Laravel-Throttle

思考并回答以下问题：

使用

可以使用时间或并发（Laravel-Funnel）来控制队列任务。该功能特性在队列任务与有频率限制的API交互时很有帮助。

通过throttle方法，你可以限定给定类型任务每60秒只运行10次。如果不能获取锁，需要将任务释放回队列以便可以再次执行：

Redis::throttle('key')->allow(10)->every(60)->then(function () {
    // Job logic...
    // 1分钟点击了100下，但是1分钟只有10条数据写入文件
    // file_put_contents('1.txt', date('Y-m-d H:i:s').PHP_EOL, FILE_APPEND);
}, function () {
    // Could not obtain lock...

    return $this->release(10);
});

注：在上面的例子中，key可以是任意可以唯一标识你想要限定访问频率的任务类型的字符串。举个例子，这个键可以基于任务类名和操作Eloquent模型的ID进行构建。

源码

Illuminate\Redis\Limiters\DurationLimiter.php

<?php

namespace Illuminate\Redis\Limiters;

use Illuminate\Contracts\Redis\LimiterTimeoutException;

class DurationLimiter
{
    /**
     * The Redis factory implementation.
     *
     * @var \Illuminate\Redis\Connections\Connection
     */
    private $redis;

    /**
     * The unique name of the lock.
     *
     * @var string
     */
    private $name;

    /**
     * The allowed number of concurrent tasks.
     *
     * @var int
     */
    private $maxLocks;

    /**
     * The number of seconds a slot should be maintained.
     *
     * @var int
     */
    private $decay;

    /**
     * The timestamp of the end of the current duration.
     *
     * @var int
     */
    public $decaysAt;

    /**
     * The number of remaining slots.
     *
     * @var int
     */
    public $remaining;

    /**
     * Create a new duration limiter instance.
     *
     * @param  \Illuminate\Redis\Connections\Connection  $redis
     * @param  string  $name
     * @param  int  $maxLocks
     * @param  int  $decay
     * @return void
     */
    public function __construct($redis, $name, $maxLocks, $decay)
    {
        $this->name = $name;
        $this->decay = $decay;
        $this->redis = $redis;
        $this->maxLocks = $maxLocks;
    }

    /**
     * Attempt to acquire the lock for the given number of seconds.
     *
     * @param  int  $timeout
     * @param  callable|null  $callback
     * @return mixed
     *
     * @throws \Illuminate\Contracts\Redis\LimiterTimeoutException
     */
    public function block($timeout, $callback = null)
    {
        $starting = time();

        while (! $this->acquire()) {
            if (time() - $timeout >= $starting) {
                throw new LimiterTimeoutException;
            }

            usleep(750 * 1000);
        }

        if (is_callable($callback)) {
            return $callback();
        }

        return true;
    }

    /**
     * Attempt to acquire the lock.
     *
     * @return bool
     */
    public function acquire()
    {
        $results = $this->redis->eval(
            $this->luaScript(), 1, $this->name, microtime(true), time(), $this->decay, $this->maxLocks
        );

        $this->decaysAt = $results[1];

        $this->remaining = max(0, $results[2]);

        return (bool) $results[0];
    }

    /**
     * Get the Lua script for acquiring a lock.
     *
     * KEYS[1] - The limiter name
     * ARGV[1] - Current time in microseconds
     * ARGV[2] - Current time in seconds
     * ARGV[3] - Duration of the bucket
     * ARGV[4] - Allowed number of tasks
     *
     * @return string
     */
    protected function luaScript()
    {
        return <<<'LUA'
local function reset()
    redis.call('HMSET', KEYS[1], 'start', ARGV[2], 'end', ARGV[2] + ARGV[3], 'count', 1)
    return redis.call('EXPIRE', KEYS[1], ARGV[3] * 2)
end

if redis.call('EXISTS', KEYS[1]) == 0 then
    return {reset(), ARGV[2] + ARGV[3], ARGV[4] - 1}
end

if ARGV[1] >= redis.call('HGET', KEYS[1], 'start') and ARGV[1] <= redis.call('HGET', KEYS[1], 'end') then
    return {
        tonumber(redis.call('HINCRBY', KEYS[1], 'count', 1)) <= tonumber(ARGV[4]),
        redis.call('HGET', KEYS[1], 'end'),
        ARGV[4] - redis.call('HGET', KEYS[1], 'count')
    }
end

return {reset(), ARGV[2] + ARGV[3], ARGV[4] - 1}
LUA;
    }
}

Illuminate\Redis\Limiters\DurationLimiterBuilder.php

<?php

namespace Illuminate\Redis\Limiters;

use Illuminate\Contracts\Redis\LimiterTimeoutException;
use Illuminate\Support\InteractsWithTime;

class DurationLimiterBuilder
{
    use InteractsWithTime;

    /**
     * The Redis connection.
     *
     * @var \Illuminate\Redis\Connections\Connection
     */
    public $connection;

    /**
     * The name of the lock.
     *
     * @var string
     */
    public $name;

    /**
     * The maximum number of locks that can obtained per time window.
     *
     * @var int
     */
    public $maxLocks;

    /**
     * The amount of time the lock window is maintained.
     *
     * @var int
     */
    public $decay;

    /**
     * The amount of time to block until a lock is available.
     *
     * @var int
     */
    public $timeout = 3;

    /**
     * Create a new builder instance.
     *
     * @param  \Illuminate\Redis\Connections\Connection  $connection
     * @param  string  $name
     * @return void
     */
    public function __construct($connection, $name)
    {
        $this->name = $name;
        $this->connection = $connection;
    }

    /**
     * Set the maximum number of locks that can obtained per time window.
     *
     * @param  int  $maxLocks
     * @return $this
     */
    public function allow($maxLocks)
    {
        $this->maxLocks = $maxLocks;

        return $this;
    }

    /**
     * Set the amount of time the lock window is maintained.
     *
     * @param  int  $decay
     * @return $this
     */
    public function every($decay)
    {
        $this->decay = $this->secondsUntil($decay);

        return $this;
    }

    /**
     * Set the amount of time to block until a lock is available.
     *
     * @param  int  $timeout
     * @return $this
     */
    public function block($timeout)
    {
        $this->timeout = $timeout;

        return $this;
    }

    /**
     * Execute the given callback if a lock is obtained, otherwise call the failure callback.
     *
     * @param  callable  $callback
     * @param  callable|null  $failure
     * @return mixed
     *
     * @throws \Illuminate\Contracts\Redis\LimiterTimeoutException
     */
    public function then(callable $callback, callable $failure = null)
    {
        try {
            return (new DurationLimiter(
                $this->connection, $this->name, $this->maxLocks, $this->decay
            ))->block($this->timeout, $callback);
        } catch (LimiterTimeoutException $e) {
            if ($failure) {
                return $failure($e);
            }

            throw $e;
        }
    }
}

Illuminate\Redis\Connections\Connection.php

<?php

namespace Illuminate\Redis\Connections;

use Closure;
use Illuminate\Contracts\Events\Dispatcher;
use Illuminate\Redis\Events\CommandExecuted;
use Illuminate\Redis\Limiters\ConcurrencyLimiterBuilder;
use Illuminate\Redis\Limiters\DurationLimiterBuilder;
use Illuminate\Support\Traits\Macroable;

abstract class Connection
{
    use Macroable {
        __call as macroCall;
    }

    /**
     * Throttle a callback for a maximum number of executions over a given duration.
     *
     * @param  string  $name
     * @return \Illuminate\Redis\Limiters\DurationLimiterBuilder
     */
    public function throttle($name)
    {
        return new DurationLimiterBuilder($this, $name);
    }
}