Merb devel - Jul 2007 - streaming response

hello list!

I like merb a lot, it frees me from dropping to mongrel every time i
want to stream something.

i have an action which will stream a list of JSON objects (separated
by semicolons). unfortunately because of Mongrel''s write-only header
hash, once a Content-Length header has been written, I can never again
tell it to not send such a thing - and streaming doesn''t work if there
is a Content-Length header present.

I''ve been forced into returning a Proc like this from my action

      Proc.new do
        response.write("HTTP/1.1 200 OK\n")
        response.write("Cache-Control: no-cache\n")
        response.write("Pragma: no-cache\n")
        response.write("Content-type: text/json\n\n")

        while true
          sleep wait
          response.write json
        end
        response.done = true
      end

writing the headers myself. i''d much prefer to do something like this:

      Proc.new do
        response.send_status_no_connection_close(nil) # nil = no content-length
        response.send_header
        response.write("\n\n")

        while true
          sleep wait
          response.write json
        end
        response.done = true
      end

Does anyone have suggestions on how to clean up my code so that I
don''t need to touch raw HTTP?

Thanks! ry

On Jul 30, 2007, at 6:11 AM, ry dahl wrote:
> hello list!
>
> I like merb a lot, it frees me from dropping to mongrel every time i
> want to stream something.
>
> i have an action which will stream a list of JSON objects (separated
> by semicolons). unfortunately because of Mongrel''s write-only
header
> hash, once a Content-Length header has been written, I can never again
> tell it to not send such a thing - and streaming doesn''t work if
there
> is a Content-Length header present.
>
> I''ve been forced into returning a Proc like this from my action
>
>       Proc.new do
>         response.write("HTTP/1.1 200 OK\n")
>         response.write("Cache-Control: no-cache\n")
>         response.write("Pragma: no-cache\n")
>         response.write("Content-type: text/json\n\n")
>
>         while true
>           sleep wait
>           response.write json
>         end
>         response.done = true
>       end
>
> writing the headers myself. i''d much prefer to do something like
this:
>
>       Proc.new do
>         response.send_status_no_connection_close(nil) # nil = no  
> content-length
>         response.send_header
>         response.write("\n\n")
>
>         while true
>           sleep wait
>           response.write json
>         end
>         response.done = true
>       end
>
> Does anyone have suggestions on how to clean up my code so that I
> don''t need to touch raw HTTP?
>
> Thanks! ry

Hey Ry-

	You could wrap up that logic in a helper method like this:

class Merb::Controller
     def render_stream(&block)
       Proc.new do
         response.write("HTTP/1.1 200 OK\n")
         response.write("Cache-Control: no-cache\n")
         response.write("Pragma: no-cache\n")
         response.write("Content-type: text/json\n\n")
         block.call
         response.done = true
       end
     end
end

then use it in an action:

def someaction
   render_stream do
       streaming = true
       while streaming
          sleep wait
          response.write json
          streaming = false if some_condition
       end
   end
end


	Untested here so let me know how it works for you.

Cheers-
-- Ezra Zygmuntowicz 
-- Founder & Ruby Hacker
-- ez at engineyard.com
-- Engine Yard, Serious Rails Hosting
-- (866) 518-YARD (9273)