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);
}
