• SocketServer.py


    """Generic socket server classes.
         2 
         3 This module tries to capture the various aspects of defining a server:
         4 
         5 For socket-based servers:
         6 
         7 - address family:
         8         - AF_INET{,6}: IP (Internet Protocol) sockets (default)
         9         - AF_UNIX: Unix domain sockets
        10         - others, e.g. AF_DECNET are conceivable (see <socket.h>
        11 - socket type:
        12         - SOCK_STREAM (reliable stream, e.g. TCP)
        13         - SOCK_DGRAM (datagrams, e.g. UDP)
        14 
        15 For request-based servers (including socket-based):
        16 
        17 - client address verification before further looking at the request
        18         (This is actually a hook for any processing that needs to look
        19          at the request before anything else, e.g. logging)
        20 - how to handle multiple requests:
        21         - synchronous (one request is handled at a time)
        22         - forking (each request is handled by a new process)
        23         - threading (each request is handled by a new thread)
        24 
        25 The classes in this module favor the server type that is simplest to
        26 write: a synchronous TCP/IP server.  This is bad class design, but
        27 save some typing.  (There's also the issue that a deep class hierarchy
        28 slows down method lookups.)
        29 
        30 There are five classes in an inheritance diagram, four of which represent
        31 synchronous servers of four types:
        32 
        33         +------------+
        34         | BaseServer |
        35         +------------+
        36               |
        37               v
        38         +-----------+        +------------------+
        39         | TCPServer |------->| UnixStreamServer |
        40         +-----------+        +------------------+
        41               |
        42               v
        43         +-----------+        +--------------------+
        44         | UDPServer |------->| UnixDatagramServer |
        45         +-----------+        +--------------------+
        46 
        47 Note that UnixDatagramServer derives from UDPServer, not from
        48 UnixStreamServer -- the only difference between an IP and a Unix
        49 stream server is the address family, which is simply repeated in both
        50 unix server classes.
        51 
        52 Forking and threading versions of each type of server can be created
        53 using the ForkingMixIn and ThreadingMixIn mix-in classes.  For
        54 instance, a threading UDP server class is created as follows:
        55 
        56         class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass
        57 
        58 The Mix-in class must come first, since it overrides a method defined
        59 in UDPServer! Setting the various member variables also changes
        60 the behavior of the underlying server mechanism.
        61 
        62 To implement a service, you must derive a class from
        63 BaseRequestHandler and redefine its handle() method.  You can then run
        64 various versions of the service by combining one of the server classes
        65 with your request handler class.
        66 
        67 The request handler class must be different for datagram or stream
        68 services.  This can be hidden by using the request handler
        69 subclasses StreamRequestHandler or DatagramRequestHandler.
        70 
        71 Of course, you still have to use your head!
        72 
        73 For instance, it makes no sense to use a forking server if the service
        74 contains state in memory that can be modified by requests (since the
        75 modifications in the child process would never reach the initial state
        76 kept in the parent process and passed to each child).  In this case,
        77 you can use a threading server, but you will probably have to use
        78 locks to avoid two requests that come in nearly simultaneous to apply
        79 conflicting changes to the server state.
        80 
        81 On the other hand, if you are building e.g. an HTTP server, where all
        82 data is stored externally (e.g. in the file system), a synchronous
        83 class will essentially render the service "deaf" while one request is
        84 being handled -- which may be for a very long time if a client is slow
        85 to read all the data it has requested.  Here a threading or forking
        86 server is appropriate.
        87 
        88 In some cases, it may be appropriate to process part of a request
        89 synchronously, but to finish processing in a forked child depending on
        90 the request data.  This can be implemented by using a synchronous
        91 server and doing an explicit fork in the request handler class
        92 handle() method.
        93 
        94 Another approach to handling multiple simultaneous requests in an
        95 environment that supports neither threads nor fork (or where these are
        96 too expensive or inappropriate for the service) is to maintain an
        97 explicit table of partially finished requests and to use select() to
        98 decide which request to work on next (or whether to handle a new
        99 incoming request).  This is particularly important for stream services
       100 where each client can potentially be connected for a long time (if
       101 threads or subprocesses cannot be used).
       102 
       103 Future work:
       104 - Standard classes for Sun RPC (which uses either UDP or TCP)
       105 - Standard mix-in classes to implement various authentication
       106   and encryption schemes
       107 - Standard framework for select-based multiplexing
       108 
       109 XXX Open problems:
       110 - What to do with out-of-band data?
       111 
       112 BaseServer:
       113 - split generic "request" functionality out into BaseServer class.
       114   Copyright (C) 2000  Luke Kenneth Casson Leighton <lkcl@samba.org>
       115 
       116   example: read entries from a SQL database (requires overriding
       117   get_request() to return a table entry from the database).
       118   entry is processed by a RequestHandlerClass.
       119 
       120 """
       121 
       122 # Author of the BaseServer patch: Luke Kenneth Casson Leighton
       123 
       124 # XXX Warning!
       125 # There is a test suite for this module, but it cannot be run by the
       126 # standard regression test.
       127 # To run it manually, run Lib/test/test_socketserver.py.
       128 
       129 __version__ = "0.4"
       130 
       131 
       132 import socket
       133 import select
       134 import sys
       135 import os
       136 import errno
       137 try:
       138     import threading
       139 except ImportError:
       140     import dummy_threading as threading
       141 
       142 __all__ = ["TCPServer","UDPServer","ForkingUDPServer","ForkingTCPServer",
       143            "ThreadingUDPServer","ThreadingTCPServer","BaseRequestHandler",
       144            "StreamRequestHandler","DatagramRequestHandler",
       145            "ThreadingMixIn", "ForkingMixIn"]
       146 if hasattr(socket, "AF_UNIX"):
       147     __all__.extend(["UnixStreamServer","UnixDatagramServer",
       148                     "ThreadingUnixStreamServer",
       149                     "ThreadingUnixDatagramServer"])
       150 
       151 def _eintr_retry(func, *args):
       152     """restart a system call interrupted by EINTR"""
       153     while True:
       154         try:
       155             return func(*args)
       156         except (OSError, select.error) as e:
       157             if e.args[0] != errno.EINTR:
       158                 raise
       159 
       160 class BaseServer:
       161 
       162     """Base class for server classes.
       163 
       164     Methods for the caller:
       165 
       166     - __init__(server_address, RequestHandlerClass)
       167     - serve_forever(poll_interval=0.5)
       168     - shutdown()
       169     - handle_request()  # if you do not use serve_forever()
       170     - fileno() -> int   # for select()
       171 
       172     Methods that may be overridden:
       173 
       174     - server_bind()
       175     - server_activate()
       176     - get_request() -> request, client_address
       177     - handle_timeout()
       178     - verify_request(request, client_address)
       179     - server_close()
       180     - process_request(request, client_address)
       181     - shutdown_request(request)
       182     - close_request(request)
       183     - handle_error()
       184 
       185     Methods for derived classes:
       186 
       187     - finish_request(request, client_address)
       188 
       189     Class variables that may be overridden by derived classes or
       190     instances:
       191 
       192     - timeout
       193     - address_family
       194     - socket_type
       195     - allow_reuse_address
       196 
       197     Instance variables:
       198 
       199     - RequestHandlerClass
       200     - socket
       201 
       202     """
       203 
       204     timeout = None
       205 
       206     def __init__(self, server_address, RequestHandlerClass):
       207         """Constructor.  May be extended, do not override."""
       208         self.server_address = server_address
       209         self.RequestHandlerClass = RequestHandlerClass
       210         self.__is_shut_down = threading.Event()
       211         self.__shutdown_request = False
       212 
       213     def server_activate(self):
       214         """Called by constructor to activate the server.
       215 
       216         May be overridden.
       217 
       218         """
       219         pass
       220 
       221     def serve_forever(self, poll_interval=0.5):
       222         """Handle one request at a time until shutdown.
       223 
       224         Polls for shutdown every poll_interval seconds. Ignores
       225         self.timeout. If you need to do periodic tasks, do them in
       226         another thread.
       227         """
       228         self.__is_shut_down.clear()
       229         try:
       230             while not self.__shutdown_request:
       231                 # XXX: Consider using another file descriptor or
       232                 # connecting to the socket to wake this up instead of
       233                 # polling. Polling reduces our responsiveness to a
       234                 # shutdown request and wastes cpu at all other times.
       235                 r, w, e = _eintr_retry(select.select, [self], [], [],
       236                                        poll_interval)
       237                 if self in r:
       238                     self._handle_request_noblock()
       239         finally:
       240             self.__shutdown_request = False
       241             self.__is_shut_down.set()
       242 
       243     def shutdown(self):
       244         """Stops the serve_forever loop.
       245 
       246         Blocks until the loop has finished. This must be called while
       247         serve_forever() is running in another thread, or it will
       248         deadlock.
       249         """
       250         self.__shutdown_request = True
       251         self.__is_shut_down.wait()
       252 
       253     # The distinction between handling, getting, processing and
       254     # finishing a request is fairly arbitrary.  Remember:
       255     #
       256     # - handle_request() is the top-level call.  It calls
       257     #   select, get_request(), verify_request() and process_request()
       258     # - get_request() is different for stream or datagram sockets
       259     # - process_request() is the place that may fork a new process
       260     #   or create a new thread to finish the request
       261     # - finish_request() instantiates the request handler class;
       262     #   this constructor will handle the request all by itself
       263 
       264     def handle_request(self):
       265         """Handle one request, possibly blocking.
       266 
       267         Respects self.timeout.
       268         """
       269         # Support people who used socket.settimeout() to escape
       270         # handle_request before self.timeout was available.
       271         timeout = self.socket.gettimeout()
       272         if timeout is None:
       273             timeout = self.timeout
       274         elif self.timeout is not None:
       275             timeout = min(timeout, self.timeout)
       276         fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
       277         if not fd_sets[0]:
       278             self.handle_timeout()
       279             return
       280         self._handle_request_noblock()
       281 
       282     def _handle_request_noblock(self):
       283         """Handle one request, without blocking.
       284 
       285         I assume that select.select has returned that the socket is
       286         readable before this function was called, so there should be
       287         no risk of blocking in get_request().
       288         """
       289         try:
       290             request, client_address = self.get_request()
       291         except socket.error:
       292             return
       293         if self.verify_request(request, client_address):
       294             try:
       295                 self.process_request(request, client_address)
       296             except:
       297                 self.handle_error(request, client_address)
       298                 self.shutdown_request(request)
       299 
       300     def handle_timeout(self):
       301         """Called if no new request arrives within self.timeout.
       302 
       303         Overridden by ForkingMixIn.
       304         """
       305         pass
       306 
       307     def verify_request(self, request, client_address):
       308         """Verify the request.  May be overridden.
       309 
       310         Return True if we should proceed with this request.
       311 
       312         """
       313         return True
       314 
       315     def process_request(self, request, client_address):
       316         """Call finish_request.
       317 
       318         Overridden by ForkingMixIn and ThreadingMixIn.
       319 
       320         """
       321         self.finish_request(request, client_address)
       322         self.shutdown_request(request)
       323 
       324     def server_close(self):
       325         """Called to clean-up the server.
       326 
       327         May be overridden.
       328 
       329         """
       330         pass
       331 
       332     def finish_request(self, request, client_address):
       333         """Finish one request by instantiating RequestHandlerClass."""
       334         self.RequestHandlerClass(request, client_address, self)
       335 
       336     def shutdown_request(self, request):
       337         """Called to shutdown and close an individual request."""
       338         self.close_request(request)
       339 
       340     def close_request(self, request):
       341         """Called to clean up an individual request."""
       342         pass
       343 
       344     def handle_error(self, request, client_address):
       345         """Handle an error gracefully.  May be overridden.
       346 
       347         The default is to print a traceback and continue.
       348 
       349         """
       350         print '-'*40
       351         print 'Exception happened during processing of request from',
       352         print client_address
       353         import traceback
       354         traceback.print_exc() # XXX But this goes to stderr!
       355         print '-'*40
       356 
       357 
       358 class TCPServer(BaseServer):
       359 
       360     """Base class for various socket-based server classes.
       361 
       362     Defaults to synchronous IP stream (i.e., TCP).
       363 
       364     Methods for the caller:
       365 
       366     - __init__(server_address, RequestHandlerClass, bind_and_activate=True)
       367     - serve_forever(poll_interval=0.5)
       368     - shutdown()
       369     - handle_request()  # if you don't use serve_forever()
       370     - fileno() -> int   # for select()
       371 
       372     Methods that may be overridden:
       373 
       374     - server_bind()
       375     - server_activate()
       376     - get_request() -> request, client_address
       377     - handle_timeout()
       378     - verify_request(request, client_address)
       379     - process_request(request, client_address)
       380     - shutdown_request(request)
       381     - close_request(request)
       382     - handle_error()
       383 
       384     Methods for derived classes:
       385 
       386     - finish_request(request, client_address)
       387 
       388     Class variables that may be overridden by derived classes or
       389     instances:
       390 
       391     - timeout
       392     - address_family
       393     - socket_type
       394     - request_queue_size (only for stream sockets)
       395     - allow_reuse_address
       396 
       397     Instance variables:
       398 
       399     - server_address
       400     - RequestHandlerClass
       401     - socket
       402 
       403     """
       404 
       405     address_family = socket.AF_INET
       406 
       407     socket_type = socket.SOCK_STREAM
       408 
       409     request_queue_size = 5
       410 
       411     allow_reuse_address = False
       412 
       413     def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
       414         """Constructor.  May be extended, do not override."""
       415         BaseServer.__init__(self, server_address, RequestHandlerClass)
       416         self.socket = socket.socket(self.address_family,
       417                                     self.socket_type)
       418         if bind_and_activate:
       419             self.server_bind()
       420             self.server_activate()
       421 
       422     def server_bind(self):
       423         """Called by constructor to bind the socket.
       424 
       425         May be overridden.
       426 
       427         """
       428         if self.allow_reuse_address:
       429             self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
       430         self.socket.bind(self.server_address)
       431         self.server_address = self.socket.getsockname()
       432 
       433     def server_activate(self):
       434         """Called by constructor to activate the server.
       435 
       436         May be overridden.
       437 
       438         """
       439         self.socket.listen(self.request_queue_size)
       440 
       441     def server_close(self):
       442         """Called to clean-up the server.
       443 
       444         May be overridden.
       445 
       446         """
       447         self.socket.close()
       448 
       449     def fileno(self):
       450         """Return socket file number.
       451 
       452         Interface required by select().
       453 
       454         """
       455         return self.socket.fileno()
       456 
       457     def get_request(self):
       458         """Get the request and client address from the socket.
       459 
       460         May be overridden.
       461 
       462         """
       463         return self.socket.accept()
       464 
       465     def shutdown_request(self, request):
       466         """Called to shutdown and close an individual request."""
       467         try:
       468             #explicitly shutdown.  socket.close() merely releases
       469             #the socket and waits for GC to perform the actual close.
       470             request.shutdown(socket.SHUT_WR)
       471         except socket.error:
       472             pass #some platforms may raise ENOTCONN here
       473         self.close_request(request)
       474 
       475     def close_request(self, request):
       476         """Called to clean up an individual request."""
       477         request.close()
       478 
       479 
       480 class UDPServer(TCPServer):
       481 
       482     """UDP server class."""
       483 
       484     allow_reuse_address = False
       485 
       486     socket_type = socket.SOCK_DGRAM
       487 
       488     max_packet_size = 8192
       489 
       490     def get_request(self):
       491         data, client_addr = self.socket.recvfrom(self.max_packet_size)
       492         return (data, self.socket), client_addr
       493 
       494     def server_activate(self):
       495         # No need to call listen() for UDP.
       496         pass
       497 
       498     def shutdown_request(self, request):
       499         # No need to shutdown anything.
       500         self.close_request(request)
       501 
       502     def close_request(self, request):
       503         # No need to close anything.
       504         pass
       505 
       506 class ForkingMixIn:
       507 
       508     """Mix-in class to handle each request in a new process."""
       509 
       510     timeout = 300
       511     active_children = None
       512     max_children = 40
       513 
       514     def collect_children(self):
       515         """Internal routine to wait for children that have exited."""
       516         if self.active_children is None: return
       517         while len(self.active_children) >= self.max_children:
       518             # XXX: This will wait for any child process, not just ones
       519             # spawned by this library. This could confuse other
       520             # libraries that expect to be able to wait for their own
       521             # children.
       522             try:
       523                 pid, status = os.waitpid(0, 0)
       524             except os.error:
       525                 pid = None
       526             if pid not in self.active_children: continue
       527             self.active_children.remove(pid)
       528 
       529         # XXX: This loop runs more system calls than it ought
       530         # to. There should be a way to put the active_children into a
       531         # process group and then use os.waitpid(-pgid) to wait for any
       532         # of that set, but I couldn't find a way to allocate pgids
       533         # that couldn't collide.
       534         for child in self.active_children:
       535             try:
       536                 pid, status = os.waitpid(child, os.WNOHANG)
       537             except os.error:
       538                 pid = None
       539             if not pid: continue
       540             try:
       541                 self.active_children.remove(pid)
       542             except ValueError, e:
       543                 raise ValueError('%s. x=%d and list=%r' % (e.message, pid,
       544                                                            self.active_children))
       545 
       546     def handle_timeout(self):
       547         """Wait for zombies after self.timeout seconds of inactivity.
       548 
       549         May be extended, do not override.
       550         """
       551         self.collect_children()
       552 
       553     def process_request(self, request, client_address):
       554         """Fork a new subprocess to process the request."""
       555         self.collect_children()
       556         pid = os.fork()
       557         if pid:
       558             # Parent process
       559             if self.active_children is None:
       560                 self.active_children = []
       561             self.active_children.append(pid)
       562             self.close_request(request) #close handle in parent process
       563             return
       564         else:
       565             # Child process.
       566             # This must never return, hence os._exit()!
       567             try:
       568                 self.finish_request(request, client_address)
       569                 self.shutdown_request(request)
       570                 os._exit(0)
       571             except:
       572                 try:
       573                     self.handle_error(request, client_address)
       574                     self.shutdown_request(request)
       575                 finally:
       576                     os._exit(1)
       577 
       578 
       579 class ThreadingMixIn:
       580     """Mix-in class to handle each request in a new thread."""
       581 
       582     # Decides how threads will act upon termination of the
       583     # main process
       584     daemon_threads = False
       585 
       586     def process_request_thread(self, request, client_address):
       587         """Same as in BaseServer but as a thread.
       588 
       589         In addition, exception handling is done here.
       590 
       591         """
       592         try:
       593             self.finish_request(request, client_address)
       594             self.shutdown_request(request)
       595         except:
       596             self.handle_error(request, client_address)
       597             self.shutdown_request(request)
       598 
       599     def process_request(self, request, client_address):
       600         """Start a new thread to process the request."""
       601         t = threading.Thread(target = self.process_request_thread,
       602                              args = (request, client_address))
       603         t.daemon = self.daemon_threads
       604         t.start()
       605 
       606 
       607 class ForkingUDPServer(ForkingMixIn, UDPServer): pass
       608 class ForkingTCPServer(ForkingMixIn, TCPServer): pass
       609 
       610 class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass
       611 class ThreadingTCPServer(ThreadingMixIn, TCPServer): pass
       612 
       613 if hasattr(socket, 'AF_UNIX'):
       614 
       615     class UnixStreamServer(TCPServer):
       616         address_family = socket.AF_UNIX
       617 
       618     class UnixDatagramServer(UDPServer):
       619         address_family = socket.AF_UNIX
       620 
       621     class ThreadingUnixStreamServer(ThreadingMixIn, UnixStreamServer): pass
       622 
       623     class ThreadingUnixDatagramServer(ThreadingMixIn, UnixDatagramServer): pass
       624 
       625 class BaseRequestHandler:
       626 
       627     """Base class for request handler classes.
       628 
       629     This class is instantiated for each request to be handled.  The
       630     constructor sets the instance variables request, client_address
       631     and server, and then calls the handle() method.  To implement a
       632     specific service, all you need to do is to derive a class which
       633     defines a handle() method.
       634 
       635     The handle() method can find the request as self.request, the
       636     client address as self.client_address, and the server (in case it
       637     needs access to per-server information) as self.server.  Since a
       638     separate instance is created for each request, the handle() method
       639     can define arbitrary other instance variariables.
       640 
       641     """
       642 
       643     def __init__(self, request, client_address, server):
       644         self.request = request
       645         self.client_address = client_address
       646         self.server = server
       647         self.setup()
       648         try:
       649             self.handle()
       650         finally:
       651             self.finish()
       652 
       653     def setup(self):
       654         pass
       655 
       656     def handle(self):
       657         pass
       658 
       659     def finish(self):
       660         pass
       661 
       662 
       663 # The following two classes make it possible to use the same service
       664 # class for stream or datagram servers.
       665 # Each class sets up these instance variables:
       666 # - rfile: a file object from which receives the request is read
       667 # - wfile: a file object to which the reply is written
       668 # When the handle() method returns, wfile is flushed properly
       669 
       670 
       671 class StreamRequestHandler(BaseRequestHandler):
       672 
       673     """Define self.rfile and self.wfile for stream sockets."""
       674 
       675     # Default buffer sizes for rfile, wfile.
       676     # We default rfile to buffered because otherwise it could be
       677     # really slow for large data (a getc() call per byte); we make
       678     # wfile unbuffered because (a) often after a write() we want to
       679     # read and we need to flush the line; (b) big writes to unbuffered
       680     # files are typically optimized by stdio even when big reads
       681     # aren't.
       682     rbufsize = -1
       683     wbufsize = 0
       684 
       685     # A timeout to apply to the request socket, if not None.
       686     timeout = None
       687 
       688     # Disable nagle algorithm for this socket, if True.
       689     # Use only when wbufsize != 0, to avoid small packets.
       690     disable_nagle_algorithm = False
       691 
       692     def setup(self):
       693         self.connection = self.request
       694         if self.timeout is not None:
       695             self.connection.settimeout(self.timeout)
       696         if self.disable_nagle_algorithm:
       697             self.connection.setsockopt(socket.IPPROTO_TCP,
       698                                        socket.TCP_NODELAY, True)
       699         self.rfile = self.connection.makefile('rb', self.rbufsize)
       700         self.wfile = self.connection.makefile('wb', self.wbufsize)
       701 
       702     def finish(self):
       703         if not self.wfile.closed:
       704             self.wfile.flush()
       705         self.wfile.close()
       706         self.rfile.close()
       707 
       708 
       709 class DatagramRequestHandler(BaseRequestHandler):
       710 
       711     # XXX Regrettably, I cannot get this working on Linux;
       712     # s.recvfrom() doesn't return a meaningful client address.
       713 
       714     """Define self.rfile and self.wfile for datagram sockets."""
       715 
       716     def setup(self):
       717         try:
       718             from cStringIO import StringIO
       719         except ImportError:
       720             from StringIO import StringIO
       721         self.packet, self.socket = self.request
       722         self.rfile = StringIO(self.packet)
       723         self.wfile = StringIO()
       724 
       725     def finish(self):
       726         self.socket.sendto(self.wfile.getvalue(), self.client_address)
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  • 原文地址:https://www.cnblogs.com/hzhida/p/2646018.html
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