Jun 012011
 
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Nginx

I’ve found something interesting in the nginx mailing list today http://forum.nginx.org/read.php?2,202715,202715#msg-202715 . someone asked whether it is possible to block fake user agent such as google bot. sometimes, a lot of bots flood our servers disguise as google bot or other legal bot. Most likely, to scrape our website’s contents. Original google bot always uses the ip address which is owned by Google Inc. Many website owners complained, bad bots only drain their bandwidth usage. 🙂

The first option to use “if” directive in nginx.

if ($http_user_agent ~* "Google Bot") {
	allow 66.x;
	allow 70.x;
	deny all;
}

However, “if” directive considered to be a bad practice when use for anything rather than “return” or “rewrite”. Here’s an example from Igor Sysoev:
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May 312011
 

Sometimes, we prefer to view statistics in graphical form rather than numerical values​​, which is not too attractive to be displayed. Nginx supports stub_status directive module, which we can use to print:

  • Active connections
  • Server accepts handled requests
  • Reading
  • Writing
  • Waiting

For example:

Active connections: 6
server accepts handled requests
 15561 15561 26602
Reading: 4 Writing: 2 Waiting: 0

However, This module is not compiled by default and must be specified using this argument when compiling nginx.

--with-http_stub_status_module

First, to get statistics like the above example, you should modify nginx config file and add location directive this

server {
....
....
	location /nginx_status {
		stub_status on;
		access_log   off;
		allow 1.2.3.4;
		allow 5.6.7.8;
		deny all;
	}
}

perl scripts used to generate statistical images can be downloaded here:

http://kovyrin.net/files/mrtg/rrd_nginx.pl.txt

Rename rrd_nginx.pl.txt to rrd_nginx.pl and make it executable
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