PHP/Javascript: How I can limit the download speed?

Question

I have the following scenario: You can download from our server some files. If you're a "normal" user, you have a limited bandwidth for example 500kbits. If you're a premium user, you haven't a limit of your bandwidth and can download as fast a possible. But how I can realize this? How does this uploaded & co?

Answer 1

Note: you can do this with PHP, but I would recommend you let the server itself handle throttling . The first part of this answer deals with what your options are if you want to cap the download speed with PHP alone, but below you'll find a couple of links where you'll find how to manage download limits using the server.

There is a PECL extension that makes this a rather trivial task, called pecl_http , which contains the function http_throttle . The docs contain a simple example of how to do this already. This extension also contains a HttpResponse class , which isn't well documented ATM, but I suspect playing around with its setThrottleDelay and setBufferSize methods should produce the desired result (throttle delay => 0.001, buffer size 20 == ~20Kb/sec). From the looks of things, this ought to work:

$download = new HttpResponse();
$download->setFile('yourFile.ext');
$download->setBufferSize(20);
$download->setThrottleDelay(.001);
//set headers using either the corresponding methods:
$download->setContentType('application/octet-stream');
//or the setHeader method
$download->setHeader('Content-Length', filesize('yourFile.ext'));
$download->send();

If you can't/don't want to install that, you can write a simple loop, though:

$file = array(
    'fname' => 'yourFile.ext',
    'size'  => filesize('yourFile.ext')
);
header('Content-Type: application/octet-stream');
header('Content-Description: file transfer');
header(
    sprintf(
        'Content-Disposition: attachment; filename="%s"',
        $file['fname']
    )
);
header('Content-Length: '. $file['size']);
$open = fopen($file['fname'], "rb");
//handle error if (!$fh)
while($chunk = fread($fh, 2048))//read 2Kb
{
    echo $chunk;
    usleep(100);//wait 1/10th of a second
}

Of course, don't buffer the output if you do this :), and it might be best to add a set_time_limit(0); statement, too. If the file is big, it's quite likely your script will get killed mid-way through the download, because it hits the max execution time.

Another (and probably preferable) approach would be to limit the download speed through the server configuration:

• using NGINX
• using Apache2
• using MS IIS (either install the bitrate throttling module, or set the max bandwith)

I've never limited the download rates myself, but looking at the links, I think it's fair to say that nginx is the easiest by far:

location ^~ /downloadable/ {
    limit_rate_after 0m;
    limit_rate 20k;
}

This makes the rate limit kick in immediately, and sets it to 20k. Details can be found on the nginx wiki .

As far as apache is concerned, it's not that much harder, but it'll require you to enable the ratelimit module

LoadModule ratelimit_module modules/mod_ratelimit.so

Then, it's a simple matter of telling apache which files should be throttled:

<IfModule mod_ratelimit.c>
    <Location /downloadable>
        SetOutputFilter RATE_LIMIT
        SetEnv rate-limit 20
    </Location>
</IfModule>

Answer 2

You can use http_throttle from the pecl_http PHP extension:

<?php
// ~ 20 kbyte/s
# http_throttle(1, 20000);
# http_throttle(0.5, 10000);
if (!$premium_user) {
    http_throttle(0.1, 2000);
}
http_send_file('document.pdf');
?>

(The above is based on an example from http://php.net/manual/en/function.http-throttle.php .)

If your server API doesn't allow http_throttle create two distinct, unguessable URLs for your premium and nonpremium users and refer to your HTTP server's documentation for how to throttle one of them. See https://serverfault.com/questions/179646/nginx-throttle-requests-to-prevent-abuse for an example for Nginx. The latter has the benefit of allowing you to sidestep problems like downloads being terminated early due to PHP killing your script.

Answer 3

There's this PHP user land library bandwidth-throttle/bandwidth-throttle

use bandwidthThrottle\BandwidthThrottle;

$in  = fopen(__DIR__ . "/resources/video.mpg", "r");
$out = fopen("php://output", "w");

$throttle = new BandwidthThrottle();
$throttle->setRate(500, BandwidthThrottle::KIBIBYTES); // Set limit to 500KiB/s
$throttle->throttle($out);

stream_copy_to_stream($in, $out);