asyncio HTTP服务器挂断keepalive

我正在尝试使用asyncio编写一个HTTP/1服务器,并尝试让它处理HTTP keep alives。我有下面的代码。

import re
import socket
import asyncio

async def request_handler(reader, writer):
    try:
        keep_alive = True

        while keep_alive:
            keep_alive = False

            while True:
                print('Awaiting data')
                line = await reader.readline()
                print('Finished await got %s' % line)
                if not line.rstrip(b'\r\n'):
                    break

                if re.match(rb'connection:\s*keep-alive', line, re.I):
                    keep_alive = True

            writer.write(b'HTTP/1.1 200 OK\r\n\r\n<h1>My web page</h1>\r\n')
            await writer.drain()
    finally:
        writer.close()

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    coro = asyncio.start_server(request_handler, '', 8888, family=socket.AF_UNSPEC, loop=loop, limit=2048)
    server = loop.run_until_complete(coro) 

    try:
        loop.run_forever()
    finally:
        server.close()
        loop.run_until_complete(server.wait_closed())
        loop.close()

对于来自curl等工具的请求,可以在不挂断服务器的情况下正确地处理请求。

但是,尝试在浏览器中加载URL会导致服务器永远不会终止连接。浏览器试图请求两个资源,一个来自 / 一对一 /favicon.ico

我试着打印服务器接收到的数据。但是,服务器似乎从未收到第二个请求的数据:

Awaiting data
Finished await got b'GET / HTTP/1.1\r\n'
Awaiting data
Finished await got b'Host: localhost:8888\r\n'
Awaiting data
Finished await got b'Connection: keep-alive\r\n'
Awaiting data
Finished await got b'Upgrade-Insecure-Requests: 1\r\n'
Awaiting data
Finished await got b'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36\r\n'
Awaiting data
Finished await got b'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8\r\n'
Awaiting data
Finished await got b'Accept-Encoding: gzip, deflate, br\r\n'
Awaiting data
Finished await got b'Accept-Language: en-US,en;q=0.9\r\n'
Awaiting data
Finished await got b'\r\n'
Awaiting data

有人能告诉我问题出在哪里吗?