How to Switch Your Cedar Heroku App from Webrick to Thin

Received an en email today from Cody K on my use of Webrick in production for Lean Domain Search:

Hey Matt,

Lean Domain Search is really neat – thanks for making it available.

Just wanted to let you know that it’s a really bad idea to run Ruby web apps with Webrick in production – you should be using something like nginx and either Unicorn or Passenger. Those are battle-hardened and production-ready, whereas Webrick’s sole purpose is for development environments, and, as such, is not heavily tested (if at all) for security issues and whatnot.

Just a friendly heads up. :) Thanks again.

Heroku’s Rails 3 docs are also pretty clear on this and I remember reading it during my initial upgrade, but never got around to actually doing it.

Thin is a recommended app server over Webrick (the default for rails).

Switching to Thin is pretty easy:

1. Add gem 'thin' to your Gemfile:

I added it to the production group because I want to keep using Webrick in development for now.

2. Make sure that you run bundle install to update your Gemfile otherwise you’ll receive a warning like this when you push to Heroku:

You are trying to install in deployment mode after changing
your Gemfile. Run `bundle install` elsewhere and add the
updated Gemfile.lock to version control.
You have added to the Gemfile:
* thin

3. Add a Procfile to your root directory to instruct Heroku to use Thin instead of Webrick:

4. Commit and push your updated app to Heroku.

If all went well, you should see something like this in your logs:

2012-01-18T12:44:33+00:00 app[web.1]: >> Using rack adapter
2012-01-18T12:44:33+00:00 app[web.1]: >> Thin web server (v1.3.1 codename Triple Espresso)
2012-01-18T12:44:33+00:00 app[web.1]: >> Listening on, CTRL+C to stop
2012-01-18T12:44:33+00:00 app[web.1]: >> Maximum connections set to 1024
2012-01-18T12:44:34+00:00 heroku[web.1]: State changed from starting to up

Too easy.

One thing confused me though: How did Cody know that I was using Webrick? I emailed him and asked.

His response:

I mistakenly typed some bogus characters in at the end of my address bar while I was on your site…something like this:^jf

Sure enough, Webrick fails loudly when the URL includes a caret:


2 thoughts on “How to Switch Your Cedar Heroku App from Webrick to Thin

  1. Question I have is – why is Heroku using Webrick by default? It uses Postgres by default (as opposed to Sqlite) why not a production ready web-server?

  2. So I just spent like an hour searching for a way to switch from WeBrick to Thin – (WeBrick complained about the long search URL’s I had.) This is by far the most clear, concise explanation I found. Thanks!

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