Get a trace from a 'stack too deep' error in Rails

trace.rb

$enable_tracing = false
#$trace_out = File.open(Rails.root + 'trace.txt', 'w')

set_trace_func proc { |event, file, line, id, binding, classname|
  if $enable_tracing && event == 'call'
    #$trace_out.puts "#{file}:#{line} #{classname}##{id}"
    raise "crash me" if caller_locations.length > 500
  end
}

$enable_tracing = true

This trace.rb can go under config/initializers in a Rails app when you need to track down a recursive loop. Note that it's far too inefficient to have it permanently present!

Credit to the top two answers to this stack overflow question, and indeed the original gist.

Thank you.

Bro, I love you ;-) - that saved my day !

I'm a bit of a noob here. So sorry if my question is simple. I've placed the code under config/initializers.
My rails app fails with "stack level too deep" after I try to open my landing page. How would I run this against my app?

I am getting stack level too deep the moment I run my rails app...right as it tries to go to the landing page.

  Processing by MyController#homepage_index as HTML
Completed 500 Internal Server Error in 12ms

SystemStackError - stack level too deep:
  (gem) activesupport-3.1.0/lib/active_support/notifications/instrumenter.rb:24:in `'

How can I use this code to get the trace?

@badbabykosh it's been a long time since I used this initialiser. It should only be necessary if for some reason you haven't got the backtrace already. Stack overflows are nearly always caused by recursive loops, so you should see repeats of the same method sequence over and over in the backtrace.