From 8733038b4de44a8cfb669420621597457eeef88a Mon Sep 17 00:00:00 2001 From: Stefan Israelsson Tampe Date: Thu, 6 Sep 2018 23:40:42 +0200 Subject: email policy works mm --- modules/language/python/module/socketserver.py | 795 +++++++++++++++++++++++++ 1 file changed, 795 insertions(+) create mode 100644 modules/language/python/module/socketserver.py (limited to 'modules/language/python/module/socketserver.py') diff --git a/modules/language/python/module/socketserver.py b/modules/language/python/module/socketserver.py new file mode 100644 index 0000000..516f718 --- /dev/null +++ b/modules/language/python/module/socketserver.py @@ -0,0 +1,795 @@ +module(socketserver) + +"""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 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 ForkingMixIn and ThreadingMixIn 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 request handler +subclasses 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 read 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 a selector 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 + +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 + + 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. + +""" + +# Author of the BaseServer patch: Luke Kenneth Casson Leighton + +__version__ = "0.4" + + +import socket +import selectors +import os +import errno +import sys +try: + import threading +except ImportError: + import dummy_threading as threading +from io import BufferedIOBase +from time import monotonic as time + +__all__ = ["BaseServer", "TCPServer", "UDPServer", + "ThreadingUDPServer", "ThreadingTCPServer", + "BaseRequestHandler", "StreamRequestHandler", + "DatagramRequestHandler", "ThreadingMixIn"] +if hasattr(os, "fork"): + __all__.extend(["ForkingUDPServer","ForkingTCPServer", "ForkingMixIn"]) +if hasattr(socket, "AF_UNIX"): + __all__.extend(["UnixStreamServer","UnixDatagramServer", + "ThreadingUnixStreamServer", + "ThreadingUnixDatagramServer"]) + +# poll/select have the advantage of not requiring any extra file descriptor, +# contrarily to epoll/kqueue (also, they require a single syscall). +if hasattr(selectors, 'PollSelector'): + _ServerSelector = selectors.PollSelector +else: + _ServerSelector = selectors.SelectSelector + + +class BaseServer: + + """Base class for server classes. + + Methods for the caller: + + - __init__(server_address, RequestHandlerClass) + - serve_forever(poll_interval=0.5) + - shutdown() + - handle_request() # if you do not use serve_forever() + - fileno() -> int # for selector + + Methods that may be overridden: + + - server_bind() + - server_activate() + - get_request() -> request, client_address + - handle_timeout() + - verify_request(request, client_address) + - server_close() + - process_request(request, client_address) + - shutdown_request(request) + - close_request(request) + - service_actions() + - handle_error() + + Methods for derived classes: + + - finish_request(request, client_address) + + Class variables that may be overridden by derived classes or + instances: + + - timeout + - address_family + - socket_type + - allow_reuse_address + + Instance variables: + + - RequestHandlerClass + - socket + + """ + + timeout = None + + def __init__(self, server_address, RequestHandlerClass): + """Constructor. May be extended, do not override.""" + self.server_address = server_address + self.RequestHandlerClass = RequestHandlerClass + self.__is_shut_down = threading.Event() + self.__shutdown_request = False + + def server_activate(self): + """Called by constructor to activate the server. + + May be overridden. + + """ + pass + + def serve_forever(self, poll_interval=0.5): + """Handle one request at a time until shutdown. + + Polls for shutdown every poll_interval seconds. Ignores + self.timeout. If you need to do periodic tasks, do them in + another thread. + """ + self.__is_shut_down.clear() + try: + # XXX: Consider using another file descriptor or connecting to the + # socket to wake this up instead of polling. Polling reduces our + # responsiveness to a shutdown request and wastes cpu at all other + # times. + with _ServerSelector() as selector: + selector.register(self, selectors.EVENT_READ) + + while not self.__shutdown_request: + ready = selector.select(poll_interval) + if ready: + self._handle_request_noblock() + + self.service_actions() + finally: + self.__shutdown_request = False + self.__is_shut_down.set() + + def shutdown(self): + """Stops the serve_forever loop. + + Blocks until the loop has finished. This must be called while + serve_forever() is running in another thread, or it will + deadlock. + """ + self.__shutdown_request = True + self.__is_shut_down.wait() + + def service_actions(self): + """Called by the serve_forever() loop. + + May be overridden by a subclass / Mixin to implement any code that + needs to be run during the loop. + """ + pass + + # The distinction between handling, getting, processing and finishing a + # request is fairly arbitrary. Remember: + # + # - handle_request() is the top-level call. It calls selector.select(), + # get_request(), verify_request() and process_request() + # - get_request() is different for stream or datagram sockets + # - process_request() is the place that may fork a new process or create a + # new thread to finish the request + # - finish_request() instantiates the request handler class; this + # constructor will handle the request all by itself + + def handle_request(self): + """Handle one request, possibly blocking. + + Respects self.timeout. + """ + # Support people who used socket.settimeout() to escape + # handle_request before self.timeout was available. + timeout = self.socket.gettimeout() + if timeout is None: + timeout = self.timeout + elif self.timeout is not None: + timeout = min(timeout, self.timeout) + if timeout is not None: + deadline = time() + timeout + + # Wait until a request arrives or the timeout expires - the loop is + # necessary to accommodate early wakeups due to EINTR. + with _ServerSelector() as selector: + selector.register(self, selectors.EVENT_READ) + + while True: + ready = selector.select(timeout) + if ready: + return self._handle_request_noblock() + else: + if timeout is not None: + timeout = deadline - time() + if timeout < 0: + return self.handle_timeout() + + def _handle_request_noblock(self): + """Handle one request, without blocking. + + I assume that selector.select() has returned that the socket is + readable before this function was called, so there should be no risk of + blocking in get_request(). + """ + try: + request, client_address = self.get_request() + except OSError: + return + if self.verify_request(request, client_address): + try: + self.process_request(request, client_address) + except Exception: + self.handle_error(request, client_address) + self.shutdown_request(request) + except: + self.shutdown_request(request) + raise + else: + self.shutdown_request(request) + + def handle_timeout(self): + """Called if no new request arrives within self.timeout. + + Overridden by ForkingMixIn. + """ + pass + + 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.shutdown_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 shutdown_request(self, request): + """Called to shutdown and close an individual request.""" + self.close_request(request) + + 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, file=sys.stderr) + print('Exception happened during processing of request from', + client_address, file=sys.stderr) + import traceback + traceback.print_exc() + print('-'*40, file=sys.stderr) + + def __enter__(self): + return self + + def __exit__(self, *args): + self.server_close() + + +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, bind_and_activate=True) + - serve_forever(poll_interval=0.5) + - shutdown() + - handle_request() # if you don't use serve_forever() + - fileno() -> int # for selector + + Methods that may be overridden: + + - server_bind() + - server_activate() + - get_request() -> request, client_address + - handle_timeout() + - verify_request(request, client_address) + - process_request(request, client_address) + - shutdown_request(request) + - 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: + + - timeout + - 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, bind_and_activate=True): + """Constructor. May be extended, do not override.""" + BaseServer.__init__(self, server_address, RequestHandlerClass) + self.socket = socket.socket(self.address_family, + self.socket_type) + if bind_and_activate: + try: + self.server_bind() + self.server_activate() + except: + self.server_close() + raise + + 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) + self.server_address = self.socket.getsockname() + + 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 selector. + + """ + 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 shutdown_request(self, request): + """Called to shutdown and close an individual request.""" + try: + #explicitly shutdown. socket.close() merely releases + #the socket and waits for GC to perform the actual close. + request.shutdown(socket.SHUT_WR) + except OSError: + pass #some platforms may raise ENOTCONN here + self.close_request(request) + + 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): + # No need to call listen() for UDP. + pass + + def shutdown_request(self, request): + # No need to shutdown anything. + self.close_request(request) + + def close_request(self, request): + # No need to close anything. + pass + +if hasattr(os, "fork"): + class ForkingMixIn: + """Mix-in class to handle each request in a new process.""" + + timeout = 300 + active_children = None + max_children = 40 + + def collect_children(self): + """Internal routine to wait for children that have exited.""" + if self.active_children is None: + return + + # If we're above the max number of children, wait and reap them until + # we go back below threshold. Note that we use waitpid(-1) below to be + # able to collect children in size() syscalls instead + # of size(): the downside is that this might reap children + # which we didn't spawn, which is why we only resort to this when we're + # above max_children. + while len(self.active_children) >= self.max_children: + try: + pid, _ = os.waitpid(-1, 0) + self.active_children.discard(pid) + except ChildProcessError: + # we don't have any children, we're done + self.active_children.clear() + except OSError: + break + + # Now reap all defunct children. + for pid in self.active_children.copy(): + try: + pid, _ = os.waitpid(pid, os.WNOHANG) + # if the child hasn't exited yet, pid will be 0 and ignored by + # discard() below + self.active_children.discard(pid) + except ChildProcessError: + # someone else reaped it + self.active_children.discard(pid) + except OSError: + pass + + def handle_timeout(self): + """Wait for zombies after self.timeout seconds of inactivity. + + May be extended, do not override. + """ + self.collect_children() + + def service_actions(self): + """Collect the zombie child processes regularly in the ForkingMixIn. + + service_actions is called in the BaseServer's serve_forver loop. + """ + self.collect_children() + + def process_request(self, request, client_address): + """Fork a new subprocess to process the request.""" + pid = os.fork() + if pid: + # Parent process + if self.active_children is None: + self.active_children = set() + self.active_children.add(pid) + self.close_request(request) + return + else: + # Child process. + # This must never return, hence os._exit()! + status = 1 + try: + self.finish_request(request, client_address) + status = 0 + except Exception: + self.handle_error(request, client_address) + finally: + try: + self.shutdown_request(request) + finally: + os._exit(status) + + +class ThreadingMixIn: + """Mix-in class to handle each request in a new thread.""" + + # Decides how threads will act upon termination of the + # main process + 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) + except Exception: + self.handle_error(request, client_address) + finally: + self.shutdown_request(request) + + def process_request(self, request, client_address): + """Start a new thread to process the request.""" + t = threading.Thread(target = self.process_request_thread, + args = (request, client_address)) + t.daemon = self.daemon_threads + t.start() + + +if hasattr(os, "fork"): + 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 other arbitrary instance variables. + + """ + + def __init__(self, request, client_address, server): + self.request = request + self.client_address = client_address + self.server = server + self.setup() + try: + self.handle() + finally: + self.finish() + + def setup(self): + pass + + def handle(self): + pass + + def finish(self): + pass + + +# The following two classes make it possible to use the same service +# class for stream or datagram servers. +# Each class sets up these instance variables: +# - rfile: a file object from which receives the request is read +# - wfile: a file object to which the reply is written +# When the handle() method returns, wfile is flushed properly + + +class StreamRequestHandler(BaseRequestHandler): + + """Define self.rfile and self.wfile for stream sockets.""" + + # Default buffer sizes for rfile, wfile. + # We default rfile to buffered because otherwise it could be + # really slow for large data (a getc() call per byte); we make + # wfile unbuffered because (a) often after a write() we want to + # read and we need to flush the line; (b) big writes to unbuffered + # files are typically optimized by stdio even when big reads + # aren't. + rbufsize = -1 + wbufsize = 0 + + # A timeout to apply to the request socket, if not None. + timeout = None + + # Disable nagle algorithm for this socket, if True. + # Use only when wbufsize != 0, to avoid small packets. + disable_nagle_algorithm = False + + def setup(self): + self.connection = self.request + if self.timeout is not None: + self.connection.settimeout(self.timeout) + if self.disable_nagle_algorithm: + self.connection.setsockopt(socket.IPPROTO_TCP, + socket.TCP_NODELAY, True) + self.rfile = self.connection.makefile('rb', self.rbufsize) + if self.wbufsize == 0: + self.wfile = _SocketWriter(self.connection) + else: + self.wfile = self.connection.makefile('wb', self.wbufsize) + + def finish(self): + if not self.wfile.closed: + try: + self.wfile.flush() + except socket.error: + # A final socket error may have occurred here, such as + # the local error ECONNABORTED. + pass + self.wfile.close() + self.rfile.close() + +class _SocketWriter(BufferedIOBase): + """Simple writable BufferedIOBase implementation for a socket + + Does not hold data in a buffer, avoiding any need to call flush().""" + + def __init__(self, sock): + self._sock = sock + + def writable(self): + return True + + def write(self, b): + self._sock.sendall(b) + with memoryview(b) as view: + return view.nbytes + + def fileno(self): + return self._sock.fileno() + +class DatagramRequestHandler(BaseRequestHandler): + + """Define self.rfile and self.wfile for datagram sockets.""" + + def setup(self): + from io import BytesIO + self.packet, self.socket = self.request + self.rfile = BytesIO(self.packet) + self.wfile = BytesIO() + + def finish(self): + self.socket.sendto(self.wfile.getvalue(), self.client_address) -- cgit v1.2.3