Memory leak profiling with Rails

# author: scott@sigkill.org
# http://scottstuff.net/blog/articles/2006/08/17/memory-leak-profiling-with-rails
class MemoryProfiler
  
  DEFAULTS = {:delay => 10, :string_debug => false}
 
 def self.start(opt = {}) 
   opt = DEFAULTS.dup.merge(opt)
  
  Thread.new do
    prev = Hash.new(0)
    curr = Hash.new(0)
    curr_strings = []
    delta = Hash.new(0)
  
    file = File.open('log/memory_profiler.log', 'w')
  
    loop do |i|
        begin
        GC.start
        curr.clear
        curr_strings = [] if opt[:string_debug]
  
        ObjectSpace.each_object do |o|
          curr[o.class] += 1 # Marshal.dump(o).size rescue 1
          if opt[:string_debug] and o.class == String
            curr_strings.push o
          end
        end
  
        if opt[:string_debug]
          File.open("log/memory_profiler_strings#{Time.now.to_i}.log", 'w') do |f|
            curr_strings.sort.each do |s|
              f.puts s
            end
          end
          curr_strings.clear
        end

        delta.clear
        (curr.keys + delta.keys).uniq.each do |k,v|
          delta[k] = curr[k] - prev[k]
        end
  
        file.puts "Top 20"
        delta.sort_by { |k, v| -v.abs }[0..19].sort_by { |k, v| -v}.each do |k, v|
          file.printf "%+5d: %s (%d)\n", v, k.name, curr[k] unless v == 0
        end
        file.flush
  
        delta.clear
        prev.clear
        prev.update curr
        GC.start
      rescue Exception => err
        STDERR.puts "** memory_profiler error: #{err}"
      end
        
      sleep opt[:delay]
    end 
    
  end # end loop
 
 end # end Thread.new

end # end def self.start