PHP uniqid函數執行緩慢的問題

前段時間某個需求：客戶提交簡單的表單可以建立一個適應於全終端（PC，Pad，Phone）的刮刮卡活動H5頁面，其中涉及到客戶可線上產生限額6W獎品碼的功能。
因為需要保持每個活動獎品碼的唯一，我們先是準備用PHP的uniqid函數來產生UUID（Universally Unique IDentifier，也叫GUID，為通用唯一識別碼，是一種由演算法產生的唯一標識）來產生。
但當我們用產生1W測試時候，發現產生過些需要幾十秒，還不包括插入至資料庫的時間，然後用xhprof寫了個簡單例子進行效能測試

<?phpxhprof_enable(XHPROF_FLAGS_CPU|XHPROF_FLAGS_MEMORY);function   myfunc(){    for($i=0;$i<10000;$i++){        $data = uniqid();    }}myfunc();$data = xhprof_disable();print_r($data);

測試結果：

[myfunc==>uniqid] => Array(            [ct] => 10000            [wt] => 39975062            [cpu] => 0            [mu] => 960752            [pmu] => 0)

竟然需要接近40秒的時間產生，單次執行需要3969微秒，也即是0.003969秒產生。如果使用者提交表單的同時產生兌換碼，最壞情況下需要4分鐘才給使用者反應，當然可以用訊息佇列非同步產生，但是為啥uniqid需要如此多的時間來產生一個簡單的字串呢？

然後去查看uniqid的實現源碼，代碼貼在下面

PHP_FUNCTION(uniqid){     char *prefix = "";#if defined(__CYGWIN__)     zend_bool more_entropy = 1;#else     zend_bool more_entropy = 0;#endif     char *uniqid;     int sec, usec, prefix_len = 0;     struct timeval tv;     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "|sb", &prefix, &prefix_len,                                     &more_entropy)) {          return;     }#if HAVE_USLEEP && !defined(PHP_WIN32)     if (!more_entropy) {#if defined(__CYGWIN__)          php_error_docref(NULL TSRMLS_CC, E_WARNING, "You must use 'more entropy' under CYGWIN");          RETURN_FALSE;#else          usleep(1);#endif     }#endif     gettimeofday((struct timeval *) &tv, (struct timezone *) NULL);     sec = (int) tv.tv_sec;     usec = (int) (tv.tv_usec % 0x100000);     /* The max value usec can have is 0xF423F, so we use only five hex     * digits for usecs.     */     if (more_entropy) {          spprintf(&uniqid, 0, "%s%08x%05x%.8F", prefix, sec, usec, php_combined_lcg(TSRMLS_C) * 10);     } else {          spprintf(&uniqid, 0, "%s%08x%05x", prefix, sec, usec);     }     RETURN_STRING(uniqid, 0);}

看邏輯也沒有複雜的操作，也是對現在時間秒和微秒進行簡單的處理，然後寫了個簡單的測試

int getUniqid( char * uid) {     int sec, usec;     struct timeval tv;     gettimeofday(( struct timeval *) &tv, ( struct timezone *) NULL);     sec = ( int) tv. tv_sec;     usec = ( int ) (tv.tv_usec % 0x100000);     sprintf(uid, "%08x%05x" , sec, usec);     return 1;}

執行1W次也就需要2000微秒，這又是為啥？但是我們發現產生的uid中存在大量的重複，這是才注意點原代碼中的usleep函數，
加上usleep函數在測試，這次和PHP結果一致也需要將近40秒，usleep在此為了保持每次產生的uid不同。
那問題出現在usleep函數上了，然後在usleep前後加上取間隔時間，代碼如下

struct timeval start, end;      gettimeofday(( struct timeval *) &start, ( struct timezone *) NULL);      usleep(1);      gettimeofday(( struct timeval *) &end, ( struct timezone *) NULL);      unsigned long space = (end.tv_sec - start. tv_sec) * 1000000 + end.tv_usec              - start. tv_usec;       spaceCost += space;

最後發現產生1W獎品碼需要39.99587739.995877秒，而usleep間隔時間總和39.982442m，通過列印usleep時間發現每次usleep(1)從進程掛起到喚醒需要4000微秒,本來就知道usleep達不到精度，也也相差太遠了點。
最後用了下面代碼產生獎品碼

/**     * 產生兌換碼並儲存到資料庫  返回setNo     * $pageId 活動ID     * $level 獎品等級     * $numbers 產生獎品的個數     */    public static  function generateCDKEYAndSave($pageId,$level,$numbers){        $level1Prefix =array(2,5,9,'E','F','M','N','Q','K','Z');//一等獎的首碼        $level2Prefix =array(1,3,7,'A','C','J','R','U','V','X');//二等獎的前置        $level3Prefix = array(4,6,8,'B','D','G','H','I','L','O','P','R','S','T','W','Y');//三等獎的首碼        if(empty($pageId) || empty($level) || empty($numbers)) return false;        $levelPrefix =$level1Prefix;        if($level==2) $levelPrefix = $level2Prefix;        if($level==3) $levelPrefix = $level3Prefix;        $codes =array();        $now = time();        for($i=0;$i<$numbers;$i++){            $prefixKey = array_rand($levelPrefix);            $prefix = self::COUPON_PREFIX.$levelPrefix[$prefixKey];            //$code =base_convert(hexdec(md5(uniqid())),10,26); 伺服器上面uniqid執行慢的要死            //$code =base_convert(hexdec(md5($pageId.'A#1$v&'.$i)),10,26);//資料過多 hexdec丟失大量精度            $code1 = base_convert(substr(md5($pageId.$i.$now), 0, 10), 16, 36);            $code2 = base_convert($i, 10, 26);            $code2Len = strlen($code2);            if ($code2Len == 1) {                $code2 .= chr(rand(82, 90)) . chr(rand(82, 90)) . chr(rand(82, 90));            }            else if ($code2Len == 2) {                $code2 .= chr(rand(82, 90)) . chr(rand(82, 90));            }            else if ($code2Len == 3) {                $code2 .= chr(rand(82, 90));            }            $code =$code1.$code2;            $codes[] = $prefix.strtoupper($code);        }       return $codes;    }

附帶uuid測試代碼

#include <stdio.h>#include <malloc.h>#include <sys/time.h>#include <unistd.h>unsigned long sleepCost = 0;int getUniqid( char * uid,int times) {      struct timeval start, end;      gettimeofday(( struct timeval *) &start, ( struct timezone *) NULL);      usleep(1);      gettimeofday(( struct timeval *) &end, ( struct timezone *) NULL);      unsigned long space = (end.tv_sec - start. tv_sec) * 1000000 + end.tv_usec              - start. tv_usec;     sleepCost += space;      if (0 == times%1000) printf ("\n-----sleep cost-------\n%lu usec\n", space);      int sec, usec;      struct timeval tv;      gettimeofday(( struct timeval *) &tv, ( struct timezone *) NULL);     sec = ( int) tv. tv_sec;     usec = ( int ) (tv.tv_usec % 0x100000);      sprintf(uid, "%08x%05x" , sec, usec);      return 1;}int main( int argc, char * argv[]) {      struct timeval start, end;      gettimeofday(( struct timeval *) &start, ( struct timezone *) NULL);      for ( int i = 1; i <= 10000; i++) {           char data[20];          getUniqid(data,i);     }      gettimeofday(( struct timeval *) &end, ( struct timezone *) NULL);      unsigned long space = (end.tv_sec - start. tv_sec) * 1000000 + end.tv_usec              - start. tv_usec;      printf( "\n-----cost-------\n% lu usec\n  \n-----sum sleep sost-------\n% lu usec\n" , space,sleepCost);}

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