Instrument thin to measure wait time inside its internal queue.

thin_connection.rb

module Thin
  class Connection < EventMachine::Connection
    attr_accessor :init_ts, :data_ts

    def initialize
      super
      @init_ts = Time.now
      Gravity.metrics.increment 'thin.connection'
    end

    alias_method :_receive_data, :receive_data
    def receive_data(data)
      unless @data_ts
        @data_ts = Time.now
        wait_time = ((@data_ts - @init_ts) * 1000.0).to_i
        Rails.logger.info "Processing request from #{remote_address}, thin.wait_time=#{wait_time}ms"
      end
      _receive_data(data)
    end
  end
end