I'm trying to understand why our proxied requests have a much greater chance of significant delay than non-proxied requests.
The server is an 8-core (dual quad) Intel machine. Making requests directly to the nginx backend is just far more reliable. Here's a shell script output that just continuously requests a blank 0k image file from nginx directly on its own port, and spits out a timestamp if the delay isn't 0 or 1 seconds: Thu Mar 5 12:36:17 PST 2009 beginning continuous test of nginx port 8080 Thu Mar 5 12:38:06 PST 2009 Nginx Time is 2 seconds Here's the same test running through haproxy, simultaneously: Thu Mar 5 12:36:27 PST 2009 beginning continuous test of haproxy port 80 Thu Mar 5 12:39:39 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:39:48 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:39:55 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:40:03 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:40:45 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:40:48 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:40:55 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:40:58 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:41:55 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:42:01 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:42:08 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:42:29 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:42:38 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:43:05 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:43:15 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:08 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:25 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:30 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:33 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:39 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:46 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:44:54 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:45:07 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:45:16 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:45:45 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:45:54 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:45:58 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:05 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:08 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:32 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:48 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:53 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:46:58 PST 2009 Nginx Time is 3 seconds Thu Mar 5 12:47:40 PST 2009 Nginx Time is 3 seconds My sanitized haproxy config is here (mongrel backend was omitted for brevity) : http://pastie.org/408729 Are the ACLs just too expensive? Nginx is running with 4 processes, and the box shows mostly idle. top - 21:02:14 up 15 days, 2:47, 4 users, load average: 1.83, 1.59, 1.44 Tasks: 171 total, 2 running, 168 sleeping, 0 stopped, 1 zombie Cpu(s): 11.7%us, 2.7%sy, 0.0%ni, 84.8%id, 0.1%wa, 0.0%hi, 0.7%si, 0.0%st Mem: 8201632k total, 8155856k used, 45776k free, 180244k buffers Swap: 0k total, 0k used, 0k free, 7418644k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 31749 root 20 0 38052 31m 508 S 7 0.4 3:16.78 haproxy 9471 nginx 20 0 14164 2156 748 S 3 0.0 0:21.54 nginx 2555 root 20 0 5880 712 580 S 3 0.0 333:45.38 syslogd 9470 nginx 20 0 14284 2380 740 S 3 0.0 0:26.54 nginx 9469 nginx 20 0 14240 2328 748 S 1 0.0 0:26.20 nginx 5054 root 20 0 99.6m 24m 3188 S 0 0.3 0:12.36 ruby 23699 root 20 0 74828 820 388 R 0 0.0 0:00.01 bash 28744 root 20 0 74696 976 548 S 0 0.0 0:07.27 bash 1 root 20 0 10316 680 568 S 0 0.0 0:10.09 init
