Can anyone recommend best practices for profiling Ruby on Rails software under Passenger/nginx combination in a live server environment?

Question

I am attempting to determine what can possibly be the causative factor for 20+ second response times from a Rails 3 application located in EC2 using Elasticache. I have reason to believe the problem is in fact cache related, but I have no numbers to prove it. I'd like to get those numbers. For the sake of completeness, we're running the applications atop Ubuntu 12.04 .

Searching Google, I found nothing directly relevant to my situation, and no StackOverflow topics I could find were even remotely relevant to my situation. If anyone can point me to some documentation on the matter, I'd be quite appreciative. Thank you!

Answer 1

I've found the best tool for this to be New Relic.

http://newrelic.com/

I don't work for them and get no benefit from you trying them.

They have a free level that you can start with. If you go up to the non-free version you can literally trace all your requests through different models and into the database telling you how long the app spent in each section. It's a great tool for profiling.

Answer 2

Do you, by any chance have access to standard web logs including URLs and response times?

I faced a similar situation, searched the web, found nothing relevant, and eventually decided to roll my own, which I shared in this SO post:

Profiling a multi-tiered, distributed, web application (server side)

While it is far from perfect and may be too high level for some use-cases, it gave me a pretty quick and broad insight into where the application I was trying to profile is spending most of its time in, and what the slowest parts are. HTH.

The best parts of it are that:

• It is 100% platform and programming language independent.
• It is a 100% free software solution