Agile Web Operations

Photo by Juan Lupión

As I mentioned in my short comparison of Puppet vs. Capistrano, we're currently using Capistrano not only for deployment and live monitoring of our application, but also for configuration management.

Using How-To Documents For Configuration Management

Before getting started with Capistrano, I used to write very detailed how-to documents to make sure that I didn't need to re-learn any installation or configuration procedures I had already done. In fact, I got bit every time I slacked off and failed to write down what I did. Yes, I regretted every single time I tried to take the seemingly “fast” route, having to google my way through a complex and nasty configuration again. I can't imagine a worse way of wasting your time...

We’re currently using Capistrano not only to deploy our Ruby on Rails application, but also to setup and manage our physical and virtual (Xen based) servers. We have Capistrano recipes for adding users, installing packages like apache or mysql, configuring a Xen VM and more. Coming accross puppet, I started to wonder about the essential difference between the two. Puppet claims to enable the user to automate server management to a large extent, a goal which we already reached by implementing our custom Capistrano recipes. So, what are the differences between the two?

Photo by priittammets

After years spent working with Cfengine, Luke Kanies decided to form the company Reductive Labs in 2005 and Puppet, a long time idea and quickly stabilizing prototype, was born. He describes it as an open-source, next-generation server automation tool. Configuration files (called manifests) are written declaratively, and there is a client/server model for distribution handling. The configuration library, however, is what really distinguishes Puppet from its predecessor.

As promised in my last post about configuration management, I want to introduce you to one of the key Open Source configuration management players on the scene today - Cfengine. Embarked upon in 1993 by Mark Burgess, Cfengine has helped system administrators configuring and maintaining their servers in the data center for over a decade - bringing order to chaos and discipline to exhibitionism. This C based configuration management system can be manually executed, daemon driven and run by crontab and is controlled through a series of text-file configurations. Making use of a mostly declarative language, a single Cfengine statement can potentially cause hundreds of operations to be executed on multiple hosts across the network. Installation nowadays is as painless as yum install cfengine (Fedora Core/SuSE) or apt-get install cfengine2 (Debian).

Photo by vrysxy

The Velocity 2008 Conference hosted many excellent presentations and discussions concerning web performance and operations. Adam Jacob, of HJK Solutions, presented how his company goes about "Building An Automated Infrastructure". To briefly explain what an automated infrastructure is, let's think of servers and data as office buildings and automobiles. Would it make sense to begin construction of these without electricity, running water and roads? This infrastructure ties together our entire lives and greatly improves our standard of living. Correspondingly, basic IT tasks such as operating system installs, version control systems, configuration management and application deployment tie our servers and data together and greatly improve our ability to conduct business with customers.

I'd like to share my views on Configuration Management (CM) and the role it could play in your data center.