Your Rails app appears to be humming along just fine. But then, out of the blue, one of your most important customers emails your support team: "the site is loading slowly - is something up"?
You frantically browse around the site, but everything seems fine. You double-check the charts: things look normal. Is the customer trying to trick you? Is monitoring broken?
In this post, I'll show how to slice-and-dice your Rails application log to uncover performance issues on the edges. With your new super powers, you'll be able to find that needle in the haystack.