Idle Hacking

I've been doing a little work on mongrel-esi to improve it's concurrency. Here's a little test script I wrote to verify some of my thinking. The tricky part, is keeping all the bytes in the correct order, while still requesting as much as possible in parallel. Here's my thinking at the moment.

# reading a file
# as we read and encounter <esi:include src="/foo"/>
# spawn a thread and simulate requesting, but continue parsing the file looking for more on the main thread
# tweak the sleep calls to get different behavior...
require 'thread'

# define a sample buffer here:
input_stream = %Q(
  hello there world

  <esi:include src='/foo/'/>

  some more bytes here
  
  <esi:include src='/bar/'/>

  and some more here
)

# lets read line by line

count = 0
output = []
back_buffer = []
lock = Mutex.new
in_request = false
requesting = []
last_out = 0

input_stream.split("\n").each do|line|
  if line.match(/<esi:/)
    lock.synchronize do
      in_request = true
      back_buffer[count] = nil # reserve a location in back_buffer
    end
    requesting << Thread.new(count) do|id|
      sleep 0.4 # some busy work
      lock.synchronize do
        back_buffer[id] = "#{id}: sample"
        in_request = false
      end
    end
  else
    sleep 0.1
    lock.synchronize do
      if in_request 
        puts "buffering lines..."
        back_buffer[count] = "#{count}: #{line}"
      else
        # roll up requests
        puts "roll up requests..."
        i = 0
        until i == count
          o = back_buffer.shift
          output << o unless o.nil?
          i += 1
        end
        output << "#{count}: #{line}"
        last_out = count # mark the last buffer in back_buffer to be sent
      end
    end
  end
  count += 1
end
requesting.each do|t|
  t.join
end
# roll up requests
while !back_buffer.empty?
  o = back_buffer.shift
  output << o unless o.nil?
end

puts back_buffer.inspect
puts output.join("\n")

One obvious issue with this implementation is the number of threads per request is bounded by the response document.
Update: I've checked the above into svn, with a few updates