LayoutTests/imported/w3c/web-platform-tests/websockets/handlers/send-backpressure_wsh.py

#!/usr/bin/python

import six
import time

# The amount of internal buffering a WebSocket connection has is not
# standardised, and varies depending upon the OS. Setting this number too small
# will result in false negatives, as the entire message gets buffered. Setting
# this number too large will result in false positives, when it takes more than
# 2 seconds to transmit the message anyway. This number was arrived at by
# trial-and-error.
MESSAGE_SIZE = 16 * 1024 * 1024


def web_socket_do_extra_handshake(request):
    # Turn off permessage-deflate, otherwise it shrinks our big message to a
    # tiny message.
    request.ws_extension_processors = []


def web_socket_transfer_data(request):
    # Send empty message to fill the ReadableStream queue
    request.ws_stream.send_message(b'', binary=True)

    # TODO(ricea@chromium.org): Use time.perf_counter() when migration to python
    # 3 is complete. time.time() can go backwards.
    start_time = time.time()

    # The large message that will be blocked by backpressure.
    request.ws_stream.send_message(b' ' * MESSAGE_SIZE, binary=True)

    # Report the time taken to send the large message.
    request.ws_stream.send_message(six.text_type(time.time() - start_time), binary=False)