|
Directory : /var/www/vhosts/lautnusantara.com/httpdocs/mis/system/Throttle/ |
<?php
/**
* This file is part of CodeIgniter 4 framework.
*
* (c) CodeIgniter Foundation <admin@codeigniter.com>
*
* For the full copyright and license information, please view
* the LICENSE file that was distributed with this source code.
*/
namespace CodeIgniter\Throttle;
use CodeIgniter\Cache\CacheInterface;
/**
* Class Throttler
*
* Uses an implementation of the Token Bucket algorithm to implement a
* "rolling window" type of throttling that can be used for rate limiting
* an API or any other request.
*
* Each "token" in the "bucket" is equivalent to a single request
* for the purposes of this implementation.
*
* @see https://en.wikipedia.org/wiki/Token_bucket
*/
class Throttler implements ThrottlerInterface
{
/**
* Container for throttle counters.
*
* @var CacheInterface
*/
protected $cache;
/**
* The number of seconds until the next token is available.
*
* @var int
*/
protected $tokenTime = 0;
/**
* The prefix applied to all keys to
* minimize potential conflicts.
*
* @var string
*/
protected $prefix = 'throttler_';
/**
* Timestamp to use (during testing)
*
* @var int
*/
protected $testTime;
/**
* Constructor.
*/
public function __construct(CacheInterface $cache)
{
$this->cache = $cache;
}
/**
* Returns the number of seconds until the next available token will
* be released for usage.
*/
public function getTokenTime(): int
{
return $this->tokenTime;
}
/**
* Restricts the number of requests made by a single IP address within
* a set number of seconds.
*
* Example:
*
* if (! $throttler->check($request->ipAddress(), 60, MINUTE)) {
* die('You submitted over 60 requests within a minute.');
* }
*
* @param string $key The name to use as the "bucket" name.
* @param int $capacity The number of requests the "bucket" can hold
* @param int $seconds The time it takes the "bucket" to completely refill
* @param int $cost The number of tokens this action uses.
*
* @internal param int $maxRequests
*/
public function check(string $key, int $capacity, int $seconds, int $cost = 1): bool
{
$tokenName = $this->prefix . $key;
// Number of tokens to add back per second
$rate = $capacity / $seconds;
// Number of seconds to get one token
$refresh = 1 / $rate;
// Check to see if the bucket has even been created yet.
if (($tokens = $this->cache->get($tokenName)) === null) {
// If it hasn't been created, then we'll set it to the maximum
// capacity - 1, and save it to the cache.
$tokens = $capacity - $cost;
$this->cache->save($tokenName, $tokens, $seconds);
$this->cache->save($tokenName . 'Time', $this->time(), $seconds);
$this->tokenTime = 0;
return true;
}
// If $tokens > 0, then we need to replenish the bucket
// based on how long it's been since the last update.
$throttleTime = $this->cache->get($tokenName . 'Time');
$elapsed = $this->time() - $throttleTime;
// Add tokens based up on number per second that
// should be refilled, then checked against capacity
// to be sure the bucket didn't overflow.
$tokens += $rate * $elapsed;
$tokens = $tokens > $capacity ? $capacity : $tokens;
// If $tokens >= 1, then we are safe to perform the action, but
// we need to decrement the number of available tokens.
if ($tokens >= 1) {
$tokens = $tokens - $cost;
$this->cache->save($tokenName, $tokens, $seconds);
$this->cache->save($tokenName . 'Time', $this->time(), $seconds);
$this->tokenTime = 0;
return true;
}
// How many seconds till a new token is available.
// We must have a minimum wait of 1 second for a new token.
// Primarily stored to allow devs to report back to users.
$newTokenAvailable = (int) ($refresh - $elapsed - $refresh * $tokens);
$this->tokenTime = max(1, $newTokenAvailable);
return false;
}
/**
* @param string $key The name of the bucket
*/
public function remove(string $key): self
{
$tokenName = $this->prefix . $key;
$this->cache->delete($tokenName);
$this->cache->delete($tokenName . 'Time');
return $this;
}
/**
* Used during testing to set the current timestamp to use.
*
* @return $this
*/
public function setTestTime(int $time)
{
$this->testTime = $time;
return $this;
}
/**
* Return the test time, defaulting to current.
*
* @TODO should be private
*/
public function time(): int
{
return $this->testTime ?? time();
}
}