我一定遗漏了一些关于 PHP/Symfony 如何处理并发请求的信息，或者可能如何处理数据库上的潜在并发查询......

这段代码似乎在做不可能的事情 - 它随机（大约每月一次）在底部创建新实体的副本。我的结论是，当两个客户端两次发出相同的请求，并且两个线程同时执行 SELECT 查询，选取 stop == NULL 的条目，然后它们都（？）设置该条目的停止时间时，一定会发生这种情况，他们都写了一个新条目。

据我所知，这是我的逻辑大纲：

1. 获取所有停止时间为 NULL 的条目
2. 循环这些条目
3. 仅当输入日期 (UTC) 与当前日期 (UTC) 不同时才继续
4. 将打开条目的停止时间设置为 23:59:59 并刷新到数据库
5. 构建一个新条目，开始时间为第二天的 00:00:00
6. 断言该位置没有其他未结条目
7. 断言该位置没有未来的条目
8. 只有这样 - 将新条目刷新到数据库

控制器自动关闭和打开

//if entry spans daybreak (midnight) close it and open a new entry at the beginning of next day
private function autocloseAndOpen($units) {

    $now = new \DateTime("now", new \DateTimeZone("UTC"));

    $repository = $this->em->getRepository('App\Entity\Poslog\Entry');
    $query = $repository->createQueryBuilder('e')
    ->where('e.stop is NULL')
        ->getQuery();
    $results = $query->getResult(); 

    if (!isset($results[0])) {
        return null; //there are no open entries at all
    }

    $em = $this->em;
    $messages = "";

    foreach ($results as $r) {
        if ($r->getPosition()->getACRGroup() == $unit) { //only touch the user's own entries

            $start = $r->getStart();

            //Assert entry spanning datebreak
            $startStr = $start->format("Y-m-d"); //Necessary for comparison, if $start->format("Y-m-d") is put in the comparison clause PHP will still compare the datetime object being formatted, not the output of the formatting.
            $nowStr = $now->format("Y-m-d"); //Necessary for comparison, if $start->format("Y-m-d") is put in the comparison clause PHP will still compare the datetime object being formatted, not the output of the formatting.

            if ($startStr < $nowStr) {
                $stop = new \DateTimeImmutable($start->format("Y-m-d")."23:59:59", new \DateTimeZone("UTC"));
                $r->setStop($stop);
                $em->flush();
                
                $txt = $unit->getName() . " had an entry in position (" . $r->getPosition()->getName() . ") spanning datebreak (UTC). Automatically closed at " . $stop->format("Y-m-d H:i:s") . "z.";
                $messages .= "<p>" . $txt . "</p>";

                //Open new entry
                $newStartTime = $stop->modify('+1 second');

                $entry = new Entry();
                $entry->setStart( $newStartTime );
                $entry->setOperator( $r->getOperator() );
                $entry->setPosition( $r->getPosition() );
                $entry->setStudent( $r->getStudent() );
                $em->persist($entry);

                //Assert that there are no future entries before autoopening a new entry
                $futureE = $this->checkFutureEntries($r->getPosition(),true);
                $openE = $this->checkOpenEntries($r->getPosition(), true);

                if ($futureE !== 0 || $openE !== 0) {
                    $txt = "Tried to open a new entry for " . $r->getOperator()->getSignature() . " in the same position (" . $r->getPosition()->getName() . ") next day but there are conflicting entries.";
                    $messages .= "<p>" . $txt . "</p>";
                } else {
                    $em->flush(); //store to DB
                    $txt = "A new entry was opened for " . $r->getOperator()->getSignature() . " in the same position (" . $r->getPosition()->getName() . ")";
                    $messages .= "<p>" . $txt . "</p>";
                }

            }
        }

    }

    return $messages;
}

我什至在这里使用 checkOpenEntries() 运行额外的检查，以查看此时该位置是否存在任何 stoptime == NULL 的条目。最初，我认为这是多余的，因为我认为如果一个请求正在数据库上运行和操作，则另一个请求只有在第一个请求完成后才会启动。

private function checkOpenEntries($position,$checkRelatives = false) {

    $positionsToCheck = array();
    if ($checkRelatives == true) {
        $positionsToCheck = $position->getRelatedPositions();
        $positionsToCheck[] = $position;
    } else {
        $positionsToCheck = array($position);
    }

    //Get all open entries for position
    $repository = $this->em->getRepository('App\Entity\Poslog\Entry');
    $query = $repository->createQueryBuilder('e')
    ->where('e.stop is NULL and e.position IN (:positions)')
    ->setParameter('positions', $positionsToCheck)
        ->getQuery();
    $results = $query->getResult();     

    if(!isset($results[0])) {
        return 0; //tells caller that there are no open entries
    } else {
        if (count($results) === 1) {
            return $results[0]; //if exactly one open entry, return that object to caller
        } else {
            $body = 'Found more than 1 open log entry for position ' . $position->getName() . ' in ' . $position->getACRGroup()->getName() . ' this should not be possible, there appears to be corrupt data in the database.';
            $this->email($body);
                
            $output['success'] = false;
            $output['message'] = $body . ' An automatic email has been sent to ' . $this->globalParameters->get('poslog-email-to') . ' to notify of the problem, manual inspection is required.';
            $output['logdata'] = null;
            return $this->prepareResponse($output);
        }
    }
}

我是否需要使用某种“锁定数据库”方法来启动此功能才能实现我想要做的事情？

我已经测试了所有功能，并且当我模拟各种状态时（即使不应该如此，也为停止时间输入 NULL 等），一切都正常。大多数情况下，一切都运行良好，但在月中的某一天，这种事情发生了......