 url 参数 s 传值给 ngx.sleep() 控制后端的响应时间。测试方式：curl http://localhost:80/mock/sleep?s=2

localhost.conf

server {
	listen       80 backlog=4096 reuseport;
	server_name  localhost;
	index        index.html;
	root         /opt/case/null/;
	access_log   off;

	location /status {
		stub_status on;
		allow 127.0.0.1;
		deny all;
	}

	location ^~ /mock/sleep {
		content_by_lua_block {
			require "resty.core"
			local arg = ngx.req.get_uri_args()
			for k,v in pairs(arg) do
				if (k == "s" and tonumber(v) <= 60) then
					ngx.sleep(v)
					ngx.header["Content-type"] = "text/plain";
					ngx.say("Have been sleeping for ", v, " seconds.")
				else
					ngx.header["Content-type"] = "text/plain";
					ngx.say("The value of arguments must be 0.001 ~ 60.")
					ngx.say('Usage:')
					ngx.say('  curl http://localhost:80/mock/sleep?s=2')
				end 
			end 
		}    
	}
}

server {
	listen    80  default_server;
	return    403;

	##. Redirect all HTTP requests to HTTPS with a 301 Moved Permanently response.
	#return 301 https://$host$request_uri;
}

为了防止有人捣蛋，URI 参数 s 的取值范围是 0.001 ~ 60，如果觉得不合适，修改 if 语句的检查条件即可。ngx.sleep() 的单位是秒，精度是毫秒，更多信息请参考：
https://github.com/openresty/lua-nginx-module#ngxsleep
https://moonbingbing.gitbooks.io/openresty-best-practices/ngx_lua/sleep.html
https://blog.cloudflare.com/a-question-of-timing/

测试范例：

# » curl --silent -o /dev/null \
-w "\n\n#-- DNS Lookup --\ntime_namelookup\t: %{time_namelookup}\n\n#-- TCP Handshake --\ntime_connect\t: %{time_connect}\n\n#-- SSL Handshake --\ntime_appconnect\t: %{time_appconnect}\n\ntime_pretransfer\t: %{time_pretransfer}\n#-- Wait Server Response --\ntime_starttransfer\t: %{time_starttransfer}\ntime_redirect\t: %{time_redirect}\n\n#-- Data Transfer --\ntime_total\t: %{time_total}\n" \
'http://localhost:80/mock/sleep?s=2'


#-- DNS Lookup --
time_namelookup : 0.004

#-- TCP Handshake --
time_connect    : 0.004

#-- SSL Handshake --
time_appconnect : 0.000

time_pretransfer        : 0.004
#-- Wait Server Response --
time_starttransfer      : 2.007
time_redirect   : 0.000

#-- Data Transfer --
time_total      : 2.007