[edit] Synopsis

ngx_http_split_clients_module is used to split clients based on some conditions(e.g ip addresses, headers, cookies, etc).

[edit] Examples

[edit] Basic configuration:

http {
    split_clients "${remote_addr}AAA" $variant {
        40.5% ".one";
        59.5% ".two";
    }
 
    server {
        location / {
             index index${variant}.html;
        [...]
    }

On the sample configuration above, the input for calculating the percentage is the variable plus string ("${remote_addr}AAA"). The value of this string is hashed using MurmurHash2 (which will generate a 32bit integer). In the example given:

• Hash values from 0 to 1739461754 (40.5%) will set the $variant variable with the value ".one" and will try to load the file "index.one.html";
• Hash values from 1739461755 to 4294967295 (59.5%) will set the $variant variable with the value ".two" and will try to load the file "index.two.html";

[edit] Sending a query string variable to 51% of clients (to PHP scripts)

http {
    split_clients "${remote_addr}" $additionalQsVariable {
	    51% "coolVariable=1";
	    49% "";
	}
 
    server {
        location ~ \.php$ {
            set $args "${query_string}&${additionalQsVariable}";
            [...]
        }
    }

[edit] Redirecting 51% of the traffic to another URL

http {
    split_clients "${remote_addr}" $redirectSite {
	    51% "1";
	    49% "0";
	}
 
    server {
        location / {
            if ($redirectSite = "1") {
                return 302 "http://www.website2.com/";
            }
            [...]
        }
    }

• Although on nginx IF is evil, we can use it in this specific case.

[edit] Appendix

Instead of ${remote_addr}, one could use ${cookie}, ${args} or any other nginx variable. You may also add a salt (arbitrary string) if you wish.

• Keep in mind that if you use a variable like ${remote_addr} (user IP), the hash (and percentage) will always be the same as long as the user/client keep the same IP. In other words, the $variant value will always be the same for the same IP.
• Hashing algorithm is MurmurHash2 since version 1.0.1; Previously CRC32.

[edit] Directives

[edit] split_clients

[edit] References

• Original Documentation
• Naming convention discussion