Remote monitoring *VoCore* CPU use

So I really wrote my CPU monitoring webserver program to be able to monitor my Raspberry Pi, but hoped that the code should run on other Linux machines too. Indeed, I have also been testing it in a virtual box running Debian. The code is runnable from Xcode on my Mac, but unfortunately it's a simulation only for testing purposes, because /proc/stat does not exist on Mac OS. So, for the moment, it definitely won't work on the Mac.

But I did think that it would work on OpenWrt, so decided to try it on my VoCore. In anticipation I had already put the necessary stuff in the makefile, so all I needed to do was go to a box with OpenWrt cross compilation set up and do this:  make vocore.

Then I copied the resulting binary executable to my VoCore and it worked straight away. I even made a recording of the initial run for posterity:

Since all the resources (html and javascript files) are embedded in the executable it is really very simple to do, just copy and run a single file. The version compiled for the VoCore came out at 112 Kb in size. Hopefully that's not too bad. I could compress the resource files if space was really important, but I haven't felt the need to do that.

It's pretty good to see this running on a machine about the size of a postage stamp. Obviously I could make it just show a single graph when it runs on a single core machine. Perhaps I'll do that when I get some time.

Remote monitoring Raspberry Pi 2 CPUs

I wanted to visualise of all those CPU cores on my new Raspberry Pi 2, so I decided to build a remote CPU monitoring webserver. The idea is to serve a webpage showing the percentage use of the CPU cores in a nice scrolling graph. Another idea I wanted to try was to keep all the HTML and JavaScript files embedded in the executable. So you only need the single binary program file. It means you just run the program without having to worry about putting supporting files in a particular place.

I'm hopeful that because it's lightweight and written in C the program itself won't consume many of the Raspberry Pi's resources. If you wanted, you could probably run the program as a service when the machine starts and not notice any difference. The CPU data is sent from a minimal Web API, which is built into the webserver. It sends out the CPU percentages as an array in JSON format. This means that most of the work is done by the browser (all the plotting and scrolling) and on the server side we just need to send an array of numbers every second or so. And whilst I was at it, I also included the ability to monitor the core temperature (if it is running on a Raspberry Pi).

I have put the resulting project on GitHub, so if anybody wants to have the ability to monitor their CPU cores over their network they can try it. I expect it will work on other Linux machines too, it's not restricted to the Raspberry Pi. The number of graphs is dynamically updated, depending on the number of cores you have.

This is how it looks (in this case showing the graphs on a simulated iPhone 4s):

If you want to, you can try it out like this:

git clone
cd rCPU/rCPU
sudo ./rcpu 80

...which will only work if you're not running an existing webserver on the machine, otherwise substitute the 80 on the last line for a different port. When the server is running, simply point a browser at your machines IP address (and port if its different than 80) and enjoy.

I did notice that the graphs don't plot very nicely on the default browser included with Raspbian (although if you install an alternative like Chromium it should be OK). But since the purpose is to monitor the CPUs remotely this should not really be an issue.