Simon Wadsworth

Master of Science | Computer Scientist

Limiting bandwidth on Apache
Published Wed 22 June 2011 by Simon Wadsworth in Internet

Now I don’t actually need to enforce data limits on my Apache virtual hosts, because I only host myself, so what I use is irrelevant, but I thought it would be interesting to find out how to do it. I know there are modules out there, but the one I found which I like is mod_cband. It works really well, and enables you to enforce data limits, but also speed limits and number of connections if you are experiencing heavy load say and wish to throttle it a bit. These instructions are based on Ubuntu Server 10.04LTS.

So to start I downloaded the mod_cband source code, available here. After extracting it you then need to compile it. To compile it you need to have APXS2 installed, which I installed by using the following command

sudo apt-get install apache2-prefork-dev

I assume if you are using the threaded version you would need to install the apache2-threaded-dev package. Now after you have installed this package, you can execute ./configure to begin the first phase. This will check dependencies etc and tell you if you are missing anything. You shouldn’t do, but if you are, resolve them before you continue.

Next you need to actually compile the source code. I had a problem here with the Makefile. You need to alter the Makefile slightly. You need to change the line that reads

APXS_OPTS=-Wc,-Wall -Wc,-DDST_CLASS=3

and add in -lm so that it now reads

APXS_OPTS=-lm -Wc,-Wall -Wc,-DDST_CLASS=3

If you don’t you will get an error when you try to start Apache.

Now execute make and when that is completed execute sudo make install. You will get some warnings here regarding comparison of different types, but they shouldn’t effect the running of the module. This will compile the library and install it into the correct location. Now to check that it is enabled type sudo a2enmod cband (assuming of course you are using a2enmod, otherwise you will have to manually edit the configuration files to check that it is there.

Now restart Apache and it should load everything correctly. Now it is time to configure Apache virtual hosts to limit bandwidth. There are many configuration options here, so I will only explain how to enforce Data limits. For other options refer to the mod_cband documentation.

To enable mod_cband your virtual hosts MUST have a ServerName directive, and all cband directives must come after this. If you don’t Apache will throw all sorts of warnings when you try and start it. So the simplest and quickest way to enable a data limit on a virtual host is by placing the following directive in the configuration.

CBandLimit 10M

That will place a limit of 10Megabytes on the user, which is pretty small, and I am sure no one would actually give something that small, but it is very simple to setup. There are many other options you can configure, like a page to send when the bandwidth is used up, or what HTTP code to send, and many more. You can also configure a page that allows you to see the status of the virtual hosts and their various restrictions.


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