Nginx Series Tutorials: HTTP upstream Request Hash module

Ngx_http_upstream_hash_module

This module is provided by a third party and is not included in the Nginx source release version.

Upstream_hash This module provides a simple upstream load allocation by hashing a configurable variable (for example, a request URI, an incoming HTTP header, or some combination). Examples of usage are as follows:

Here, Nginx selects Server1 or Server2 by the URI ($ request_uri) of the hash request.

Instructions

Template:anchor

Hash

Syntax: Hash $variable
Scope: Upstream
Enables hashing of upstream $variable variables.
Currently, the server directive cannot execute any parameters ("weight", "max_fails", etc.).
Template:anchor

Hash_method

Syntax: Hash_method [CRC32 | simple]
Default value: Simple
Scope: Upstream
The hash algorithm uses "CRC32" to take the last 15 bits of the CRC32 value and is calculated by the number of servers. (This behavior is compatible with Libmemcache.) As described below, "the" simple "hash Algorithm".
Template:anchor

Hash_again

Syntax: Hash_again number
Default value: 0
Scope: Upstream
If the backend connection fails, the value is processed in the amount of time and a different server is selected. Increase the number to provide high availability.
Template:anchor

Installation

The module is not a nginx source distribution. You can download the Request_hash module here: nginx_upstream_hash-0.2.tar.gz.

After decompression, you will need to patch to the latest Nginx source (0.5.21 version). Run the patch as follows:

Then add the following options to your nginx./configure command:

Then, run "make" and "make install" normally.

Template:anchor

The "simple" hash Algorithm

The "simple" hash algorithm is the same as used in the Nginx internal hash table. This feature is:

The hash value is modulo ' d of the number of selected servers. A server index can be determined by the order in which it appears in the upstream block.