使用php实现权重轮询调度算法

[lovecn]

//权重轮询调度算法类http://www.36nu.com/post/145.html
class WeightedRoundRobin
{
private static $_weightArray = array();

private static $_i = -1;//代表上一次选择的服务器
private static $_gcd;//表示集合S中所有服务器权值的最大公约数
private static $_cw = 0;//当前调度的权值
private static $_max;
private static $_n;//agent个数

public function __construct(array $weightArray)
{
    self::$_weightArray = $weightArray;
    self::$_gcd = self::getGcd(self::$_weightArray);
    self::$_max = self::getMaxWeight(self::$_weightArray);
    self::$_n = count($weightArray);
}

private static function getGcd(array $weightArray)
{
    $temp = array_shift($weightArray);
    $min = $temp['weight'];
    $status = false;
    foreach ($weightArray as $val) {
        $min = min($val['weight'], $min);
    }

    if ($min == 1) {
        return 1;
    } else {

        for ($i = $min; $i > 1; $i--) {

            foreach ($weightArray as $val) {
                if (is_int($val['weight'] / $i)) {
                    $status = true;
                } else {
                    $status = false;
                    break;
                }
            }
            if ($status) {
                return $i;
            } else {
                return 1;
            }

        }
    }

}

private static function getMaxWeight(array $weightArray)
{
    if (empty($weightArray)) {
        return false;
    }
    $temp = array_shift($weightArray);
    $max = $temp['weight'];
    foreach ($weightArray as $val) {
        $max = max($val['weight'], $max);
    }
    return $max;
}

public function getWeight()
{

    while (true) {

        self::$_i = ((int)self::$_i + 1) % (int)self::$_n;

        if (self::$_i == 0) {

            self::$_cw = (int)self::$_cw - (int)self::$_gcd;
            if (self::$_cw <= 0) {
                self::$_cw = (int)self::$_max;

                if (self::$_cw == 0) {
                    return null;
                }
            }
        }

        if ((int)(self::$_weightArray[self::$_i]['weight']) >= self::$_cw) {
            return self::$_weightArray[self::$_i];
        }
    }
}

}

//测试代码
$arr = array(
array('id' => 'A', 'weight' => 3),
array('id' => 'B', 'weight' => 3),
array('id' => 'C', 'weight' => 6),
array('id' => 'D', 'weight' => 4),
array('id' => 'E', 'weight' => 1),

);
$weight = new WeightedRoundRobin($arr);

$a=0;
$b=0;
$c=0;
$d=0;
$e=0;
for ($j = 0; $j < 100; $j++) {
$weightInfo = $weight->getWeight();
echo $weightInfo['id'].'----------------------weight:'.$weightInfo['weight'].'
';
if($weightInfo['id'] == 'A'){
$a++;
}
if($weightInfo['id'] == 'B'){
$b++;
}
if($weightInfo['id'] == 'C'){
$c++;
}
if($weightInfo['id'] == 'D'){
$d++;
}
if($weightInfo['id'] == 'E'){
$e++;
}
}
echo 'A:'.$a.'
';
echo 'B:'.$b.'
';
echo 'C:'.$c.'
';
echo 'D:'.$d.'
';
echo 'E:'.$e.'
';