SocketServer, its offspring, and threads

[eliben]

On May 25, 5:40 pm, eliben <eli... at gmail.com> wrote:
> Hello,
>
> I have a small wxPython application. Today I was trying to add some
> RPC capability to it, so I implemented an instance of
> SimpleXMLRPCServer that runs in a separate thread when invoked and
> answers requests.
>
> All went fine until I realized that I have to sometimes stop the
> server - which is where I ran into a problem. Python threads can not
> be killed after they've been started. They can be kindly requested to
> end, but it's up to the thread itself to decide when it wants to
> finish. At least this is my understanding. It probably makes sense,
> because threads can hold resources which can't just be dropped
> suddenly, and have to be cleaned in a proper manner. (Does this sound
> like the truth ?)
>
> Anyway, this creates a problem because SimpleXMLRPCServer likes to
> block and never return. I dug deeper and found out that all offspring
> of SocketServer can only handle requests in a blocking manner. Even if
> you call handle_request( ) and not serve_forever(), it will block
> until a request is received and handled. This means that a
> SocketServer object running in a thread blocks the thread, and this
> thread can not be stopped.
>
> Is there any graceful solution to this problem ?
>
> I suppose I can use sockets in non-blocking mode, or use select(), but
> this will mean I will have to implement my server with raw sockets and
> not a handy helper like SocketServer. For the XML-RPC server I want
> this is a headache, as I will probably have to implement my own XML-
> RPC server based on raw non-blocking sockets.
>
> Thanks in advance for any ideas and suggestions
> Eli


I ended up using an ugly hack to make it work for me. Since
handle_request() only blocks until a request is received, the thread
can be unblocked by sending it a real message. So to stop a server, I
opened a XML-RPC client connection (using ServerProxy from xmlrpclib)
and made a request. In the server thread, handle_process() returned
and the thread could see the flag requesting it to stop.

There must be a better way ! Any ideas ?

Eli