_hasher = $hasher?$hasher: new FlexiHash_Crc32Hasher();
// 虚拟节点的个数
if (!empty($replicas)){
$this->_replicas = $replicas;
}
}
/**
* 增加节点，根据虚拟节点数，把节点分布到更多的虚拟位置上
*/
public function addTarget($target){
if (isset($this->_targetToPositions[$target])) {
throw new FlexiHash_Exception("Target $target already exists.");
}
$this->_targetToPositions[$target] = array();
for ($i = 0; $i < $this->_replicas; $i++) {
// 根据规定的方法hash
$position = $this->_hasher->hash($target.$i);
// 虚拟节点对应的真实的节点
$this->_positionToTarget[$position] = $target;
// 真实节点包含的虚拟节点
$this->_targetToPositions[$target][] = $position;
}
$this->_positionToTargetSorted = false;
// 真实节点个数
$this->_targetCount++;
return $this;
}
/**
* 添加多个节点
*
*/
public function addTargets($targets){
foreach ($targets as $target){
$this->addTarget($target);
}
return $this;
}
/**
* 移除某个节点
*
*/
public function removeTarget($target){
if (!isset($this->_targetToPositions[$target])){
throw new FlexiHash_Exception("target $target does not exist\n");
}
foreach($this->_targetToPositions[$target] as $position){
unset($this->_positionToTarget[$position]);
}
unset($this->_targetToPositions[$target]);
$this->_targetCount--;
return $this;
}
/**
* 获取所有节点
*
*/
public function getAllTargets(){
return array_keys($this->_targetToPositions);
}
/**
* 根据key查找hash到的真实节点
*
*/
public function lookup($resource){
$targets = $this->lookupList($resource, 1);
if (empty($targets)){
throw new FlexiHash_Exception("no targets exist");
}
return $targets[0];
}
/**
* 查找资源存在的节点
*
* 描述:根据要求的数量，返回与$resource哈希后数值相等或比其大并且是最小的数值对应的节点，若不存在或数量不够，则从虚拟节点排序后的前一个或多个
*/
public function lookupList($resource, $requestedCount){
if (!$requestedCount) {
throw new FlexiHash_Exception('Invalid count requested');
}
if (empty($this->_positionToTarget)) {
return array();
}
// 直接节点只有一个的时候
if ($this->_targetCount == 1 ){
return array_unique(array_values($this->_positionToTarget));
}
// 获取当前key进行hash后的值
$resourcePosition = $this->_hasher->hash($resource);
$results = array();
$collect = false;
$this->_sortPositionTargets();
// 查找与$resourcePosition 相等或比其大并且是最小的数
foreach($this->_positionToTarget as $key => $value){
if (!$collect && $key > $resourcePosition){
$collect = true;
}
if ($collect && !in_array($value, $results)){
$results[] = $value;
}
// 找到$requestedCount 或个数与真实节点数量相同
if (count($results) == $requestedCount || count($results) == $this->_targetCount){
return $results;
}
}
// 如数量不够或者未查到，则从第一个开始，将$results中不存在前$requestedCount-count($results)，设置为需要的节点
foreach ($this->_positionToTarget as $key => $value){
if (!in_array($value, $results)){
$results[] = $value;
}
if (count($results) == $requestedCount || count($results) == $this->_targetCount){
return $results;
}
}
return $results;
}
/**
* 根据虚拟节点进行排序
*/
private function _sortPositionTargets(){
if (!$this->_positionToTargetSorted){
ksort($this->_positionToTarget, SORT_REGULAR);
$this->_positionToTargetSorted = true;
}
}
}// end class
/**
* hash方式
*/
interface FlexiHash_Hasher{
public function hash($string);
}
class FlexiHash_Crc32Hasher implements FlexiHash_Hasher{
public function hash($string){
return sprintf("%u",crc32($string));
}
}
class FlexiHash_Md5Hasher implements FlexiHash_Hasher{
public function hash($string){
return substr(md5($string), 0, 8);
}
}
class FlexiHash_Exception extends Exception{
}
$runData['BEGIN_TIME'] = microtime(true);
$key="lihuibin";
for($i=0;$i<10;$i++) {
$targetsArray = array(
"127.0.0.1:11211",
"127.0.0.1:11212",
"127.0.0.1:11213",
"127.0.0.1:11214",
#"127.0.0.1:11218"
);
$flexiHashObj = new FlexiHash(new FlexiHash_Crc32Hasher(),1);
$result = $flexiHashObj->addTargets($targetsArray);
$key=$key."$i";
$targets = $flexiHashObj->lookup($key);
var_dump($targets);
#$key = md5(mt_rand());
#$targets = $flexiHashObj->lookup($key);
#var_dump($targets);
}
echo "一致性hash:";
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
exit;
$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);
}
echo "单台机器:";
var_dump(number_format(microtime(true) - $runData['BEGIN_TIME'],6));
?>
文章名称：phpmemcached一致性hash
网页链接：
http://bjjierui.cn/article/gijdcp.html
