From: Robert Leftwich <robert@...>
Date: 2003-01-06T07:35:11+09:00
Subject: Webrick threading issue?

I am learning Ruby as a prototyping/spiking/development tool and have a 
problem with one task I have set myself. The scenario is that I have a 
Webrick (v1.2.3) http server using Ruby 1.6.7 on W2000. Webrick is setup to 
handle a posted XML document that contains a list of recipients for a piece 
of information and what I want to do is to use an Http Post to send that 
information to each of those recipients. As a test setup I have the same 
Webrick server being the recipient as well as the source of the data. A 
diagram might help -

Client (Http Post)--> Webrick (http://localhost:2000/notifications) body = 
<recipient href="http://localhost:2000/incoming"/><data>...</data>

Webrick (Http Post) --> Webrick (http://localhost:2000/incoming) body = 
<data>...</data>

The problem is that the second post never works and fails with an error as 
follows:

[2003-01-06 07:54:18] ERROR Errno::EINVAL: Invalid argument
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:299:in `write'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:299:in `<<'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:299:in 
`_write_data'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:271:in 
`send_body_string'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:165:in 
`send_body'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpresponse.rb:85:in 
`send_response'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/httpserver.rb:57:in `run'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:154:in `start_thread'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:148:in `start'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:148:in `start_thread'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:106:in `start'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:101:in `each'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:101:in `start'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:91:in `start'
         e:/ruby/lib/ruby/site_ruby/1.6/webrick/server.rb:91:in `start'

I am guessing that the first post blocks the receipt of the second post 
until it times out, but I would have thought the server could handle more 
than one post on a different uri.

The relevant server code snippets are below and I apologize in advance for 
any glaringly obvious newbie problems!

Robert





==================================================================================================
# a servlet for handling the message notifications
class MessageNotificationsServlet < HTTPServlet::FileHandler

   @recipientQueue

    def initialize(server, root, show_dir=false)
   	super(server, root, show_dir)
	@recipientQueue = SizedQueue.new( 50 )
	Thread.new( @recipientQueue ) { |aRecipientQueue|
		while true
			aRecipient = aRecipientQueue.pop()
			h = Net::HTTP.new('localhost', 2000)
			resp, reply = h.post2( aRecipient[0] + IN_RESOURCE, aRecipient[1], { 
"Content-Type"=> "text/plain" } )
		end
	}
   end

   def do_POST(request, response)
	notificationDoc = Document.new request.body
	notificationDoc.elements.each("//recipient") { |element| 
element.attributes["status"] = "Pending" }
	item = notificationDoc.root.elements["//item"]
	recipientElements = notificationDoc.elements.to_a('//recipient')
	recipientElements.each { |element|
			recipientArray = [ element.attributes["href"], item, f.path ]
			@recipientQueue.push( recipientArray )
	}
	response.status = 202
   end
   end
end

# a servlet for handling an inbox
class InboxServlet < HTTPServlet::FileHandler

   def do_POST(request, response)
	puts request.body )
	response.status = 202
	response['Content-Type'] = "text/plain"
	response.body = "Your notification will be stored until it is retrieved by 
the recipient."
   end
end

httpServer = HTTPServer.new( :Port => 2000 )
httpServer.mount("/notifications", MessageNotificationsServlet, 
"./notifications", false)
httpServer.mount("/incoming", InboxServlet, "./incoming", false)
trap("INT"){ httpServer.shutdown }
httpServer.start