Pragmatic Automation

SwitchTower as an Automated Deployment Archetype
29 Nov 05 -
I’ve been remiss to have delayed mentioning SwitchTower until now. It’s an open-source utility that makes one-step deployment to one or more machines both possible and painless.

Say, for example, you need to roll out a new release of your killer app to two web servers, four application servers, and a database server. You could manually log in to each of those machines and type a list of commands, or just let SwitchTower do it for you:

  rake deploy

That single incantation causes SwitchTower to execute the commands listed in your deployment recipe in parallel (and atomically) on multiple machines. (It uses ssh to communicate with the remote machines.) It’s really that easy.

But then you notice that the application you just deployed has a bug. After giving your manager fifty push-ups, you’re thankful you can press the "undo" button:

  rake rollback

That command rolls back the application to the last deployed version on all deployed machines. Yes, it’s really that easy.

I’ve been starting to use SwitchTower on all my Rails projects, and demo’ing it in our Pragmatic Rails Studio. As a result, SwitchTower has truly spoiled me. It’s an automator’s dream, and I can’t imagine going back to manual deployment gyrations.

That brings us to the point of this elevator pitch: Can you deploy and roll back software releases this easily and consistently on your project? If not, I’d recommend you give the SwitchTower manual a read, especially if you aren’t building Rails applications. That’s right, even if you’ve never heard of Ruby or Rails you owe it to yourself to check out SwitchTower because its concepts aren’t specific to Ruby or Rails. And in fact it seems possible to use SwitchTower as the deployment vehicle for apps of any size and color by customizing a core set of tasks. I’d love to hear of efforts to adapt SwitchTower to J2EE projects, for example.

Every software project can benefit from a deployment process that takes less time and money without sacrificing quality. SwitchTower is an archetype of automated deployment. Check it out before rolling your own solution.