Logfile tail the web way

Recently I needed something like web based equivalent of tail -f and tail -n commands, so I could display running tail or last N lines from specific log file. To avoid reinventing the wheel I started looking at previous works on-line and found some interesting bits here and there - one of the most useful being AJAX Logfile Tailer & Viewer, so I based my work on this one.

The trick is, that as far as it does exactly what I needed, this solution requires web server with PHP... and installing web server (not to mention PHP) is not really what I want on my logserver.

Mojolicious to the rescue!

Mojolicious is a very powerful Perl web framework that comes without bloat (almost unheard of these days!) - all you need is standard Perl interpreter and core Perl modules as they come preinstalled with your Linux distro and you can install Mojolicious - no other dependencies. On Debian systems installation is as simple as

apt-get install libmojolicious-perl

and we're up and running. Writing Mojolicious::Lite app is really simple and the best part is that it comes with it's own, built in web server (operating in several different modes if needed). Sounds like nice way to go - no dedicated web server on the machine, self-contained application, etc. One more thing - writing, testing and deploying the whole code to actual machine took less than 10 minutes!

DIY cloud computing - it is easier than you may think!

It seems that the weather forecast for the Internet is a bit "cloudy" nowadays and it will stay this way at least for some time. The "clouds" are a very hot topic right now and more and more companies try to get on the bandwagon as soon as possible - some just run tests while others go into production. You can run "your own" cloud environment for peanuts, the costs are so marginal that it made me laugh when I got my last bill from Amazon AWS, but nevertheless it doesn't always calculate to run your stuff on commercial cloud, especially if you have hardware at hand. The DIY approach is easier than it seems to be. Here is how I've built my own, small "cloud" to solve a problem I was facing at work. It's not a rocket science, it's not full blown management system with hundreds of machines... it works for me and I believe anyone can build similar system - hopefully much better than I did with mine.

Staying away from terminology like HPC/cluster/cloud/grid and meanings of those I use the term "cloud" because I think it's the closest to what I've got now in my prototype - it's still work in progress and it gets even more "cloudy" or change shape otherwise. There won't be any code this time - maybe when I finish it properly and have some proper performance stats - so far it's just a running and usable PoC I describe here :-)

Mass-migrating websites - DNS changes tracking

First shot - migrate several hundreds of websites from one server to another... Copying is a simple task... creating config files is simple task... changing DNS records is boring (and simple)... but keeping track of which DNS domains were properly propagated and which not is a stupid and annoying job... Perl to the rescue!
This is based on several assumptions:

• we use apache2-like way of configuration - all virtual hosts in separate files
• each file has one ServerName statement and possibly ServerAlias with unlimited amount of names following it
• each file has the same name as domain - either with or without 'www' at the beginning (so for sure it has at least one dot in the name)
• we are only interested in the DNS records pointing to the right IP