laravel 计划任务的实现原理

laravel的计划任务确实好用，之前就计划吧这个功能研究下，自己造一个给tp5使用

但是研究之后发现，容器这个概念吧代码变得比较抽象，代码读起来的难度比较高

然后研究之后发现除了phpstorm可以追踪大部分代码之外，其他的ide代码追踪功能真的很一般，比如我一般使用NetBeans

看官网在开发9.0不知道啥时候了，等等吧

2018年7月30日11:01:42

补充：laravel主要使用的是容器来实现功能的注册，绑定，使用的 ，但是我逐渐发现laravel的慢的原因估计也是因为这个，虽然容器实现了对象池，但是大多数的调用还是new，理论上都是在对象池只有一个，但是new的东西太多

使用起来更容易了，但是代码可读性也越差了，很多IDE都没办法追踪源代码了

现在对于容器的好与坏，确实有待商榷，现在tp也开始学习这套东西，不知是好是坏

laravel的实现原理就是利用 crontab 每分钟执行一次

计算任务的所需要执行的时间，加上互斥保证只执行一次，防止其他用户执行， 判断是否已经执行过

* * * * * php /path/to/artisan schedule:run >> /dev/null 2>&1

这个就是官方提供的执行计划任务的crontab脚本

提供部分代码参考

public function command($command, array $parameters = [])
    {
        if (class_exists($command)) {
            $command = Container::getInstance()->make($command)->getName();
        }

        return $this->exec(
            Application::formatCommandString($command), $parameters
        );
    }

执行普通命令  php artisan xxxTask

php artisan schedule:run

class CronExpression
{
    const MINUTE = 0;
    const HOUR = 1;
    const DAY = 2;
    const MONTH = 3;
    const WEEKDAY = 4;
    const YEAR = 5;

    /**
     * @var array CRON expression parts
     */
    private $cronParts;

    /**
     * @var FieldFactory CRON field factory
     */
    private $fieldFactory;

    /**
     * @var int Max iteration count when searching for next run date
     */
    private $maxIterationCount = 1000;

    /**
     * @var array Order in which to test of cron parts
     */
    private static $order = array(self::YEAR, self::MONTH, self::DAY, self::WEEKDAY, self::HOUR, self::MINUTE);

    /**
     * Factory method to create a new CronExpression.
     *
     * @param string $expression The CRON expression to create.  There are
     *                           several special predefined values which can be used to substitute the
     *                           CRON expression:
     *
     *      `@yearly`, `@annually` - Run once a year, midnight, Jan. 1 - 0 0 1 1 *
     *      `@monthly` - Run once a month, midnight, first of month - 0 0 1 * *
     *      `@weekly` - Run once a week, midnight on Sun - 0 0 * * 0
     *      `@daily` - Run once a day, midnight - 0 0 * * *
     *      `@hourly` - Run once an hour, first minute - 0 * * * *
     * @param FieldFactory $fieldFactory Field factory to use
     *
     * @return CronExpression
     */
    public static function factory($expression, FieldFactory $fieldFactory = null)
    {
        $mappings = array(
            '@yearly' => '0 0 1 1 *',
            '@annually' => '0 0 1 1 *',
            '@monthly' => '0 0 1 * *',
            '@weekly' => '0 0 * * 0',
            '@daily' => '0 0 * * *',
            '@hourly' => '0 * * * *'
        );

        if (isset($mappings[$expression])) {
            $expression = $mappings[$expression];
        }

        return new static($expression, $fieldFactory ?: new FieldFactory());
    }

/**
     * Get the next or previous run date of the expression relative to a date
     *
     * @param string|\DateTime $currentTime      Relative calculation date
     * @param int              $nth              Number of matches to skip before returning
     * @param bool             $invert           Set to TRUE to go backwards in time
     * @param bool             $allowCurrentDate Set to TRUE to return the
     *                                           current date if it matches the cron expression
     *
     * @return \DateTime
     * @throws \RuntimeException on too many iterations
     */
    protected function getRunDate($currentTime = null, $nth = 0, $invert = false, $allowCurrentDate = false)
    {
        if ($currentTime instanceof DateTime) {
            $currentDate = clone $currentTime;
        } elseif ($currentTime instanceof DateTimeImmutable) {
            $currentDate = DateTime::createFromFormat('U', $currentTime->format('U'));
            $currentDate->setTimezone($currentTime->getTimezone());
        } else {
            $currentDate = new DateTime($currentTime ?: 'now');
            $currentDate->setTimezone(new DateTimeZone(date_default_timezone_get()));
        }

        $currentDate->setTime($currentDate->format('H'), $currentDate->format('i'), 0);
        $nextRun = clone $currentDate;
        $nth = (int) $nth;

        // We don't have to satisfy * or null fields
        $parts = array();
        $fields = array();
        foreach (self::$order as $position) {
            $part = $this->getExpression($position);
            if (null === $part || '*' === $part) {
                continue;
            }
            $parts[$position] = $part;
            $fields[$position] = $this->fieldFactory->getField($position);
        }

        // Set a hard limit to bail on an impossible date
        for ($i = 0; $i < $this->maxIterationCount; $i++) {

            foreach ($parts as $position => $part) {
                $satisfied = false;
                // Get the field object used to validate this part
                $field = $fields[$position];
                // Check if this is singular or a list
                if (strpos($part, ',') === false) {
                    $satisfied = $field->isSatisfiedBy($nextRun, $part);
                } else {
                    foreach (array_map('trim', explode(',', $part)) as $listPart) {
                        if ($field->isSatisfiedBy($nextRun, $listPart)) {
                            $satisfied = true;
                            break;
                        }
                    }
                }

                // If the field is not satisfied, then start over
                if (!$satisfied) {
                    $field->increment($nextRun, $invert, $part);
                    continue 2;
                }
            }

            // Skip this match if needed
            if ((!$allowCurrentDate && $nextRun == $currentDate) || --$nth > -1) {
                $this->fieldFactory->getField(0)->increment($nextRun, $invert, isset($parts[0]) ? $parts[0] : null);
                continue;
            }

            return $nextRun;
        }

        // @codeCoverageIgnoreStart
        throw new RuntimeException('Impossible CRON expression');
        // @codeCoverageIgnoreEnd
    }

判断需要执行的任务是否是当前任务

namespace Illuminate\Console\Scheduling;

use Illuminate\Contracts\Cache\Repository as Cache;

class CacheMutex implements Mutex
{
    /**
     * The cache repository implementation.
     *
     * @var \Illuminate\Contracts\Cache\Repository
     */
    public $cache;

    /**
     * Create a new overlapping strategy.
     *
     * @param  \Illuminate\Contracts\Cache\Repository  $cache
     * @return void
     */
    public function __construct(Cache $cache)
    {
        $this->cache = $cache;
    }

    /**
     * Attempt to obtain a mutex for the given event.
     *
     * @param  \Illuminate\Console\Scheduling\Event  $event
     * @return bool
     */
    public function create(Event $event)
    {
        return $this->cache->add(
            $event->mutexName(), true, $event->expiresAt
        );
    }

    /**
     * Determine if a mutex exists for the given event.
     *
     * @param  \Illuminate\Console\Scheduling\Event  $event
     * @return bool
     */
    public function exists(Event $event)
    {
        return $this->cache->has($event->mutexName());
    }

    /**
     * Clear the mutex for the given event.
     *
     * @param  \Illuminate\Console\Scheduling\Event  $event
     * @return void
     */
    public function forget(Event $event)
    {
        $this->cache->forget($event->mutexName());
    }
}

互斥 的实现

protected function expressionPasses()
    {
        $date = Carbon::now();

        if ($this->timezone) {
            $date->setTimezone($this->timezone);
        }

        return CronExpression::factory($this->expression)->isDue($date->toDateTimeString());
    }

是否过期

自己实现一个计划任务

https://www.cnblogs.com/zx-admin/p/15641124.html