Python HTTP-Server and Threading

Question

I tried to create a HTTP-server in Python using Threading:

from socketserver import ThreadingMixIn
from http.server import HTTPServer, BaseHTTPRequestHandler
import time, threading

class ThreadingServer(ThreadingMixIn, HTTPServer):
    pass
class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        print("do")
        time.sleep(10)
        message =  threading.currentThread().getName()
        self.wfile.write(message)
        self.wfile.write('\n')

if __name__ == "__main__":
    httpd = ThreadingServer( (host, port), Handler)
    httpd.serve_forever()

The server works well, but if two request are same time, they are executed sequentially. So the second request not executed until the first is finished.

When you say "they are executed sequentially": if you send two requests (quickly after one-another), does it take ~20s for both to return? — Pritam Baral
– Pritam Baral, Commented Mar 15, 2014 at 8:00
The problem is that ThreadingMixIn is sequencing your handler. Unfortunately a moderator deleted my answer, even though your question is not an exact duplicate. I will try posting again. — personal_cloud
– personal_cloud, Commented Sep 14, 2017 at 7:07

personal_cloud · Accepted Answer · 2017-09-14 21:30:10Z

1

That is absolutely right: ThreadingMixIn will make your entire handler sequential.

Instead, you need something like this:

import time, socket, threading

sock = socket.socket (socket.AF_INET, socket.SOCK_STREAM)
host = socket.gethostname()
port = 8000

sock.bind((host, port))
sock.listen(1)

HTTP = "HTTP/1.1 200 OK\nContent-Type: text/html; charset=UTF-8\n\n"

class Listener(threading.Thread):

    def __init__(self):
        threading.Thread.__init__(self)
        self.daemon = True # stop Python from biting ctrl-C
        self.start()

    def run(self):
        conn, addr = sock.accept()
        conn.send(HTTP)

        # serve up an infinite stream
        i = 0
        while True:
            conn.send("%i " % i)
            time.sleep(0.1)
            i += 1

[Listener() for i in range(100)]
time.sleep(9e9)

You can even use the above approach without writing your own HTTP server:

Python 2.7: streaming HTTP server supporting multiple connections on one port

edited Sep 14, 2017 at 21:30

answered Sep 14, 2017 at 7:08

personal_cloud

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2 Comments

WestCoastProjects Over a year ago

That's crucial information that the ThreadingMixin makes handler sequential. Can you add some reference info on that? It's amazing to me that this core class would be so hobbled. It explains a lot with my issues on python web servers.

personal_cloud Over a year ago

@javadba. I (and evidently others too) have spent some time trying to understand ThreadingMixIn... but, in software, at some point, you need to know what the original authors were thinking, and they didn't document HTTP streaming application... To me it seems some features of SocketServer are over-abstracted and therefore too much work to set up properly. IMO we've spent enough time on that, and effectively, for the time being, the answer is to just wrap BaseHTTPServer in your own thread launcher as I suggested.

Pritam Baral · Accepted Answer · 2014-03-15 07:59:40Z

0

Your code is written perfectly for multithreading in python. I see no reason why this would be sequential. You might wanna try random sleep intervals.

BTW: Python threads are not the same as OS threads. A normal python script runs in a single-process, single-threaded VM, as such only one python thread can be running at any time. (If you want to know more about this: look up GIL)

You can try using PyPy for true multithreading

edited Mar 15, 2014 at 7:59

answered Mar 15, 2014 at 7:31

Pritam Baral

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2 Comments

user3422533 Over a year ago

Thanks for your answer! But is there no other way to make a webserver in Python, which is able to response more then one request in same time. In the way I used in my example, each Handler-Object is running in a new thread. I hoped when they are running in two threads they can be execute the same time. (I hope you unserstand my english :| )

Pritam Baral Over a year ago

Your code seems fine for multithreading in python, and is exactly how it should be done; I do think something is going wrong that this exhibits sequential behaviour.

Liam M · Accepted Answer · 2014-03-15 08:16:56Z

0

Python is designed around a construct called the Global Interpreter Lock (GIL), which ensures that only one python instruction is run at any given time. This means that Python cannot run code in parallel, which explains why your code is being run in series. You can read more about the GIL here.

If you want to sidestep the GIL, then there is an option available to you: check out the multiprocessing package.

answered Mar 15, 2014 at 8:16

Liam M

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1 Comment

personal_cloud Over a year ago

Just because python is single-processing doesn't mean it can't have multiple asynchronous threads. A blocking I/O call will cause python to switch threads. The OP knows this and is right to use threading for that.

tnissi · Accepted Answer · 2015-08-11 06:21:56Z

0

I bumped into the same problem and found this oldish question. Turned out that for me the problem was that I was using Google Chrome, which seems to serialize the requests to the same URL. So the second request is not sent before the first one has had the response, and thus it seemed that the server was handling requests sequentially. Using curl -i <your URL here> worked much better.

answered Aug 11, 2015 at 6:21

tnissi

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Comments

MagMax · Accepted Answer · 2024-05-21 02:14:43Z

0

Just use http.server.ThreadingHTTPServer instead HTTPServer:

import time, threading
from http.server import ThreadingHTTPServer, BaseHTTPRequestHandler

class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        print("do")
        time.sleep(10)
        message =  threading.current_thread().name
        self.send_response(200)
        self.end_headers()
        self.wfile.write(message.encode())
        self.wfile.write(b'\n')

if __name__ == "__main__":
    host, port = '', 8001
    httpd = ThreadingHTTPServer( (host, port), Handler)
    httpd.serve_forever()

Note: I've changed some methods and transformed strings into bytes to avoid warnings and make it to work.

You can test it with:

for i in {1..10}; do curl localhost:8001/$i& ; done

answered May 21, 2024 at 2:14

MagMax

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1 Comment

Armando Contestabile Nov 11 at 16:57

Where have you used the class ThreadingHTTPServer in your code?

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