How do I debug a slow rails app boot time?

Question

Our rails app is nice and fast once it is loaded but the startup is brutally slow. Console, passenger etc all take almost 10 seconds to kick in. Seems to be way more than it should be.

What tools or methods should I use to hone in on the slowest parts? What are the usual suspects?

Answer 1

I know this is an old question but I recently had an issue with load times and this is my fork of gem which helped me find which gems were the slowest, the good thing about this gem is that loads up with the rails console, and all the initializers are run.

https://github.com/mark-ellul/Bumbler