Rails 3.2 streaming

Question

I am working on a streaming download (CSV) from Rails 3.2 and am coming up against an issue of the initial page request taking a long time. The following controller code ill

Answer 1

The edited question turned out to contain exactly the answer I needed. Posting it here as an answer.

The answer to getting the Rack handler to stream properly is apparently to add a Last-Modified header to the response:

self.response.headers['Last-Modified'] = Time.now.ctime.to_s