如题分享一老外实现思路，抛开redis自身配置主从外模拟memcache中hash多服务器承载

原文https://github.com/jdp/redisent/blob/master/redisent_cluster.php

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php
/**
* Redisent, a Redis interface for the modest
* @author Justin Poliey
* @license http://www.opensource.org/licenses/mit-license.php The MIT License
* @package Redisent
*/
require \'redisent.php\';
/**
* A generalized Redisent interface for a cluster of Redis servers
*/
class RedisentCluster {
/**
* Collection of Redisent objects attached to Redis servers
* @var array
* @access private
*/
private $redisents;
/**
* Aliases of Redisent objects attached to Redis servers, used to route commands to specific servers
* @see RedisentCluster::to
* @var array
* @access private
*/
private $aliases;
/**
* Hash ring of Redis server nodes
* @var array
* @access private
*/
private $ring;
/**
* Individual nodes of pointers to Redis servers on the hash ring
* @var array
* @access private
*/
private $nodes;
/**
* Number of replicas of each node to make around the hash ring
* @var integer
* @access private
*/
private $replicas = 128;
/*** 特殊方法默认到特定连接
* The commands that are not subject to hashing
* @var array
* @access private
*/
private $dont_hash = array(
\'RANDOMKEY\', \'DBSIZE\',
\'SELECT\', \'MOVE\', \'FLUSHDB\', \'FLUSHALL\',
\'SAVE\', \'BGSAVE\', \'LASTSAVE\', \'SHUTDOWN\',
\'INFO\', \'MONITOR\', \'SLAVEOF\'
);
/**
* Creates a Redisent interface to a cluster of Redis servers
* @param array $servers The Redis servers in the cluster. Each server should be in the format array(\'host\' => hostname, \'port\' => port)
*/
function __construct($servers) {
$this->ring = array();
$this->aliases = array();
foreach ($servers as $alias => $server) {
$this->redisents[] = new Redisent($server[\'host\'], $server[\'port\']);
if (is_string($alias)) {
$this->aliases[$alias] = $this->redisents[count($this->redisents)-1];
}
for ($replica = 1; $replica <= $this->replicas; $replica++) {
$this->ring[crc32($server[\'host\'].\':\'.$server[\'port\'].\'-\'.$replica)] = $this->redisents[count($this->redisents)-1];
}
}
ksort($this->ring, SORT_NUMERIC);
$this->nodes = array_keys($this->ring);
}
/**
* Routes a command to a specific Redis server aliased by {$alias}.
* @param string $alias The alias of the Redis server
* @return Redisent The Redisent object attached to the Redis server
*/
function to($alias) {
if (isset($this->aliases[$alias])) {
return $this->aliases[$alias];
}
else {
throw new Exception(\"That Redisent alias does not exist\");
}
}
/* Execute a Redis command on the cluster */
function __call($name, $args) {
/* Pick a server node to send the command to */
$name = strtoupper($name);
if (!in_array($name, $this->dont_hash)) {
$node = $this->nextNode(crc32($args[0]));
$redisent = $this->ring[$node];
}
else {
$redisent = $this->redisents[0];
}
/* Execute the command on the server */
return call_user_func_array(array($redisent, $name), $args);
}
/*** 2分法查找
* Routes to the proper server node
* @param integer $needle The hash value of the Redis command
* @return Redisent The Redisent object associated with the hash
*/
private function nextNode($needle) {
$haystack = $this->nodes;
while (count($haystack) > 2) {
$try = floor(count($haystack) / 2);
if ($haystack[$try] == $needle) {
return $needle;
}
if ($needle < $haystack[$try]) {
$haystack = array_slice($haystack, 0, $try + 1);
}
if ($needle > $haystack[$try]) {
$haystack = array_slice($haystack, $try + 1);
}
}
return $haystack[count($haystack)-1];
}
}

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