<?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) $results[0];
}
/**
* Determine if the key has been "accessed" too many times.
*
* @return bool
*/
public function tooManyAttempts()
{
[$this->decaysAt, $this->remaining] = $this->redis->eval(
$this->tooManyAttemptsLuaScript(), 1, $this->name, microtime(true), time(), $this->decay, $this->maxLocks
);
return $this->remaining <= 0;
}
/**
* Clear the limiter.
*
* @return void
*/
public function clear()
{
$this->redis->del($this->name);
}
/**
* 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;
}
/**
* Get the Lua script to determine if the key has been "accessed" too many times.
*
* 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 tooManyAttemptsLuaScript()
{
return <<<'LUA'
if redis.call('EXISTS', KEYS[1]) == 0 then
return {0, ARGV[2] + ARGV[3]}
end
if ARGV[1] >= redis.call('HGET', KEYS[1], 'start') and ARGV[1] <= redis.call('HGET', KEYS[1], 'end') then
return {
redis.call('HGET', KEYS[1], 'end'),
ARGV[4] - redis.call('HGET', KEYS[1], 'count')
}
end
return {0, ARGV[2] + ARGV[3]}
LUA;
}
}