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Anything pertaining to computers: hardware, software (summary)

Google is not only not evil, it is also human

2009-02-02 by ColasNahaboo in Koala, Tech - 0 Comments
As most of you must know by now, Google suffered an outage on Jan 31, 2009 that was caused by a simple mistake: the search Goliath depended for its results on a small David but didnt properly prepared themselves for the risk of such a dependency on a 3rd-party site. Unbelievably, when the stopbadware site failed to respond (ironically, because a Google bug was DOS-ing them), they decided to... stop serving pages! A saner approach would have been to serve anyways, or perhaps better, reuse a cache of the stopbadware previous results.

Anyways, I was kind of relieved to find that Google was down, because when it happened, I was installing for the first time broadband at my father-in-law house, and not being able to google sent me in a mild panic on trying to understand how a broadband or Vista misconfiguration could result in these strange symptoms! (Well, nothing is impossible with Vista, I know, it can even work sometimes smile

It also brought me memories of a similar blunder I was responsible for at work. I set up a monitoring daemon to check that our vital Intranet Wiki was up. The daemon checked various server health issues, and would eventually restart apache if it could find any other solution. One day, somebody by mistake locked the front page of the wiki so that nobody could see it... and the daemon, unable to see the page, would then endlessly restart apache... The resulting behavior puzzled me quite some time, especially since nobody uses a Wiki front page (everybody dwells in his own little corner) so the main cause was not found immediately... I can see the same human logic here in this bug: we are very bad at expecting the unexpected.

So, whatever you do, take some time to imagine what could go wrong. Expect the unexpected, and even the impossible. I often use an anecdote to bring people to realize this fact: Your computer memory bits can be changed by cosmic rays or radioactivity ! Now ponder this, and try to imagine how you can be sure of your data if it can be changed in your main computer memory, or hard disk controller, or disk... You will not see the world with the same eyes... and you will double check your monthly bank accounts smile

Mercurial web templating

2008-10-09 by ColasNahaboo in Koala, Linux, Tech - 0 Comments
For some time now, I have seen the light and I switched to the new wave of the Distributed Source Control management systems. Linus famous video of his Google talk decided me to try. I was a bit apprehensive at first, wary of engaging myself on a technology that would bring more problems than solutions, but after some days of use, the realisation dawned over me: Distributed Source Control may be one little step for a programmer, but it is a giant step for programming. Why? because, its mental model actually follows your first intuitions that most of us developed as young programmers before using any source control system. Suppose you want to try a feature? instead of just copying the directory, you clone it. You mess an operation? you just remove the directory, no embarrassing traces left to keep the burning scar of shame on you for the following decades of a central repository. You are used to think of your enhancements as patches, you can work with patches. I could go on and on, but many people have done it much better than me so I'll just say that you should definitely try it.

By the way, between the 3 main contenders, git, mercurial (aka HG), and bazaar, I chose mercurial because of its simplicity, its better support of windows (I work in Linux since 1995 but my coworkers currently use Windows), and because some people at ILOG started using git so I wanted to be able to try something else. I did not choose bazaar as I wanted to stay close enough of git, to be able to switch to it if ever my dream to work in a windows-free world materializes one day...

So I started to set up a public web repository of my Open Source personal work with mercurial, which gave me a simple way to publish my work in full detail, but, although mercurial is quite easy to use, but I had a bit of trouble figuring out how to customize its look & feel. So I have made a small cookbook on how to do it that you can find at the page Customizing the style of a HG / mercurial web repository

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Topic revision: r28 - 2009-04-28, ColasNahaboo - This page was cached on 2020-06-17 - 17:18.

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