From: Paul Danos <pdrizzle@...>
Date: 2009-11-18T09:06:19+09:00
Subject: EventMachine: dynamic "client" connections

Thanks for reading this and thanks in advance if you provide any help!

I'm new to Ruby.  Trying to write a distributed file system consisting
of a Metadata Server (MS), Object Servers (OS), and clients.  I'm able
to bring up a MS and an OS that registers with the MS. What I'm having
trouble with is sending a request from a client to the MS, which should
then send that request to the appropriate OS in order to serve the
client.  The requests are simple download, upload, and delete commands.
This is what I would like to have happen (for example, an upload):
1. client sends the upload command to the MS (?)
2. MS finds a an OS with available space to upload to (I have this
working)
3. MS sends the client's request and IP to the OS (?)
4. OS contacts the client (?)
5. client uploads file to OS (I figured out how to stream files)

So I need a way to dynamically create a connection to a variable IP and
send a variable message across it in order to do numbers 1, 3 & 4.  I've
tried working with EventMachine in classes and modules, but cannot
figure out how to pass variables to it dynamically.

Here is an example of one of my many attempts at this:

######################################################

class SendCommand < EM::Connection
  attr_accessor :cmd, :file

  def post_init
    puts "Sending: #{@cmd} #{@file}"
    send_data("#{@cmd} #{@file}")
  end
end


class ConnectToMS

  def initialize(cmd, file)
    @cmd = cmd
    @file = file
  end

  def connect_to_ms
    host = '127.0.0.1'
    port = 6666
    EM.run do
      EM.connect(host, port, SendCommand) do |con|
        con.cmd = @cmd
        con.file = @file
      end
      puts "Sending command: #{@cmd} File: #{@file}"
    end
  end

end


######################################################

Then I would call it like this:

c = ConnectToMS.new("UPLOAD","file_name")
c.connect_to_ms
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