This module is not distributed with the Nginx source. Installation instructions are Installation below.
The upstream_hash module provides simple upstream load distribution by hashing a configurable variable (e.g., the request URI, incoming HTTP headers, or some combination). Example usage:
Here, Nginx will choose server1 or server2 by hashing the request URI ($request_uri).
syntax hash $variable
Enables upstream hashing of $variable.
When present, the "server" directives cannot take any arguments ("weight", "max_fails", etc.).
syntax hash_again number
Number of times to rehash the value and choose a different server if the backend connection fails. Increase this number to provide high availability.
After extracting, you will need to patch the latest Nginx source (0.7.62 as of this writing). Run patch like this:
cd nginx-0.7.62 # or whatever patch -p0 < /path/to/upstream/hash/directory/nginx.patch
Then add the following option to your Nginx ./configure command:
Then "make" and "make install" as usual.
 The hash algorithm
As of 0.3, the hash algorithm and the failover algorithm use a CRC-32 computation compatible with PECL Memcache.
- . * 0.3.1: Updated patch to work with latest Nginx sources
- . * 0.3: Feature: PECL Memcache compatibility. Change: Removed "hash_method" directive.
Send bug reports to Evan Miller .