The MySQL installation packages for Mac OS X (on mysql.com) prevent you from downgrading MySQL. They keep track of which versions have been previously installed, and then make the brain dead assumption that you will only ever need to upgrade. It's farcical; even if you remove all copies of MySQL the installer still prevents you from installing an earlier version, unless you know where the silly buggers squirrelled away their nuts.

Read on if you want to poke MySQL with a pointy stick...

A user recently reported poor performance on one of our Rails apps. I pulled up New Relic's performance graphs and checked what was happening around the time that we received the email. Sure enough there was a massive spike over a 10 minute period in the time taken to serve a request.

Analyse Rails log files with cut, sort and uniq

Nokogiri complains that the version of libxml2 installed on Mac OS X Leopard is over 4 years out of date. Well we can't have that now can we!

Update your libxml2 library

You can connect to a PostgreSQL database from Ruby using the pg gem, but if the pg_config program isn't in your path you'll run into problems during installation.

This article is mainly here to provide some Google juice for those who hit the same problem...

Compiling the pg gem

This isn't particularly difficult, but if you're not familiar with Postgres on Ubuntu it could take you ten minutes to work it out:

$ sudo apt-get install postgresql-8.2 postgresql-server-dev-8.2 -y
$ sudo apt-get install libsqlite3-dev -y
$ sudo gem install merb do_postgres

The merb gem depends on the do_sqlite3 DataMapper database driver, so we need the libsqlite3-dev package in order to compile it. You can remove it afterwards if you like.

So you've just written a nice new Sinatra application, and you want to get it running on your web server. How hard can it be? Well with Vlad the Deployer, it's actually rather easy.

Read about how to roll out Sinatra

The images, CSS and JavaScript files served up by your Rails application can usually be cached by the web browser, rather than being downloaded every time the browser loads a page on your site. Rails gives you some help here, but it doesn't happen automatically -- you need to configure your web server to set the HTTP Expires header.

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God is a very neat piece of software, frequently used by Rails developers to monitor mongrel servers, and restart them if/when they crash or use up too many system resources.

Its use isn't limited purely to monitoring web servers though; you can monitor pretty much anything you like. Read on to see how to configure it to monitor the Ruby job processing daemon, BackgrounDRb.

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I used to work for a company that was in the business of deploying laptops running Linux into hospitals. We automated the installation of these laptops to such a degree that all we had to do build a new laptop was unwrap it, plug it into an ethernet network and turn it on. We used PXE boot and our own bespoke deployment system to achieve it. It even supported deploying automatic configuration updates over a mobile phone connection, while the laptops were in a different country.

It never seems to be worth going to the effort to setup a tool like puppet when configuring a new desktop computer, a virtual server to run your blog, or a VPS for a small client who is keen to keep the budget down. But why should automation be expensive?

If you like the idea of an automated server build on the cheap, read on...

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