Shutting down python TCPServer by custom handler

Question

I'm trying to shutdown a TCPServer from the SocketServer module through a GET request by the client, emitted when the window is closed, however the following code fails to initiate the shutdown:

def show_webgl(data):
    import SocketServer
    import SimpleHTTPServer
    from webbrowser import open

    PORT = 8000
    RUNNING = True

    class CustomHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
        def do_GET(self):
            if self.path=='/atom.json':
                # return data
                return
            elif self.path == '/shutdown':
                httpd.shutdown()
                # quit server, this line is never reached
            else:
                # serve other files
                SimpleHTTPServer.SimpleHTTPRequestHandler.do_GET(self)


    SocketServer.BaseServer.allow_reuse_address = True
    httpd = SocketServer.TCPServer(('0.0.0.0', 8000), CustomHandler)

    print "serving at port", PORT
    open('http://localhost:8000/three.html')
    httpd.serve_forever()     

    print 'closed'

Answer 1

Solution 1

Use a ThreadingHTTPServer.

class ThreadingHTTPServer(SocketServer.ThreadingMixIn, BaseHTTPServer.HTTPServer):
    allow_reuse_address = True

Your code:

import SocketServer
import SimpleHTTPServer
import BaseHTTPServer
from webbrowser import open
import hanging_threads

PORT = 8005
RUNNING = True

class CustomHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
    def do_GET(self):
        print "GET"
        if self.path=='/atom.json':
            # return data
            return
        elif self.path == '/shutdown':
            httpd.shutdown()
            print 'shutdown'
            # quit server, this line is never reached
        else:
            # serve other files
            SimpleHTTPServer.SimpleHTTPRequestHandler.do_GET(self)


class ThreadingHTTPServer(SocketServer.ThreadingMixIn, BaseHTTPServer.HTTPServer):
    allow_reuse_address = True

httpd = ThreadingHTTPServer(('0.0.0.0', PORT), CustomHandler)

print "serving at port", PORT
open('http://localhost:{}/three.html'.format(PORT))
httpd.serve_forever()

print 'closed'

Solution 2

start a thread with shutdown.

import threading
threading.Thread(target = httpd.shutdown).start()

Context

This is where it hangs. Using hanging_threads.py

    httpd.serve_forever()
  File "C:\Python27\lib\SocketServer.py", line 238, in serve_forever
    self._handle_request_noblock()
  File "C:\Python27\lib\SocketServer.py", line 295, in _handle_request_noblock
    self.process_request(request, client_address)
  File "C:\Python27\lib\SocketServer.py", line 321, in process_request
    self.finish_request(request, client_address)
  File "C:\Python27\lib\SocketServer.py", line 334, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "C:\Python27\lib\SocketServer.py", line 649, in __init__
    self.handle()
  File "C:\Python27\lib\BaseHTTPServer.py", line 340, in handle
    self.handle_one_request()
  File "C:\Python27\lib\BaseHTTPServer.py", line 328, in handle_one_request
    method()
  File "C:/Users/wollknaeul/Desktop/httpservertest.py", line 17, in do_GET
    httpd.shutdown()
  File "C:\Python27\lib\SocketServer.py", line 251, in shutdown
    self.__is_shut_down.wait()
  File "C:\Python27\lib\threading.py", line 618, in wait
    self.__cond.wait(timeout)
  File "C:\Python27\lib\threading.py", line 339, in wait
    waiter.acquire()

Some code:

def serve_forever(self, poll_interval=0.5):
    """Handle one request at a time until shutdown.

    Polls for shutdown every poll_interval seconds. Ignores
    self.timeout. If you need to do periodic tasks, do them in
    another thread.
    """
    self.__is_shut_down.clear()
    try:
        while not self.__shutdown_request:
            # XXX: Consider using another file descriptor or
            # connecting to the socket to wake this up instead of
            # polling. Polling reduces our responsiveness to a
            # shutdown request and wastes cpu at all other times.
            r, w, e = _eintr_retry(select.select, [self], [], [],
                                   poll_interval)
            if self in r:
                self._handle_request_noblock()
    finally:
        self.__shutdown_request = False
        self.__is_shut_down.set()

def shutdown(self):
    """Stops the serve_forever loop.

    Blocks until the loop has finished. This must be called while
    serve_forever() is running in another thread, or it will
    deadlock.
    """
    self.__shutdown_request = True
    self.__is_shut_down.wait()

So self._handle_request_noblock() calls your method and then shutdown() which waits for the server to leave serve_forever(). Can not happen.