Test of experimental Tornado feature for a streaming request body handler

client.py

# 
# Test of experimental Tornado feature for a streaming request body handler, see
# https://github.com/nephics/tornado/commit/1bd964488926aac9ef6b52170d5bec76b36df8a6
#

#
#  Client sending file to server
#

import tornado.httpclient as httpclient

with open('test.pdf', 'r') as f:
    body = f.read()

http_client = httpclient.HTTPClient()
request = httpclient.HTTPRequest('http://localhost:8888', 'POST', body=body,
                                 headers={'Content-Type': 'application/pdf'})
try:
    response = http_client.fetch(request)
    print('File uploaded, server response: {0}'.format(response.body))
except httpclient.HTTPError, e:
    print "Error:", e

server.py

# 
# Test of experimental Tornado feature for a streaming request body handler, see
# https://github.com/nephics/tornado/commit/1bd964488926aac9ef6b52170d5bec76b36df8a6
#

#
#  Server with request handler reading of file stream from client
#


import tornado.ioloop
import tornado.web
import uuid


@tornado.web.stream_body
class MainHandler(tornado.web.RequestHandler):
    def post(self):
        # open a file or a socket to stream the uploaded data to
        self.fp = open('file_{0}'.format(uuid.uuid1().hex), 'w')
        self.request.request_continue()
        self.read_bytes = 0
        self._read_chunk()

    def _read_chunk(self):
        # set the chunk size and read bytes from the stream
        chunk_length = min(10000,
            self.request.content_length - self.read_bytes)
        if chunk_length > 0:
            self.request.connection.stream.read_bytes(
                chunk_length, self._on_chunk)
        else:
            self.fp.close()
            self._on_uploaded()

    def _on_chunk(self, chunk):
        if chunk:
            # write chunk of data to disk
            self.fp.write(chunk)
            self.read_bytes += len(chunk)
        else:
            # no more incoming data, set correct content_length
            self.content_length = self.read_bytes
        self._read_chunk()

    def _on_uploaded(self):
        self.write("Uploaded!")
        self.finish()

if __name__ == "__main__":
    application = tornado.web.Application([
        (r"/", MainHandler),
    ])
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()

Hello,

Can this example be used to stream the file from form upload to MongoDB GridFS ?

:self-answer:
Yes, it can.