CODEWITHSUNDEEP
pythonmultithreadingsocketsshutdownrequesthandler
user7610
user7610

Reputation: 28811

How do I forcibly disconnect all currently connected clients to my TCP or HTTP server during shutdown?

I have a fake HTTP server that I use as a fixture in my testing. At some point in the test, I want to stop the server regardless of any still open connections. Clients on these open connections should get a TCP FIN.

I am aware that usually production servers need to solve different problem, that of quiescing, sometimes called graceful shutdown. This is the opposite of what I want.

With a standalone process, it is usually possible to simply get the process to quit and the OS will take care of the rest. (Forcibly killing processes is easy, while forcibly killing threads is not.) My fake server is, however, running in a thread of the test process itself, so I don't have this option (and I don't want to externalize it if there is other way around).

I investigated this issue in Python, with the HTTPServer class, where I was not able to find any solution.

I also investigated this in Go, where I was able to find the concept of Contexts, which is close to what I need, but it works the other way around: a http server would propagate a Context that can be used to cancel e.g. a database lookup if a client disconnected.

Edit: looks like Go actually does what I need and has a separate graceful and nongraceful shutdown methods, with the nongraceful being net/http#Server.Close.

server = http.server.HTTPServer(...)
thread = threading.Thread(run=server.serve_forever)
thread.start()

# a client has connected ....

server.shutdown()
# at this point I want to have the server stopped,
# without waiting for the request handling to complete

Upvotes: 0

Views: 807

Answers (1)

user7610
user7610

Reputation: 28811

I've implemented the Go solution in Python. When new client connects, I remember the client socket, and when I want to quit, I shutdown all remembered sockets.

It seems to work.

import socket
import http.server.HTTPServer

class MyHTTPServer(HTTPServer):
    """Adds a method to the HTTPServer to allow it to exit gracefully"""

    def __init__(self, addr, handler_cls):
        super().__init__(addr, handler_cls)
        self._client_sockets: List[socket.socket] = []

        self.server_killed = False

    def get_request(self) -> Tuple[socket.socket, Any]:
        """Remember the client socket"""
        sock, addr = super().get_request()
        self._client_sockets.append(sock)
        return sock, addr

    def shutdown_request(self, request: socket.socket) -> None:
        """Forget the client socket"""
        self._client_sockets.remove(request)
        print(f"{self._client_sockets=}")
        super().shutdown_request(request)

    def force_disconnect_clients(self) -> None:
        """Shutdown the remembered sockets"""
        for client in self._client_sockets:
            client.shutdown(socket.SHUT_RDWR)

Usage

server = MyHTTPServer(server_addr, MyRequestHandler)

# in a new thread
while not server.server_killed:
    self._server.handle_request()

# ... use the server (keep in mind it can have at most one client at a time) ...

# in the main program
server.server_killed = True
server.force_disconnect_clients()
server.server_close()

Upvotes: 0

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