profiler.rb

## Profiler
## A wrapper for the rblineprof library to pretty-print the profile data
## and enable customization of the output
## Based heavily on tmm1's examples
## This assumes that rblineprof lib is installed in Rails.root + 'vendor/rblineprof/ext'
## https://github.com/tmm1/rblineprof
class Profiler

  # see docs for self.log_line method
  @@logger = Proc.new { |line| Rails.logger.info line }

  # see docs for self.format_line method
  @@formatter = Proc.new { |file, profile_data, line, num|
    wall, cpu, calls = profile_data

    if calls && calls > 0
      "(((  % 8.1fms + % 8.1fms (% 5d) | %s" % [cpu/1000.0, (wall-cpu)/1000.0, calls, line]
    else
      "(((                                  | %s" % [line]
    end
  }

  # override the default logger for the profiler
  # the block should accept an argument signature that matches Profiler.log_line, below.
  def self.set_logger( &block )
    @@logger = block
  end

  # override the default formatter
  # the block should accept an argument signature that matches Profiler.format_line, below.
  def self.set_formatter( &block )
    @@formatter = block
  end

  # accessor for @@logger
  def self.logger
    @@logger
  end

  # accessor for @@formatter
  def self.formatter
    @@formatter
  end

  # log a line using the @@logger Proc.
  # it should take the same method signature as this method
  def self.log_line(line)
    self.logger.call line
  end

  # format a given line to be passed to the logger
  # file is the full filepath to the file in question
  # profile data is an array of wall-time, cpu-time and number-of-calls as integers
  # line is the line in question (actual line of code from the file)
  # num is the line number
  def self.format_line(file, profile_data, line, num)
    @@formatter.call file, profile_data, line, num
  end

  # profile the provided block.
  # regex is a regex for which files to include in the profile
  # when full_trace is set to false, it will ignore anything inside ~/.rvm directory
  # by default this will spit out a profile to the log, which is great when in development mode
  def self.profile(regex=/./, full_trace=false, &block)
    $:.unshift Rails.root + 'vendor/rblineprof/ext'
    require 'rblineprof'

    profile = lineprof(regex) do
      block.call
    end

    profile.each do |file, p|
      # skip over anything that's a gem:
      next if !full_trace && file.match(/\/\.rvm\//) # anything in the .rvm directory
      next if file.match(/^\(/) # anything that starts with a paren

      # identify the file in the logger
      self.log_line "\n/// #{ file } ===>>>"

      # log each line from the file with profile data
      File.readlines(file).each_with_index do |line, num|
        self.log_line( self.format_line(file, profile[file][num+1], line, num) )
      end
    end
  end
end