Introducing SwitchTower: Distributed deployment for Rails

SwitchTower is a utility for executing commands in parallel on multiple machines. It lets you (among many other things) deploy distributed applications with a single command.

When your application is young you may be deploying it to a single machine, which runs the web server, app server, and database all together. In this situation, deploying manually is not unbearably painful. But as your application grows you may find yourself needing to deploy your application to two web servers, four app servers, and two database servers, atomically. This is where SwitchTower steps in as a pain-killer.

Getting Started

Suppose you have an existing Rails application that you want to deploy to a cluster of machines. SwitchTower attempts to make the entire process as painless as possible:

  • Install SwitchTower. This is as simple as gem install switchtower.
  • Decorate your application with the necessary SwitchTower files. Just do switchtower --apply-to /path/to/your/app.
  • Tell SwitchTower where your application code sits and what machines it should deploy to. Just edit config/deploy.rb and fill in the blanks.
  • Set up your machines so they are ready to receive your application. It’s as easy as rake remote_exec ACTION=setup.
  • Lastly, deploy your application! Just type rake deploy and let the good times roll.

Other Capabilities

In addition to simply moving your application to the various boxes, SwitchTower attempts to make the task of maintaining your deployment simpler. Suppose something goes wrong while checking out your code—SwitchTower will detect that and roll back the change, on all deployed machines. This means it is much harder to wind up with your application out of sync on the various boxes.

Other things SwitchTower can do, out of the box:

  • Database migrations on your production database
  • Enable/disable the web interface (only works with Apache currently)
  • Restart your application on the application servers

SwitchTower also makes it very simple to override and extend the standard tasks, and to write your own. The tasks use a simple language similar to Rake that allows you to automate many different tasks.

More Information

Want to know more about SwitchTower? There’s an entire user manual full of useful tidbits at

Rails 1.0: The Release Candidate (2)

The release of 1.0 is near upon us! It has been a long time in the making, involved a heroic final sprint at RubyConf by the core team, and is a testament to how it’s all been coming together over the last months. Almost three hundred bug fixes, enhancements, and new features have been introduced since 0.13.1 saw the light of day three months ago. That’s on average three per day. So it’s not been a while because of slacking off.

But with all these changes, we want to allow for an extended release-candidate phase before we declare 1.0 a reality. So from today you can get the 1.0 RC 2, which is packaged as version 0.14.1 in the gems.

Over the next two weeks or so, we’re very interested in hearing about bugs and we’ll likely push out a few more release candidates as more and more fixes go in. That said, we can’t fix it all and we surely can’t process all the pending feature enhancements for 1.0. So don’t expect to see an empty Pending Patches or Faults lists. Our main objective is to stamp out the “heinous” bugs: those that significantly affect the many or those that dangerously affect the few.

(The main gem server is pretty over-worked, you may want to do gem install rails --source --include-dependencies to offload it a bit)

Instant Rails: Ruby, Rails, Apache, and MySQL package for Windows

Curt Hibbs has released Instant Rails for Windows. It’s a package of everything needed to get Ruby on Rails running on Apache and MySQL. It’s nicely done as just a single directory, so it doesn’t spread itself all over the system. It’s perfect for trying out Rails in no time at all.

If you’re on OS X, you should look into Locomotive. It’s a similar system for macheads.

Bruce Perens develops model security for Active Record

Bruce Perens is working on model security for Active Record sponsored by Sourcelabs:

I’ve developed ModelSecurity, a new Ruby on Rails facility that helps
developers implement a security defense in depth by implementing
access control within the data model.

If you are like most developers, you think about security when you
program controllers and views. But a bug in your controller or view can
compromise the security of your application, unless your data model has
also been secured.

The economical, flexible, and extremely readable means of specifying
access controls provided by ModelSecurity makes it easier for the
developer to think about security, and makes security assumptions that
might otherwise live in one developers head concrete and communicable
to others.

Please check it out and give Bruce a hand with testing.

Major healthcare application switches from J2EE to Rails

Rick Bradley shares a great case study on how his team replaced a partial J2EE solution that wasn’t moving the team forward fast enough with Rails. Result? A 20:1 reduction in the amount of code needed to solve the problem.

And this is not Yet Another Blog, or even those luxury todo lists we do at 37signals, but a healthcare application that has to play in the regulated world of HIPAA, Sarbanes-Oxley, drug trial requirements, and all that other heavy-duty joy.

Rails takes another step deeper into The Enterprise.