GameStar 2006 January/Gamestar_80_2006-01_dvd.iso/Dema/Civilization4/data1.cab/Civ4DemoComponent/Assets/Python/System/SocketServer.pyc

Python Compiled Bytecode | 2005-11-09 | 18.2 KB | 600 lines

# Source Generated with Decompyle++
# File: in.pyc (Python 2.4)

'''Generic socket server classes.

This module tries to capture the various aspects of defining a server:

For socket-based servers:

- address family:
        - AF_INET{,6}: IP (Internet Protocol) sockets (default)
        - AF_UNIX: Unix domain sockets
        - others, e.g. AF_DECNET are conceivable (see <socket.h>
- socket type:
        - SOCK_STREAM (reliable stream, e.g. TCP)
        - SOCK_DGRAM (datagrams, e.g. UDP)

For request-based servers (including socket-based):

- client address verification before further looking at the request
        (This is actually a hook for any processing that needs to look
         at the request before anything else, e.g. logging)
- how to handle multiple requests:
        - synchronous (one request is handled at a time)
        - forking (each request is handled by a new process)
        - threading (each request is handled by a new thread)

The classes in this module favor the server type that is simplest to
write: a synchronous TCP/IP server.  This is bad class design, but
save some typing.  (There\'s also the issue that a deep class hierarchy
slows down method lookups.)

There are five classes in an inheritance diagram, four of which represent
synchronous servers of four types:

        +------------+
        | BaseServer |
        +------------+
              |
              v
        +-----------+        +------------------+
        | TCPServer |------->| UnixStreamServer |
        +-----------+        +------------------+
              |
              v
        +-----------+        +--------------------+
        | UDPServer |------->| UnixDatagramServer |
        +-----------+        +--------------------+

Note that UnixDatagramServer derives from UDPServer, not from
UnixStreamServer -- the only difference between an IP and a Unix
stream server is the address family, which is simply repeated in both
unix server classes.

Forking and threading versions of each type of server can be created
using the ForkingServer and ThreadingServer mix-in classes.  For
instance, a threading UDP server class is created as follows:

        class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass

The Mix-in class must come first, since it overrides a method defined
in UDPServer! Setting the various member variables also changes
the behavior of the underlying server mechanism.

To implement a service, you must derive a class from
BaseRequestHandler and redefine its handle() method.  You can then run
various versions of the service by combining one of the server classes
with your request handler class.

The request handler class must be different for datagram or stream
services.  This can be hidden by using the mix-in request handler
classes StreamRequestHandler or DatagramRequestHandler.

Of course, you still have to use your head!

For instance, it makes no sense to use a forking server if the service
contains state in memory that can be modified by requests (since the
modifications in the child process would never reach the initial state
kept in the parent process and passed to each child).  In this case,
you can use a threading server, but you will probably have to use
locks to avoid two requests that come in nearly simultaneous to apply
conflicting changes to the server state.

On the other hand, if you are building e.g. an HTTP server, where all
data is stored externally (e.g. in the file system), a synchronous
class will essentially render the service "deaf" while one request is
being handled -- which may be for a very long time if a client is slow
to reqd all the data it has requested.  Here a threading or forking
server is appropriate.

In some cases, it may be appropriate to process part of a request
synchronously, but to finish processing in a forked child depending on
the request data.  This can be implemented by using a synchronous
server and doing an explicit fork in the request handler class
handle() method.

Another approach to handling multiple simultaneous requests in an
environment that supports neither threads nor fork (or where these are
too expensive or inappropriate for the service) is to maintain an
explicit table of partially finished requests and to use select() to
decide which request to work on next (or whether to handle a new
incoming request).  This is particularly important for stream services
where each client can potentially be connected for a long time (if
threads or subprocesses cannot be used).

Future work:
- Standard classes for Sun RPC (which uses either UDP or TCP)
- Standard mix-in classes to implement various authentication
  and encryption schemes
- Standard framework for select-based multiplexing

XXX Open problems:
- What to do with out-of-band data?

BaseServer:
- split generic "request" functionality out into BaseServer class.
  Copyright (C) 2000  Luke Kenneth Casson Leighton <[e-mail]>

  example: read entries from a SQL database (requires overriding
  get_request() to return a table entry from the database).
  entry is processed by a RequestHandlerClass.

'''
__version__ = '0.4'
import socket
import sys
import os
__all__ = [
    'TCPServer',
    'UDPServer',
    'ForkingUDPServer',
    'ForkingTCPServer',
    'ThreadingUDPServer',
    'ThreadingTCPServer',
    'BaseRequestHandler',
    'StreamRequestHandler',
    'DatagramRequestHandler',
    'ThreadingMixIn',
    'ForkingMixIn']
if hasattr(socket, 'AF_UNIX'):
    __all__.extend([
        'UnixStreamServer',
        'UnixDatagramServer',
        'ThreadingUnixStreamServer',
        'ThreadingUnixDatagramServer'])


class BaseServer:
    '''Base class for server classes.

    Methods for the caller:

    - __init__(server_address, RequestHandlerClass)
    - serve_forever()
    - handle_request()  # if you do not use serve_forever()
    - fileno() -> int   # for select()

    Methods that may be overridden:

    - server_bind()
    - server_activate()
    - get_request() -> request, client_address
    - verify_request(request, client_address)
    - server_close()
    - process_request(request, client_address)
    - close_request(request)
    - handle_error()

    Methods for derived classes:

    - finish_request(request, client_address)

    Class variables that may be overridden by derived classes or
    instances:

    - address_family
    - socket_type
    - allow_reuse_address

    Instance variables:

    - RequestHandlerClass
    - socket

    '''

    def __init__(self, server_address, RequestHandlerClass):
        '''Constructor.  May be extended, do not override.'''
        self.server_address = server_address
        self.RequestHandlerClass = RequestHandlerClass


    def server_activate(self):
        '''Called by constructor to activate the server.

        May be overridden.

        '''
        pass


    def serve_forever(self):
        '''Handle one request at a time until doomsday.'''
        while None:
            pass


    def handle_request(self):
        '''Handle one request, possibly blocking.'''

        try:
            (request, client_address) = self.get_request()
        except socket.error:
            return None

        if self.verify_request(request, client_address):

            try:
                self.process_request(request, client_address)
            self.handle_error(request, client_address)
            self.close_request(request)




    def verify_request(self, request, client_address):
        '''Verify the request.  May be overridden.

        Return True if we should proceed with this request.

        '''
        return True


    def process_request(self, request, client_address):
        '''Call finish_request.

        Overridden by ForkingMixIn and ThreadingMixIn.

        '''
        self.finish_request(request, client_address)
        self.close_request(request)


    def server_close(self):
        '''Called to clean-up the server.

        May be overridden.

        '''
        pass


    def finish_request(self, request, client_address):
        '''Finish one request by instantiating RequestHandlerClass.'''
        self.RequestHandlerClass(request, client_address, self)


    def close_request(self, request):
        '''Called to clean up an individual request.'''
        pass


    def handle_error(self, request, client_address):
        '''Handle an error gracefully.  May be overridden.

        The default is to print a traceback and continue.

        '''
        print '-' * 40
        print 'Exception happened during processing of request from', client_address
        import traceback
        traceback.print_exc()
        print '-' * 40



class TCPServer(BaseServer):
    """Base class for various socket-based server classes.

    Defaults to synchronous IP stream (i.e., TCP).

    Methods for the caller:

    - __init__(server_address, RequestHandlerClass)
    - serve_forever()
    - handle_request()  # if you don't use serve_forever()
    - fileno() -> int   # for select()

    Methods that may be overridden:

    - server_bind()
    - server_activate()
    - get_request() -> request, client_address
    - verify_request(request, client_address)
    - process_request(request, client_address)
    - close_request(request)
    - handle_error()

    Methods for derived classes:

    - finish_request(request, client_address)

    Class variables that may be overridden by derived classes or
    instances:

    - address_family
    - socket_type
    - request_queue_size (only for stream sockets)
    - allow_reuse_address

    Instance variables:

    - server_address
    - RequestHandlerClass
    - socket

    """
    address_family = socket.AF_INET
    socket_type = socket.SOCK_STREAM
    request_queue_size = 5
    allow_reuse_address = False

    def __init__(self, server_address, RequestHandlerClass):
        '''Constructor.  May be extended, do not override.'''
        BaseServer.__init__(self, server_address, RequestHandlerClass)
        self.socket = socket.socket(self.address_family, self.socket_type)
        self.server_bind()
        self.server_activate()


    def server_bind(self):
        '''Called by constructor to bind the socket.

        May be overridden.

        '''
        if self.allow_reuse_address:
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

        self.socket.bind(self.server_address)


    def server_activate(self):
        '''Called by constructor to activate the server.

        May be overridden.

        '''
        self.socket.listen(self.request_queue_size)


    def server_close(self):
        '''Called to clean-up the server.

        May be overridden.

        '''
        self.socket.close()


    def fileno(self):
        '''Return socket file number.

        Interface required by select().

        '''
        return self.socket.fileno()


    def get_request(self):
        '''Get the request and client address from the socket.

        May be overridden.

        '''
        return self.socket.accept()


    def close_request(self, request):
        '''Called to clean up an individual request.'''
        request.close()



class UDPServer(TCPServer):
    '''UDP server class.'''
    allow_reuse_address = False
    socket_type = socket.SOCK_DGRAM
    max_packet_size = 8192

    def get_request(self):
        (data, client_addr) = self.socket.recvfrom(self.max_packet_size)
        return ((data, self.socket), client_addr)


    def server_activate(self):
        pass


    def close_request(self, request):
        pass



class ForkingMixIn:
    '''Mix-in class to handle each request in a new process.'''
    active_children = None
    max_children = 40

    def collect_children(self):
        '''Internal routine to wait for died children.'''
        while self.active_children:
            if len(self.active_children) < self.max_children:
                options = os.WNOHANG
            else:
                options = 0

            try:
                (pid, status) = os.waitpid(0, options)
            except os.error:
                pid = None

            if not pid:
                break

            self.active_children.remove(pid)


    def process_request(self, request, client_address):
        '''Fork a new subprocess to process the request.'''
        self.collect_children()
        pid = os.fork()
        if pid:
            if self.active_children is None:
                self.active_children = []

            self.active_children.append(pid)
            self.close_request(request)
            return None
        else:

            try:
                self.finish_request(request, client_address)
                os._exit(0)
            except:

                try:
                    self.handle_error(request, client_address)
                finally:
                    os._exit(1)





class ThreadingMixIn:
    '''Mix-in class to handle each request in a new thread.'''
    daemon_threads = False

    def process_request_thread(self, request, client_address):
        '''Same as in BaseServer but as a thread.

        In addition, exception handling is done here.

        '''

        try:
            self.finish_request(request, client_address)
            self.close_request(request)
        except:
            self.handle_error(request, client_address)
            self.close_request(request)



    def process_request(self, request, client_address):
        '''Start a new thread to process the request.'''
        import threading
        t = threading.Thread(target = self.process_request_thread, args = (request, client_address))
        if self.daemon_threads:
            t.setDaemon(1)

        t.start()



class ForkingUDPServer(ForkingMixIn, UDPServer):
    pass


class ForkingTCPServer(ForkingMixIn, TCPServer):
    pass


class ThreadingUDPServer(ThreadingMixIn, UDPServer):
    pass


class ThreadingTCPServer(ThreadingMixIn, TCPServer):
    pass

if hasattr(socket, 'AF_UNIX'):

    class UnixStreamServer(TCPServer):
        address_family = socket.AF_UNIX


    class UnixDatagramServer(UDPServer):
        address_family = socket.AF_UNIX


    class ThreadingUnixStreamServer(ThreadingMixIn, UnixStreamServer):
        pass


    class ThreadingUnixDatagramServer(ThreadingMixIn, UnixDatagramServer):
        pass



class BaseRequestHandler:
    '''Base class for request handler classes.

    This class is instantiated for each request to be handled.  The
    constructor sets the instance variables request, client_address
    and server, and then calls the handle() method.  To implement a
    specific service, all you need to do is to derive a class which
    defines a handle() method.

    The handle() method can find the request as self.request, the
    client address as self.client_address, and the server (in case it
    needs access to per-server information) as self.server.  Since a
    separate instance is created for each request, the handle() method
    can define arbitrary other instance variariables.

    '''

    def __init__(self, request, client_address, server):
        self.request = request
        self.client_address = client_address
        self.server = server

        try:
            self.setup()
            self.handle()
            self.finish()
        finally:
            sys.exc_traceback = None



    def setup(self):
        pass


    def handle(self):
        pass


    def finish(self):
        pass



class StreamRequestHandler(BaseRequestHandler):
    '''Define self.rfile and self.wfile for stream sockets.'''
    rbufsize = -1
    wbufsize = 0

    def setup(self):
        self.connection = self.request
        self.rfile = self.connection.makefile('rb', self.rbufsize)
        self.wfile = self.connection.makefile('wb', self.wbufsize)


    def finish(self):
        if not self.wfile.closed:
            self.wfile.flush()

        self.wfile.close()
        self.rfile.close()



class DatagramRequestHandler(BaseRequestHandler):
    '''Define self.rfile and self.wfile for datagram sockets.'''

    def setup(self):
        import StringIO
        (self.packet, self.socket) = self.request
        self.rfile = StringIO.StringIO(self.packet)
        self.wfile = StringIO.StringIO()


    def finish(self):
        self.socket.sendto(self.wfile.getvalue(), self.client_address)