Rackspace’s DNS rate limiting

Today, while I was having lunch, I started receiving email notifications about Niume’s servers not responding. In the beginning it was just one server, so I removed it from the load balancer, then restarted the httpd process and put it back again.

But then the other servers started behaving the same way, even though the load was well under capacity. Between those email notifications, there was a Rackspace support email:

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Motion Detection Surveillance System with raspberry pi

One of these days, the disc brake lock of my bike couldn’t unlock. My first thought was that somebody tried to steal the bike. Probably this isn’t the case, but I took some immediate measures to restore my inner peace again.

I used to have a windows laptop running yawcam (Yet Another Webcam Software) and recording images when motion was detected. But this laptop is now dead and I don’t use Windows at all anymore, so I had to find a Linux equivalent.

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Recruitment Ranting

As the Chief Software Engineer of Niume Ltd and as a person who thinks that the Recruitment Industry does not perform well within the Software Industry (apart from gathering CVs), I have to personally interview and test the skills of each applicant.

Because of this, I stumble upon millions of things that annoy me and can be pretty well summarized in this blog post here and this one here, written by a fellow software developer in Greece. Since Greek is not the language the masses are familiar with, I am going to translate most of the points made and maybe add mine too, in order to make applicants more successful next time.

So, let the ranting begin.

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Last Push of the Day/Night

All DevOps out there who use Git as a version control system probably know what it feels like. And it is a very special feeling.
(You also get this feeling with SVN by committing but for me it’s not the same.)

I prefer the push thing. I like the semantics, the poetry about it, its cruelty, everything. And I hate it so much at the same time.

The action of pushing is like signing and assuring that the spaceship can launch tomorrow.

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Thoughts on Parallelization

One of these days, as I was revisiting my early high school memories from notebooks, books, love-letters etc, I stumbled upon this simple but also tricky problem:

“One pump can fill up a tank with petrol in 25 minutes.

 Another tank can fill up the same tank with petrol in 15 minutes.

 If we combine both pumps together, how much time is needed for the tank to be filled?”

You can try solving it on your own, before scrolling to the answer. Don’t spoil it so quickly!

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Connect WEKA to MySQL

I am attending a Data Mining class here in London and hopefully I am quite interested in the field and I like it a lot.

Since I started my own research on the topic too, and I have tons of commercial data in the databases I administer for playing around, I found a very nice, free and open source tool (Can it get any better?) for the job, WEKA.
(Waikato Environment for Knowledge Analysis)

It is developed at the University of Waikato, New Zealand. Weka is free software available under the GNU General Public License.

One of the nice things of the software is that it uses JDBC (Java Database Connectivity), so you can connect to any database that supplies you with a JDBC driver. Also there is a JDBC to ODBC bridge driver, in order to connect to ODBC supported databases. So to sum things up, you can connect to almost every decent database management system.

Anyway, in theory it works really well, but there is a grey zone on how to practically connect to a database when using WEKA.

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University Firewalls and Proxies – FIXED

Yeap, I now have fully functional sensor-free internet and it wasn’t such a complicated procedure in the end.

The only thing I needed was a linux webserver that I could track its IP Address, (using a dynDNS service or a static IP), squid proxy server software running on the webserver, a SSH reliable client (I use PUTTY) if you are running on Windows. If on Linux, you’re in luck, SSH client functionality comes out-of-the-box.

How did I do it? Implemented, not academic? Keep reading.

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University Firewalls and Proxies

I really have a problem with my University Internet Connection. It is very fast and reliable etc…

BUT

I think the whole university intranet firewall isn’t properly configured. Many times, while I am working, I simply cannot access websites that use SSL (the https thing). Not even Google search.

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