Recipe15.4.Enabling an XML-RPC Server to Be Terminated Remotely

Recipe 15.4. Enabling an XML-RPC Server to Be Terminated Remotely

Credit: Christoph Dietze, Brian Quinlan, Jeff Bauer

Problem

You are coding an XML-RPC server, using the Python Standard Library's SimpleXMLRPCServer module, and you want to make it possible for a remote client to cause the XML-RPC server to exit cleanly.

Solution

You have to use your own request-handling loop (instead of the serve_forever method of SimpleXMLRPCServer) so that you can stop looping when appropriate. For example:

import SimpleXMLRPCServer running = True def finis( ):     global running     running = False     return 1 server = SimpleXMLRPCServer.SimpleXMLRPCServer(('127.0.0.1', 8000)) server.register_function(finis) while running:     server.handle_request( )

Discussion

SimpleXMLRPCServer's serve_forever method, as its name implies, attempts to keep serving "forever"that is, it keeps serving until the whole server process is killed. Sometimes, it's useful to allow remote clients to request a clean termination of a service by remotely calling a server-exposed function, and this recipe demonstrates the simplest way to allow this functionality.

The finis function (which gets exposed to remote clients via the register_function call) sets the global variable running to False (and then returns something that is not None because the XML-RPC protocol cannot deal with the None object). Using the while running loop, instead of a serve_forever call, then ensures that the server stops serving and terminates when the variable running becomes false.

If you prefer to subclass SimpleXMLRPCServer, you can obtain a similar effect by overriding the serve_forever method: that is, instead of placing the simple while running: server.handle_request loop inline, you can code, for example (with the same function finis as in the recipe's Solution):

class MyServer(SimpleXMLRPCServer.SimpleXMLRPCServer):     def serve_forever(self):         while running:             self.handle_request( ) server = MyServer(('127.0.0.1', 8000)) server.register_function(finis) server.serve_forever( )

However, this alternative approach offers no special advantage (unless you have a fetish for being object oriented for no particular purpose), and, since this alternative approach is telling a little white lie (by using the name serve_forever for a method that does not keep serving "forever"!), the simpler approach in the recipe's Solution can definitely be recommended.

See Also

The SimpleXMLRPCServer module is part of the Python Standard Library and is documented in a chapter of the Library Reference portion of Python's online documentation.