Response streaming does not work

The following code inspired by the documentation does not work. The result is buffered and sent to the client at once.

import cherrypy
import time

class Root:
    @cherrypy.expose
    def thing(self):
        cherrypy.response.headers['Content-Type'] = 'text/plain'
        def content():
            yield "Hello, "
            time.sleep(3)
            yield "world"
        return content()
    thing._cp_config = {'response.stream': True}

print(cherrypy.__version__)
cherrypy.quickstart(Root())

[stenci]

In Windows all the clients seem to buffer, so it seems to be a lower level problem in Windows.

Both Firefox and curl on Linux stream the output as expected, regardless of whether the CherryPy server runs on Windows or Linux.

Both Firefox and curl on Windows buffer the output. The output of curl on Windows shows the correct timestamps, but the whole content is displayed at once at the end.

The documentation already says:

In general, it is safer and easier to not stream output

Perhaps it is worth adding:

… and it doesn’t work well in Windows clients

I will run my scripts from Firefox running on Ubuntu on VirtualBox, so I can keep track of the progress without rewriting them. It’s an horrible workaround, but it’s the easiest way for me.

Thanks for your help

[webknjaz]

I’ve already confirmed that it is working. You may check this with command I posted above.

Here’s handler yielding additional timestamps:

#! /usr/bin/env python

from datetime import datetime
import time
import cherrypy

class Root:
    @cherrypy.expose
    @cherrypy.config(**{'response.stream': True})
    def thing(self):
        cherrypy.response.headers['Content-Type'] = 'text/plain'
        yield 'Hi, ' * 100
        yield str(datetime.now())
        yield '================='
        time.sleep(3 * 2)
        yield str(datetime.now())
        yield 'there!'


if __name__ == '__main__':
    cherrypy.quickstart(Root())

$ curl --trace-ascii - localhost:8080/thing
== Info:   Trying ::1...
== Info: connect to ::1 port 8080 failed: Connection refused
== Info:   Trying 127.0.0.1...
== Info: Connected to localhost (127.0.0.1) port 8080 (#0)
=> Send header, 83 bytes (0x53)
0000: GET /thing HTTP/1.1
0015: Host: localhost:8080
002b: User-Agent: curl/7.46.0
0044: Accept: */*
0051: 
<= Recv header, 17 bytes (0x11)
0000: HTTP/1.1 200 OK
<= Recv header, 24 bytes (0x18)
0000: Server: CherryPy/8.1.0
<= Recv header, 39 bytes (0x27)
0000: Content-Type: text/html;charset=utf-8
<= Recv header, 37 bytes (0x25)
0000: Date: Mon, 19 Sep 2016 18:22:41 GMT
<= Recv header, 28 bytes (0x1c)
0000: Transfer-Encoding: chunked
<= Recv header, 2 bytes (0x2)
0000: 
<= Recv data, 439 bytes (0x1b7)
0000: 190
0005: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
0045: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
0085: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
00c5: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
0105: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
0145: Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 
0185: Hi, Hi, Hi, Hi, 
0197: 1a
019b: 2016-09-19 21:22:41.744041
Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, Hi, 2016-09-19 21:22:41.744041<= Recv data, 23 bytes (0x17)
0000: 11
0004: =================
=================<= Recv data, 32 bytes (0x20)
0000: 1a
0004: 2016-09-19 21:22:47.750253
2016-09-19 21:22:47.750253<= Recv data, 11 bytes (0xb)
0000: 6
0003: there!
there!<= Recv data, 5 bytes (0x5)
0000: 0
0003: 
== Info: Connection #0 to host localhost left intact

Do you see timestamps? Their difference is 6 seconds. The output to console has stopped for 6 seconds as in handler too. This is my proof.

So look for bottlenecks in your scripts.