Python 3's http.server.HTTPServer has a one second delay on localhost

Question

I've got a client and a server running on the same box. The client is able to issue urllib.request.Request() commands to external URLs and get responses back in about 0.1 seconds, fast enough that as a user I'm not noticing any real delay. When issuing a Request() to my local http.server.HTTPServer() there's a 1 second delay between the client calling urllib.request.urlopen() and the server's do_GET(self) even getting the request.

I saw some answers suggest that it was an issue with DNS lookup for logging, and that overwriting address_string(self) would fix it, but I'm still seeing the exact same delay with or without the modification.

Server:

import http.server
import time

class MyHTTPHandler(http.server.BaseHTTPRequestHandler): 
    def do_GET(self):
        start = time.time()
        print(start)
        self.send_response(200)
        self.end_headers()

    def address_string(self):
        host, port = self.client_address[:2]
        return host  

server = http.server.HTTPServer(('localhost', 9999), MyHTTPHandler)
try:
    server.serve_forever()
except KeyboardInterrupt:
    print('Stopping server')

Client:

import urllib.request
import urllib.error
import time

def send_data():
    start = time.time()
    r = urllib.request.Request(url='http://localhost:9999')
    print(time.time())
    urllib.request.urlopen(r)
    print(time.time() - start)

while True:
    input('Press enter to send')
    send_data()

Any ideas what I'm missing to get rid of that one second delay? I'd like this basic server to respond at least as fast as a web server would.

Peter Horsley · Accepted Answer · 2018-05-28 11:43:39Z

4

It might seem strange, but try using 127.0.0.1 instead of localhost in your client.

answered May 28, 2018 at 11:43

Peter Horsley

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1 Comment

Stardidi Over a year ago

I was having the same issue on Windows 10, version 1809. Both a python flask server and a native application were responding over localhost with 5, 150 or 300ms delays (quite sequentially in that order). Switching it to 127.0.0.1 brought it down to a consistent 5ms

Dr. Cyanide · Accepted Answer · 2017-06-22 17:12:13Z

0

OK, so it looks like this might be a problem with Python versions.

Running Python 3.5.2 for Windows I get the 1 second delay. Running Python 3.4.3 for Ubuntu (technically Ubuntu for Windows) I get no delay.

edited Jun 22, 2017 at 17:12

answered Jun 17, 2017 at 14:36

Dr. Cyanide

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