最近在看一些分布式方面的文章，所以就用php实现一致性hash来练练手，以前一般用的是最原始的hash取模做 分布式，当生产过程中添加或删除一台memcache都会造成数据的全部失效，一致
<?php
/**
* memcache一致性hash的php实现方法
*/
class memcacheHashMap {
private $_node = array();
private $_nodeData = array();
private $_keyNode = 0;
private $_memcache = null;
//每个物理服务器生成虚拟节点个数 [注：节点数越多，cache分布的均匀性越好，同时set get操作时，也更耗资源，10台物理服务器，采用200较为合理]
private $_virtualNodeNum = 200;
private function __construct() {
$config = array(//五个memcache服务器
'127.0.0.1:11211',
'127.0.0.1:11212',
'127.0.0.1:11213',
'127.0.0.1:11214',
'127.0.0.1:11215'
);
if (!$config) throw new Exception('Cache config NULL');
foreach ($config as $key => $value) {
for ($i = 0; $i < $this->_virtualNodeNum; $i++) {
$this->_node[sprintf("%u", crc32($value . '_' . $i))] = $value . '_' . $i;//循环为每个memcache服务器创建200个虚拟节点
}
}
ksort($this->_node);//创建出来的1000个虚拟节点按照键名从小到大排序
}
//实例化该类
static public function getInstance() {
static $memcacheObj = null;
if (!is_object($memcacheObj)) {
$memcacheObj = new self();
}
return $memcacheObj;
}
//根据传来的键查找到对应虚拟节点的位置
private function _connectMemcache($key) {
$this->_nodeData = array_keys($this->_node);//所有的虚拟节点的键的数组
$this->_keyNode = sprintf("%u", crc32($key));//算出键的hash值
$nodeKey = $this->_findServerNode();//找出对应的虚拟节点
//如果超出环，从头再用二分法查找一个最近的，然后环的头尾做判断，取最接近的节点
if ($this->_keyNode > end($this->_nodeData)) {
$this->_keyNode -= end($this->_nodeData);
$nodeKey2 = $this->_findServerNode();
if (abs($nodeKey2 - $this->_keyNode) < abs($nodeKey - $this->_keyNode)) $nodeKey = $nodeKey2;
}
var_dump($this->_node[$nodeKey]);
list($config, $num) = explode('_', $this->_node[$nodeKey]);
if (!$config) throw new Exception('Cache config Error');
if (!isset($this->_memcache[$config])) {
$this->_memcache[$config] = new Memcache;
list($host, $port) = explode(':', $config);
$this->_memcache[$config]->connect($host, $port);
}
return $this->_memcache[$config];
}
//二分法根据给出的值找出最近的虚拟节点位置
private function _findServerNode($m = 0, $b = 0) {
$total = count($this->_nodeData);
if ($total != 0 && $b == 0) $b = $total - 1;
if ($m < $b){
$avg = intval(($m+$b) / 2);
if ($this->_nodeData[$avg] == $this->_keyNode) return $this->_nodeData[$avg];
elseif ($this->_keyNode < $this->_nodeData[$avg] && ($avg-1 >= 0)) return $this->_findServerNode($m, $avg-1);
else return $this->_findServerNode($avg+1, $b);
}
if (abs($this->_nodeData[$b] - $this->_keyNode) < abs($this->_nodeData[$m] - $this->_keyNode)) return $this->_nodeData[$b];
else return $this->_nodeData[$m];
}
public function set($key, $value, $expire = 0) {
return $this->_connectMemcache($key)->set($key, json_encode($value), 0, $expire);
}
public function add($key, $value, $expire = 0) {
return $this->_connectMemcache($key)->add($key, json_encode($value), 0, $expire);
}
public function get($key) {
return json_decode($this->_connectMemcache($key)->get($key), true);
}
public function delete($key) {
return $this->_connectMemcache($key)->delete($key);
}
}
$runData['BEGIN_TIME'] = microtime(true);
//测试一万次set加get
for($i=0;$i<10000;$i++) {
$key = md5(mt_rand());
$b = memcacheHashMap::getInstance()->set($key, time(), 10);
}
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
$runData['BEGIN_TIME'] = microtime(true); $m= new Memcache;
$m->connect('127.0.0.1', 11211);
for($i=0;$i<10000;$i++) {
$key = md5(mt_rand());
$b = $m->set($key, time(), 0, 10);
}
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
?>