[转]Nginx hash Module

逃离我推掉我的手 2022-08-27 11:39 103阅读 0赞

导读：  
  
　　本模块由第三方提供，不包含在 Nginx 的源码发布版中。安装介绍等请看 这里.  
  
　　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:  
  
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　　upstream backend \{  
  
server server1;  
  
server server2;  
  
hash $request\_uri;  
  
\}  
  
  
  
　　Here, Nginx will choose server1 or server2 by hashing the request URI ($request\_uri).  
  
　　指令  
  
　　hash  
  
　　hash\_method  
  
　　hash\_again  
  
　　hash  
  
　　语法： hash $variable  
  
　　作用域： upstream  
  
　　Enables upstream hashing of $variable.  
  
　　When present, the "server" directives cannot take any arguments ("weight", "max\_fails", etc.).  
  
　　hash\_method  
  
　　语法： hash\_method \[ crc32 | simple \]  
  
　　默认值： simple  
  
　　作用域： upstream  
  
　　The hash algorithm to use. "crc32" takes the last 15 bits of the crc32 value and modulo's by the number of servers. (This behavior is compatible with libmemcache.) "simple" is described below.  
  
　　hash\_again  
  
　　语法： hash\_again number  
  
　　默认值： 0  
  
　　作用域： upstream  
  
　　Number of times to rehash the value and choose a different server if the backend connection fails. Increase this number to provide high availability.  
  
　　Installation  
  
　　This module is not distributed with the Nginx source. You can download the request\_hash module here: nginx\_upstream\_hash-0.2.tar.gz  
  
　　After extracting, you will need to patch the latest Nginx source (0.5.21 as of this writing). Run patch like this:  
  
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　　cd nginx-0.5.21  
  
patch -p0  
  
  
　　Then add the following option to your Nginx ./configure command:  
  
　　1 --add-module=path/to/upstream/hash/directory  
  
  
  
　　Then "make" and "make install" as usual.  
  
　　The "simple" hash algorithm  
  
　　The "simple" hash algorithm is the same as that used for Nginx's internal hash tables. The function is:  
  
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　　\#define ngx\_hash(key, c) ((u\_int) key \* 31 + c)  
  
  
  
u\_int ngx\_hash\_key(u\_char \*data, size\_t len)  
  
\{  
  
u\_int i, key;  
  
  
  
key = 0;  
  
  
  
**for**(i = 0; i  
key \*= 31;  
  
key += data\[i\];  
  
\}  
  
  
  
**return**key;  
  
\}  
  
  
  
　　The hash value is then modulo'd by the number of servers, and thus a server is picked. A server's index is determined by the order in which it appears in the upstream block.  
  
  
  
本文转自  
  
[http://anotherbug.blog.chinajavaworld.com/entry/4298/0/][http_anotherbug.blog.chinajavaworld.com_entry_4298_0]

[http_anotherbug.blog.chinajavaworld.com_entry_4298_0]: http://anotherbug.blog.chinajavaworld.com/entry/4298/0/