gistfile1.rb

  def emit(tag, es, chain)
    t = if @sample_unit == :all
          'all'
        else
          tag
        end
    # Access to @counts SHOULD be protected by mutex, with a heavy penalty.
    # Code below is not thread safe, but @counts (counter for sampling rate) is not
    # so serious value (and probably will not be broke...),
    # then i let here as it is now.
    interval = @interval
    pairs = []
    es.each {|time,record|
      c = @counts.fetch(t, 0) + 1
      if c % interval == 0
        @counts[t] = 0 if c > 0x6fffffff
        pairs.push [time, record]
      end
    }
    emit_sampled(tag, pairs)

    chain.next
  end