yii2.0中redis使用过程中踩过的坑（读取redis巨慢） [ 2.0 版本 ]

$startTime = microtime(true);
$rsp = Yii::$app->redis->get($key);
$endTime = microtime(true);
$elapsed = number_format($endTime - $startTime, 4);
echo $elapsed;

在执行读取redis数据的过程中，这个巨慢
执行的结果是2.2772s,平均都要2.2s以上

然后发现在yii里面并没有用到php-redis的扩展
自己写了一个用php-redis的方法来看，

$startTime = microtime(true);
$redis = new Redis();
$redis->connect('127.0.0.1', 6379);
$rsp = $redis->get($key);
$endTime = microtime(true);
$elapsed = number_format($endTime - $startTime, 4);
echo $elapsed;

这个的执行的结果是0.0004s,差别n级别

最后在vendor/yiisoft/yii2-redis/Connection.php 692行中直接return $data

private function parseResponse($command)
{
    $startTime = microtime(true);
    if (($line = fgets($this->_socket)) === false) {
        throw new Exception("Failed to read from socket.\nRedis command was: " . $command);
    }
    $type = $line[0];
    $line = mb_substr($line, 1, -2, '8bit');
    switch ($type) {
        case '+': // Status reply
            if ($line === 'OK' || $line === 'PONG') {
                return true;
            } else {
                return $line;
            }
        case '-': // Error reply
            throw new Exception("Redis error: " . $line . "\nRedis command was: " . $command);
        case ':': // Integer reply
            // no cast to int as it is in the range of a signed 64 bit integer
            return $line;
        case '$': // Bulk replies
            if ($line == '-1') {
                return null;
            }
            $length = (int)$line + 2;
            $data = '';
            while ($length > 0) {
                if (($block = fread($this->_socket, $length)) === false) {
                    throw new Exception("Failed to read from socket.\nRedis command was: " . $command);
                }
                $data .= $block;
                $length -= mb_strlen($block, '8bit');
            }

            $endTime = microtime(true);
            $elapsed = number_format($endTime - $startTime, 4);
            echo $elapsed;
            return $data;
            return mb_substr($data, 0, -2, '8bit');
        case '*': // Multi-bulk replies
            $count = (int) $line;
            $data = [];
            for ($i = 0; $i < $count; $i++) {
                $data[] = $this->parseResponse($command);
            }

            return $data;
        default:
            throw new Exception('Received illegal data from redis: ' . $line . "\nRedis command was: " . $command);
    }
}

这里的耗时是0.0017s，所以定位的问题是在下面这行代码中

return mb_substr($data, 0, -2, '8bit');

最后，发现是php的mb_string的扩展没有装（好奇怪，没装这个还能用这个mb_substr函数，还能获得正确的结果);
安装这个扩展sudo apt-get install php7.0-mbstring。
再访问，耗时0.0012s，问题解决