Export MongoDB system.profile collection to csv format with some friendly visualization

Gemfile

source "https://rubygems.org"

gem "mongo", "~> 1.8.2"
gem "bson_ext", "~> 1.8.2"
gem "actionpack", "~> 3.2.12"

profiling.rb

require "rubygems"
require "bundler/setup"

require "action_view"
require "mongo"

include ActionView::Helpers::NumberHelper
include Mongo

log_file = "log-#{Time.now.to_i}.csv"

report  = %w(port ts ns query ntoreturn responseLength friendly millis nscanned nreturned ratio)
fields  = %w(ts ns query ntoreturn responseLength millis nscanned nreturned)

host = "localhost"
port = 27017
database = "db"

File.open(log_file, "w") do |f|
  f.puts report.join(",")

  @client = MongoClient.new(host, port, :read => :secondary)
  @db     = @client[database]
  @coll   = @db["system.profile"]

  @coll.find({ "nscanned" => { "$exists" => true, "$gt" => 0 }, "millis" => { "$gt" => 1 } }, { fields: fields }).each do |doc|
    values = fields.map do |f|
      case f
      when "responseLength"
        [doc[f], number_to_human_size(doc[f])]
      else
        doc[f]
      end
    end

    values.unshift(port)
    values << number_to_percentage(doc["nreturned"] * 100 / doc["nscanned"].to_f)

    f.puts values.flatten.map { |v| "\"#{v.to_s.gsub('"', "'")}\"" }.join(",")
  end
end