Strange behaviour with Apache mod_ratelimit

Question

I'm trying to use mod_ratelimit, but it's exhibiting some odd behaviour.

Initially, my configuration was:

<Virtualhost>
...
<Directory /var/www/public>
    Order               Allow,Deny
    Allow from All

    Options       FollowSymLinks
    AllowOverride All

    SetOutputFilter RATE_LIMIT
    SetEnv rate-limit 250
</Directory>
...
</Virtualhost>

I've also tried:

<Virtualhost>
    ...
    SetOutputFilter RATE_LIMIT
    SetEnv rate-limit 250
    ...
</Virtualhost>

and

<Virtualhost>
<Location>
    ...
    SetOutputFilter RATE_LIMIT
    SetEnv rate-limit 250
    ...
</Location>
</Virtualhost>

I was expecting the 8 MB file I was downloading to take about 30 seconds. It was done in an instant.

I've tried several values for rate-limit and used wget to time them:

rate-limit | download speed
-----------+---------------
       250 | 440 MB/s
       100 | 440 MB/s
        50 | 440 MB/s
        30 |  20 kB/s
        25 |  20 kB/s
        10 |   6 kB/s
         1 | 500  B/s

This is apache 2.4 running on Ubuntu 14.04

Answer 1

This may be a silly question, however, I ask because it has been missed before: Is the module enabled?

You can see this in /etc/apache2/mods-enabled/. By default, this module is not enabled.

From: https://www.server-world.info/en/note?os=Ubuntu_14.04&p=httpd2&f=7

root@www:~# a2enmod ratelimit 
root@www:~# vi /etc/apache2/conf-available/ratelimit.conf
# create new
# for example, limit bandwidth as 500 KB/sec under the /download location
<IfModule mod_ratelimit.c>
    <Location /download>
        SetOutputFilter RATE_LIMIT
        SetEnv rate-limit 500
    </Location>
</IfModule>
root@www:~# a2enconf ratelimit 
root@www:~# /etc/init.d/apache2 restart

Another popular option is mod_dialup found at: http://httpd.apache.org/docs/2.4/mod/mod_dialup.html