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|
<?php
/**
* 一致性hahs实现类
*
*/
class
FlexiHash{
/**
* var int
* 虚拟节点
*/
private
$_replicas
= 200;
/**
* 使用hash方法
*/
private
$_hasher
= null;
/**
* 真实节点计数器
*
*/
private
$_targetCount
= 0;
/**
* 位置对应节点,用户lookup中根据位置确定要访问的节点
*/
private
$_positionToTarget
=
array
();
/**
* 节点对应位置,用于删除节点
*/
private
$_targetToPositions
=
array
();
/**
* 是否已排序
*/
private
$_positionToTargetSorted
= false;
/**
* @ $hasher hash方法
* @ $replicas 虚拟节点的个数
*
* 确定要使用的hash方法和虚拟的节点数,虚拟节点越多,分布越均匀,但程序的分布式运算越慢
*/
public
function
__construct(FlexiHash_Hasher
$hasher
=null,
$replicas
= null){
// hash方法
$this
->_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));
?>
|
本文转自birdinroom 51CTO博客,原文链接:http://blog.51cto.com/birdinroom/1591823,如需转载请自行联系原作者