Yes - very similar. In my case, I'm waiting for a long running query. Flask is executing behind AWS ELB -> nginx -> uwsgi -> flask. The ELB enforces a 60s timeout and I was hoping to use stream_with_context to transmit content using chunks to keep the connection open while my query executes. My test results calling at each of the layers:

ELB - times out after 60s
Nginx - appears to buffer all the content and then return the response
Flask (directly using the werkzeug server) - Returns an HTTP 1.0 header (see after the fragment) and then transmits content until complete

Here's the code snippet I am using for experimenting:

from flask import Flask, Response, stream_with_context
import time

app = Flask(__name__)

@app.route('/streamit', methods=['GET'])
def streamit():
    def generator():
        for x in xrange(70):
            time.sleep(1.0)
            yield ' '
        yield '<html><body>done</body></html>'
    return Response(stream_with_context(generator()))

if __name__ == '__main__':
    app.run()

# Run this script and then testing using:
#   curl -v -N http://localhost:5000/streamit

Curl output:

$ curl -v -N http://localhost:5000/streamit
* About to connect() to localhost port 5000 (#0)
*   Trying ::1...
* Adding handle: conn: 0x7f96d180aa00
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x7f96d180aa00) send_pipe: 1, recv_pipe: 0
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 5000 (#0)
> GET /streamit HTTP/1.1
> User-Agent: curl/7.33.0
> Host: localhost:5000
> Accept: */*
> 
* HTTP 1.0, assume close after body
< HTTP/1.0 200 OK
< Content-Type: text/html; charset=utf-8
< Connection: close
< Server: Werkzeug/0.9.3 Python/2.7.5
< Date: Mon, 27 Jan 2014 22:48:30 GMT
< 
                                                                      <html><body>done</body></html>* Closing connection 0

Uh oh!

support for HTTP/1.1 Transfer-Encoding: chunked #367

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