From: Brian Candler <b.candler@...>
Date: 2009-02-25T22:21:12+09:00
Subject: Re: Feeding data to be PUT with Net::HTTP?

Chris Markle wrote:
> Since I am HTTP PUT'ing large amounts of data (ideally using Net::HTTP)
> I would like to feed data in some way to an HTTP PUT so that I don't
> have to have the entire amount of data in memory before using methods
> like request or send_request to initiate the PUT. I saw one post that
> suggests it can't be done but I thought I'd check again.

Best way to understand this is to go to the source code - probably 
somewhere like /usr/lib/ruby/1.8/net/http.rb on your system.

    def put(path, data, initheader = nil)   #:nodoc:
      res = request(Put.new(path, initheader), data)
      res.value unless @newimpl
      res
    end

Trace it through, this calls req.exec to send the request.

    def exec(sock, ver, path)   #:nodoc: internal use only
      if @body
        send_request_with_body sock, ver, path, @body
      elsif @body_stream
        send_request_with_body_stream sock, ver, path, @body_stream
      else
        write_header sock, ver, path
      end
    end

Looking at send_request_with_body_stream, you can pass any object which 
responds to read(n), such as an open IO stream. If you set 
"Tranfer-Encoding: chunked" then you'll get it posted in chunks too, 
which simplifies buffering at the receiving side (if it also supports 
chunking)

But it looks like you may need to create your Request object by hand and 
call #body_stream=, because set_body_internal doesn't understand about 
streaming objects. Perhaps something like this (untested):

  req = Net::HTTP::Put.new(path)
  req.body_stream = File.open("/path/to/large/file")
  res = Net::HTTP.start(url.host, url.port) {|http|
      http.request(req)
  }

HTH,

Brian.
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