About 6 years ago (feels like an eternity in Rails world) working at Scribd I’ve started working on porting our codebase from some old version or Rails to a slightly newer one. That’s when I realized, that there wasn’t a ruby gem to help us manage MySQL connections for our vertically sharded databases (different models on different servers). I’ve started hacking on some code to replace whatever we were using back then, finished the first version of the migration branch and then decided to open the code for other people to use. That’s how the DbCharmer ruby gem was born.

For the next few years a lot of new functionality we needed has been added to the gem, making it more complex and immensely more powerful. I’ve enjoyed working on it, developing those features, contributing to the community. But then I left Scribd, stopped being a user of DbCharmer and the situation drastically changed. For quite some time (years) I would keep …

As a leader of a technical operations team I often have to work on technical operations engineer hiring. This process involves a lot of interviews with candidates and during those interviews along with many challenging practical questions I really love to ask questions like “What are the most important resources you think an Operations Engineer should follow?”, “What books in your opinion are must-read for a techops engineer?” or “Who are your personal heroes in IT community?”. Those questions often give me a lot of information about candidates, their experience, who they are looking up to in the community, what they are interested in, and if they are actively working on improving their professional level.

Recently, one of the candidates asked me to share my lists with him and I thought this information could be valuable to other people so I have decided to share it here on my blog.

Must-Read Books List

First …

Scalexis Inc, web performance/scalability consulting firm in Toronto, is looking for a full-time consultant. Being a consulting company on the high-demand market of web application scalability consulting and high-performance web applications development, we need an employee that could perform both web application development and web application performance consulting work.

The main duty of the employee would be to work directly with the customers’ operations teams to detect, analyze and fix performance problems and plan application scalability in accordance with customers’ needs/requests.

The employee would work in a small team of highly professional consultants helping the company to handle growing demand for web applications performance consulting services.

Position is in Toronto. Telecommuting is not possible.

Being a consulting-related position, it …

This week, after 3 months in the works, we’ve finally released version 1.7.0 of DbCharmer ruby gem – Rails plugin that significantly extends ActiveRecord’s ability to work with multiple databases and/or database servers by adding features like multiple databases support, master/slave topologies support, sharding, etc.

New features in this release:

• Rails 3.0 support. We’ve worked really hard to bring all the features we supported in Rails 2.X to the new version of Rails and now I’m proud that we’ve implemented them all and the implementation looks much cleaner and more universal (all kinds of relations in rails 3 work in exactly the same way and we do not need to implement connection switching for all kinds of weird corner-cases in ActiveRecord).
• Forced Slave Reads functionality. Now …

Having a reverse-proxy web cache as one of the major infrastructure elements brings many benefits for large web applications: it reduces your application servers load, reduces average response times on your site, etc. But there is one problem every developer experiences when works with such a cache – cached content invalidation.

It is a complex problem that usually consists of two smaller ones: individual cache elements invalidation (you need to keep an eye on your data changes and invalidate cached pages when related data changes) and full cache purges (sometimes your site layout or page templates change and you need to purge all the cached pages to make sure users will get new visual elements of layout changes). In this post I’d like to look at a few techniques we use at …

Back in November 2009 I was working on a project to port Scribd.com code base to Rails 2.2 and noticed that some old plugins we were using in 2.1 were abandoned by their authors. Some of them were just removed from the code base, but one needed a replacement – that was an old plugin called acts_as_readonlyable that helped us to distribute our queries among a cluster of MySQL slaves. There were some alternatives but we didn’t like them for one or another reasons so we’ve decided to go with creating our own ActiveRecord plugin, that would help us scale our databases out. That’s the story behind the first release of DbCharmer.

Today, six months after the first release of …

Today I’m proud to announce the first public release of our ActiveRecord database connection magic plugin: DbCharmer.

DB Charmer – ActiveRecord Connection Magic Plugin

DbCharmer is a simple yet powerful plugin for ActiveRecord that does a few things:

1. Allows you to easily manage AR models’ connections (switch_connection_to method)
2. Allows you to switch AR models’ default connections to a separate servers/databases
3. Allows you to easily choose where your query should go (on_* methods family)
4. Allows you to automatically send read queries to your slaves while masters would handle all the updates.
5. Adds multiple databases migrations to ActiveRecord

Installation

There are two options when …

It’s been a while since I’ve posted my first post about the way we do document pages caching in Scribd and this approach has definitely proven to be really effective since then. In the second post of this series I’d like to explain how we handle our complex document URLs and logged in users in the caching architecture.

First of all, let’s take a look at a typical Scribd’s document URL: http://www.scribd.com/doc/1/Improved-Statistical-Test.

As we can see, it consists of a document-specific part (/doc/1) and a non-unique human-readable slug part (/Improved-Statistical-Test). When a user comes to the site with a wrong slug in the document URL, we need to make sure we send the user to the correct …

Long time ago, in 2002 I decided to create my own point of presence in the Internet. Back then I’ve got pretty nice domain (scoundrel.kremenchug.net), hacked up a few pages on php, added a guestbook and that was it. Many years it was almost static and I did a few updates on my resume page few times a year. Later I’ve switched the site to wordpress to make it easier to manage my resume and stuff…

And 3 years ago in March 2006 I’ve decided to start my own blog. I took a standard template and started the blog on a separate domain while the domain was on its own domain name… This spring my …

loops is a small and lightweight framework for Ruby on Rails and Merb created to support simple background loops in your application which are usually used to do some background data processing on your servers (queue workers, batch tasks processors, etc).

Originally loops plugin was created to make our (Scribd.com) own loops code more organized. We used to have tens of different modules with methods that were called with script/runner and then used with nohup and other not so convenient backgrounding techniques. When you have such a number of loops/workers to run in background it becomes a nightmare to manage them on a regular basis (restarts, code upgrades, status/health checking, etc).

After a short time of writing our loops in more …