How do you view a sample of the call stack in ruby?

Question

I\'m investigating different optimization techniques, and I came across this post Analyzing Code for Efficiency? by someone who believes that sampling the call stack is more

Answer 1

How about sending signal to the ruby process, and creating a handler for the signal which dumps all stacks?

From http://le-huy.blogspot.com/2012/04/dump-backtrace-of-all-threads-in-ruby.html we have this example :

require 'pp'

def backtrace_for_all_threads(signame)
  File.open("/tmp/ruby_backtrace_#{Process.pid}.txt","a") do |f|
      f.puts "--- got signal #{signame}, dump backtrace for all threads at #{Time.now}"
      if Thread.current.respond_to?(:backtrace)
        Thread.list.each do |t|
          f.puts t.inspect
          PP.pp(t.backtrace.delete_if {|frame| frame =~ /^#{File.expand_path(__FILE__)}/},
               f) # remove frames resulting from calling this method
        end
      else
          PP.pp(caller.delete_if {|frame| frame =~ /^#{File.expand_path(__FILE__)}/},
               f) # remove frames resulting from calling this method
      end
  end
end

Signal.trap(29) do
  backtrace_for_all_threads("INFO")
end

Then we need to send the signal to the appropriate process :

ps afxw | grep ruby
kill -29 <pid>
ls -l /tmp/ruby*
vi /tmp/ruby_backtrace_...

Repeat the signal at appropriate sampling time.

Answer 2

Just put

puts caller

anywhere in the code. If you don't like its format, it's an array of strings, so you can do some regex manipulation for a desired output.

Answer 3

You can throw an exception at any time, and then look at the $@ predefined variable, which returns an array of backtrace data. E.g. put this in foo.rb:

begin                                                                        
  raise 'foo'                                                                
rescue                                                                       
  puts $@                                                                    
end  

Then run it:

$ ruby foo.rb 
foo.rb:2:in `<main>'