前段時間某個需求:客戶提交簡單的表單可以創建一個適應於全終端(PC,Pad,Phone)的刮刮卡活動H5頁面,其中涉及到客戶可在線生成限額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函數來生成UUID(Universally Unique IDentifier,也叫GUID,為全局唯一標識符,是一種由算法生成的唯一標識)來生成。
但當我們用生成1W測試時候,發現生成過些需要幾十秒,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性能測試
<?php xhprof_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秒的時間生成,單次執行需要3969微秒,也就是0.003969秒生成。如果用戶提交表單的同時生成兌換碼,最壞情況下需要4分鐘才給用戶反應,當然可以用訊息隊列異步生成,但是為啥uniqid需要如此多的時間來生成一個簡單的字串呢?
接著去查看uniqid的實作原始碼,程式碼貼在下面
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?但是我們發現生成的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在此為了保持每次生成的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;
最後發現生成1W獎品碼需要39.99587739.995877秒,而usleep間隔時間總和39.982442m,通過打印時間發現通過打印每次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。
最後用了下面程式碼產生獎品碼
/** * 生成兑换码并保存到数据库 返回setNo * $pageId 活动ID * $level 奖品等级 * $numbers 生成奖品的个数 */ public static function generateCDKEYAndSave($pageId,$level,$numbers){ $level1Prefix =array(2,5,9,'E','F','M','N','Q','K','Z');//一等奖的前缀 $level2Prefix =array(1,3,7,'A','C','J','R','U','V','X');//二等奖的前置 $level3Prefix = array(4,6,8,'B','D','G','H','I','L','O','P','R','S','T','W','Y');//三等奖的前缀 if(empty($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); 服务器上面uniqid执行慢的要死 //$code =base_convert(hexdec(md5($pageId.'A#1$v&'.$i)),10,26);//数据过多 hexdec丢失大量精度 $code1 = base_convert(substr(md5($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測試程式碼
#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); }