Source code for boltons.socketutils

# -*- coding: utf-8 -*-
"""At its heart, Python can be viewed as an extension of the C
programming language. Springing from the most popular systems
programming language has made Python itself a great language for
systems programming. One key to success in this domain is Python's
very serviceable :mod:`socket` module and its :class:`socket.socket`
type.

The ``socketutils`` module provides natural next steps to the ``socket``
builtin: straightforward, tested building blocks for higher-level
protocols.

The :class:`BufferedSocket` wraps an ordinary socket, providing a
layer of intuitive buffering for both sending and receiving. This
facilitates parsing messages from streams, i.e., all sockets with type
``SOCK_STREAM``. The BufferedSocket enables receiving until the next
relevant token, up to a certain size, or until the connection is
closed. For all of these, it provides consistent APIs to size
limiting, as well as timeouts that are compatible with multiple
concurrency paradigms. Use it to parse the next one-off text or binary
socket protocol you encounter.

This module also provides the :class:`NetstringSocket`, a pure-Python
implementation of `the Netstring protocol`_, built on top of the
:class:`BufferedSocket`, serving as a ready-made, production-grade example.

Special thanks to `Kurt Rose`_ for his original authorship and all his
contributions on this module. Also thanks to `Daniel J. Bernstein`_, the
original author of `Netstring`_.

.. _the Netstring protocol: https://en.wikipedia.org/wiki/Netstring
.. _Kurt Rose: https://github.com/doublereedkurt
.. _Daniel J. Bernstein: https://cr.yp.to/
.. _Netstring: https://cr.yp.to/proto/netstrings.txt

"""

import time
import socket

try:
    from threading import RLock
except Exception:
    class RLock(object):
        'Dummy reentrant lock for builds without threads'
        def __enter__(self):
            pass

        def __exit__(self, exctype, excinst, exctb):
            pass


try:
    from typeutils import make_sentinel
    _UNSET = make_sentinel(var_name='_UNSET')
except ImportError:
    _UNSET = object()


DEFAULT_TIMEOUT = 10  # 10 seconds
DEFAULT_MAXSIZE = 32 * 1024  # 32kb
_RECV_LARGE_MAXSIZE = 1024 ** 5  # 1PB


[docs]class BufferedSocket(object): """Mainly provides recv_until and recv_size. recv, send, sendall, and peek all function as similarly as possible to the built-in socket API. This type has been tested against both the built-in socket type as well as those from gevent and eventlet. It also features support for sockets with timeouts set to 0 (aka nonblocking), provided the caller is prepared to handle the EWOULDBLOCK exceptions. Args: sock (socket): The connected socket to be wrapped. timeout (float): The default timeout for sends and recvs, in seconds. Set to ``None`` for no timeout, and 0 for nonblocking. Defaults to *sock*'s own timeout if already set, and 10 seconds otherwise. maxsize (int): The default maximum number of bytes to be received into the buffer before it is considered full and raises an exception. Defaults to 32 kilobytes. recvsize (int): The number of bytes to recv for every lower-level :meth:`socket.recv` call. Defaults to *maxsize*. *timeout* and *maxsize* can both be overridden on individual socket operations. All ``recv`` methods return bytestrings (:class:`bytes`) and can raise :exc:`socket.error`. :exc:`Timeout`, :exc:`ConnectionClosed`, and :exc:`MessageTooLong` all inherit from :exc:`socket.error` and exist to provide better error messages. Received bytes are always buffered, even if an exception is raised. Use :meth:`BufferedSocket.getrecvbuffer` to retrieve partial recvs. BufferedSocket does not replace the built-in socket by any means. While the overlapping parts of the API are kept parallel to the built-in :class:`socket.socket`, BufferedSocket does not inherit from socket, and most socket functionality is only available on the underlying socket. :meth:`socket.getpeername`, :meth:`socket.getsockname`, :meth:`socket.fileno`, and others are only available on the underlying socket that is wrapped. Use the ``BufferedSocket.sock`` attribute to access it. See the examples for more information on how to use BufferedSockets with built-in sockets. The BufferedSocket is threadsafe, but consider the semantics of your protocol before accessing a single socket from multiple threads. Similarly, once the BufferedSocket is constructed, avoid using the underlying socket directly. Only use it for operations unrelated to messages, e.g., :meth:`socket.getpeername`. """ def __init__(self, sock, timeout=_UNSET, maxsize=DEFAULT_MAXSIZE, recvsize=_UNSET): self.sock = sock self.rbuf = b'' self.sbuf = [] self.maxsize = int(maxsize) if timeout is _UNSET: if self.sock.gettimeout() is None: self.timeout = DEFAULT_TIMEOUT else: self.timeout = self.sock.gettimeout() else: if timeout is None: self.timeout = timeout else: self.timeout = float(timeout) if recvsize is _UNSET: self._recvsize = self.maxsize else: self._recvsize = int(recvsize) self._send_lock = RLock() self._recv_lock = RLock()
[docs] def settimeout(self, timeout): "Set the default *timeout* for future operations, in seconds." self.timeout = timeout
def gettimeout(self): return self.timeout def setblocking(self, blocking): self.timeout = None if blocking else 0.0
[docs] def setmaxsize(self, maxsize): """Set the default maximum buffer size *maxsize* for future operations, in bytes. Does not truncate the current buffer. """ self.maxsize = maxsize
[docs] def getrecvbuffer(self): "Returns the receive buffer bytestring (rbuf)." with self._recv_lock: return self.rbuf
[docs] def getsendbuffer(self): "Returns a copy of the send buffer list." with self._send_lock: return b''.join(self.sbuf)
[docs] def recv(self, size, flags=0, timeout=_UNSET): """Returns **up to** *size* bytes, using the internal buffer before performing a single :meth:`socket.recv` operation. Args: size (int): The maximum number of bytes to receive. flags (int): Kept for API compatibility with sockets. Only the default, ``0``, is valid. timeout (float): The timeout for this operation. Can be ``0`` for nonblocking and ``None`` for no timeout. Defaults to the value set in the constructor of BufferedSocket. If the operation does not complete in *timeout* seconds, a :exc:`Timeout` is raised. Much like the built-in :class:`socket.socket`, if this method returns an empty string, then the socket is closed and recv buffer is empty. Further calls to recv will raise :exc:`socket.error`. """ with self._recv_lock: if timeout is _UNSET: timeout = self.timeout if flags: raise ValueError("non-zero flags not supported: %r" % flags) if len(self.rbuf) >= size: data, self.rbuf = self.rbuf[:size], self.rbuf[size:] return data if self.rbuf: ret, self.rbuf = self.rbuf, b'' return ret self.sock.settimeout(timeout) try: data = self.sock.recv(self._recvsize) except socket.timeout: raise Timeout(timeout) # check the rbuf attr for more if len(data) > size: data, self.rbuf = data[:size], data[size:] return data
[docs] def peek(self, size, timeout=_UNSET): """Returns *size* bytes from the socket and/or internal buffer. Bytes are retained in BufferedSocket's internal recv buffer. To only see bytes in the recv buffer, use :meth:`getrecvbuffer`. Args: size (int): The exact number of bytes to peek at timeout (float): The timeout for this operation. Can be 0 for nonblocking and None for no timeout. Defaults to the value set in the constructor of BufferedSocket. If the appropriate number of bytes cannot be fetched from the buffer and socket before *timeout* expires, then a :exc:`Timeout` will be raised. If the connection is closed, a :exc:`ConnectionClosed` will be raised. """ with self._recv_lock: if len(self.rbuf) >= size: return self.rbuf[:size] data = self.recv_size(size, timeout=timeout) self.rbuf = data + self.rbuf return data
[docs] def recv_close(self, timeout=_UNSET, maxsize=_UNSET): """Receive until the connection is closed, up to *maxsize* bytes. If more than *maxsize* bytes are received, raises :exc:`MessageTooLong`. """ # recv_close works by using recv_size to request maxsize data, # and ignoring ConnectionClose, returning and clearing the # internal buffer instead. It raises an exception if # ConnectionClosed isn't raised. with self._recv_lock: if maxsize is _UNSET: maxsize = self.maxsize if maxsize is None: maxsize = _RECV_LARGE_MAXSIZE try: recvd = self.recv_size(maxsize + 1, timeout) except ConnectionClosed: ret, self.rbuf = self.rbuf, b'' else: # put extra received bytes (now in rbuf) after recvd self.rbuf = recvd + self.rbuf size_read = min(maxsize, len(self.rbuf)) raise MessageTooLong(size_read) # check receive buffer return ret
[docs] def recv_until(self, delimiter, timeout=_UNSET, maxsize=_UNSET, with_delimiter=False): """Receive until *delimiter* is found, *maxsize* bytes have been read, or *timeout* is exceeded. Args: delimiter (bytes): One or more bytes to be searched for in the socket stream. timeout (float): The timeout for this operation. Can be 0 for nonblocking and None for no timeout. Defaults to the value set in the constructor of BufferedSocket. maxsize (int): The maximum size for the internal buffer. Defaults to the value set in the constructor. with_delimiter (bool): Whether or not to include the delimiter in the output. ``False`` by default, but ``True`` is useful in cases where one is simply forwarding the messages. ``recv_until`` will raise the following exceptions: * :exc:`Timeout` if more than *timeout* seconds expire. * :exc:`ConnectionClosed` if the underlying socket is closed by the sending end. * :exc:`MessageTooLong` if the delimiter is not found in the first *maxsize* bytes. * :exc:`socket.error` if operating in nonblocking mode (*timeout* equal to 0), or if some unexpected socket error occurs, such as operating on a closed socket. """ with self._recv_lock: if maxsize is _UNSET: maxsize = self.maxsize if maxsize is None: maxsize = _RECV_LARGE_MAXSIZE if timeout is _UNSET: timeout = self.timeout len_delimiter = len(delimiter) sock = self.sock recvd = bytearray(self.rbuf) start = time.time() find_offset_start = 0 # becomes a negative index below if not timeout: # covers None (no timeout) and 0 (nonblocking) sock.settimeout(timeout) try: while 1: offset = recvd.find(delimiter, find_offset_start, maxsize) if offset != -1: # str.find returns -1 when no match found if with_delimiter: # include delimiter in return offset += len_delimiter rbuf_offset = offset else: rbuf_offset = offset + len_delimiter break elif len(recvd) > maxsize: raise MessageTooLong(maxsize, delimiter) # see rbuf if timeout: cur_timeout = timeout - (time.time() - start) if cur_timeout <= 0.0: raise socket.timeout() sock.settimeout(cur_timeout) nxt = sock.recv(self._recvsize) if not nxt: args = (len(recvd), delimiter) msg = ('connection closed after reading %s bytes' ' without finding symbol: %r' % args) raise ConnectionClosed(msg) # check the recv buffer recvd.extend(nxt) find_offset_start = -len(nxt) - len_delimiter + 1 except socket.timeout: self.rbuf = bytes(recvd) msg = ('read %s bytes without finding delimiter: %r' % (len(recvd), delimiter)) raise Timeout(timeout, msg) # check the recv buffer except Exception: self.rbuf = bytes(recvd) raise val, self.rbuf = bytes(recvd[:offset]), bytes(recvd[rbuf_offset:]) return val
[docs] def recv_size(self, size, timeout=_UNSET): """Read off of the internal buffer, then off the socket, until *size* bytes have been read. Args: size (int): number of bytes to read before returning. timeout (float): The timeout for this operation. Can be 0 for nonblocking and None for no timeout. Defaults to the value set in the constructor of BufferedSocket. If the appropriate number of bytes cannot be fetched from the buffer and socket before *timeout* expires, then a :exc:`Timeout` will be raised. If the connection is closed, a :exc:`ConnectionClosed` will be raised. """ with self._recv_lock: if timeout is _UNSET: timeout = self.timeout chunks = [] total_bytes = 0 try: start = time.time() self.sock.settimeout(timeout) nxt = self.rbuf or self.sock.recv(self._recvsize) while nxt: total_bytes += len(nxt) if total_bytes >= size: break chunks.append(nxt) if timeout: cur_timeout = timeout - (time.time() - start) if cur_timeout <= 0.0: raise socket.timeout() self.sock.settimeout(cur_timeout) nxt = self.sock.recv(self._recvsize) else: msg = ('connection closed after reading %s of %s requested' ' bytes' % (total_bytes, size)) raise ConnectionClosed(msg) # check recv buffer except socket.timeout: self.rbuf = b''.join(chunks) msg = 'read %s of %s bytes' % (total_bytes, size) raise Timeout(timeout, msg) # check recv buffer except Exception: # received data is still buffered in the case of errors self.rbuf = b''.join(chunks) raise extra_bytes = total_bytes - size if extra_bytes: last, self.rbuf = nxt[:-extra_bytes], nxt[-extra_bytes:] else: last, self.rbuf = nxt, b'' chunks.append(last) return b''.join(chunks)
[docs] def send(self, data, flags=0, timeout=_UNSET): """Send the contents of the internal send buffer, as well as *data*, to the receiving end of the connection. Returns the total number of bytes sent. If no exception is raised, all of *data* was sent and the internal send buffer is empty. Args: data (bytes): The bytes to send. flags (int): Kept for API compatibility with sockets. Only the default 0 is valid. timeout (float): The timeout for this operation. Can be 0 for nonblocking and None for no timeout. Defaults to the value set in the constructor of BufferedSocket. Will raise :exc:`Timeout` if the send operation fails to complete before *timeout*. In the event of an exception, use :meth:`BufferedSocket.getsendbuffer` to see which data was unsent. """ with self._send_lock: if timeout is _UNSET: timeout = self.timeout if flags: raise ValueError("non-zero flags not supported") sbuf = self.sbuf sbuf.append(data) if len(sbuf) > 1: sbuf[:] = [b''.join([s for s in sbuf if s])] self.sock.settimeout(timeout) start, total_sent = time.time(), 0 try: while sbuf[0]: sent = self.sock.send(sbuf[0]) total_sent += sent sbuf[0] = sbuf[0][sent:] if timeout: cur_timeout = timeout - (time.time() - start) if cur_timeout <= 0.0: raise socket.timeout() self.sock.settimeout(cur_timeout) except socket.timeout: raise Timeout(timeout, '%s bytes unsent' % len(sbuf[0])) return total_sent
[docs] def sendall(self, data, flags=0, timeout=_UNSET): """A passthrough to :meth:`~BufferedSocket.send`, retained for parallelism to the :class:`socket.socket` API. """ return self.send(data, flags, timeout)
[docs] def flush(self): "Send the contents of the internal send buffer." with self._send_lock: self.send(b'') return
[docs] def buffer(self, data): "Buffer *data* bytes for the next send operation." with self._send_lock: self.sbuf.append(data) return
# # # # # # Passing through some socket basics # # #
[docs] def getsockname(self): """Convenience function to return the wrapped socket's own address. See :meth:`socket.getsockname` for more details. """ return self.sock.getsockname()
[docs] def getpeername(self): """Convenience function to return the remote address to which the wrapped socket is connected. See :meth:`socket.getpeername` for more details. """ return self.sock.getpeername()
[docs] def getsockopt(self, level, optname, buflen=None): """Convenience function passing through to the wrapped socket's :meth:`socket.getsockopt`. """ args = (level, optname) if buflen is not None: args += (buflen,) return self.sock.getsockopt(*args)
[docs] def setsockopt(self, level, optname, value): """Convenience function passing through to the wrapped socket's :meth:`socket.setsockopt`. """ return self.sock.setsockopt(level, optname, value)
@property def type(self): """A passthrough to the wrapped socket's type. Valid usages should only ever see :data:`socket.SOCK_STREAM`. """ return self.sock.type @property def family(self): """A passthrough to the wrapped socket's family. BufferedSocket supports all widely-used families, so this read-only attribute can be one of :data:`socket.AF_INET` for IP, :data:`socket.AF_INET6` for IPv6, and :data:`socket.AF_UNIX` for UDS. """ return self.sock.family @property def proto(self): """A passthrough to the wrapped socket's protocol. The ``proto`` attribute is very rarely used, so it's always 0, meaning "the default" protocol. Pretty much all the practical information is in :attr:`~BufferedSocket.type` and :attr:`~BufferedSocket.family`, so you can go back to never thinking about this. """ return self.sock.proto # # # # # # Now for some more advanced interpretations of the builtin socket # # #
[docs] def fileno(self): """Returns the file descriptor of the wrapped socket. -1 if it has been closed on this end. Note that this makes the BufferedSocket selectable, i.e., usable for operating system event loops without any external libraries. Keep in mind that the operating system cannot know about data in BufferedSocket's internal buffer. Exercise discipline with calling ``recv*`` functions. """ return self.sock.fileno()
[docs] def close(self): """Closes the wrapped socket, and empties the internal buffers. The send buffer is not flushed automatically, so if you have been calling :meth:`~BufferedSocket.buffer`, be sure to call :meth:`~BufferedSocket.flush` before calling this method. After calling this method, future socket operations will raise :exc:`socket.error`. """ with self._recv_lock: with self._send_lock: self.rbuf = b'' self.rbuf_unconsumed = self.rbuf self.sbuf[:] = [] self.sock.close() return
[docs] def shutdown(self, how): """Convenience method which passes through to the wrapped socket's :meth:`~socket.shutdown`. Semantics vary by platform, so no special internal handling is done with the buffers. This method exists to facilitate the most common usage, wherein a full ``shutdown`` is followed by a :meth:`~BufferedSocket.close`. Developers requiring more support, please open `an issue`_. .. _an issue: https://github.com/mahmoud/boltons/issues """ with self._recv_lock: with self._send_lock: self.sock.shutdown(how) return
# end BufferedSocket
[docs]class Error(socket.error): """A subclass of :exc:`socket.error` from which all other ``socketutils`` exceptions inherit. When using :class:`BufferedSocket` and other ``socketutils`` types, generally you want to catch one of the specific exception types below, or :exc:`socket.error`. """ pass
[docs]class ConnectionClosed(Error): """Raised when receiving and the connection is unexpectedly closed from the sending end. Raised from :class:`BufferedSocket`'s :meth:`~BufferedSocket.peek`, :meth:`~BufferedSocket.recv_until`, and :meth:`~BufferedSocket.recv_size`, and never from its :meth:`~BufferedSocket.recv` or :meth:`~BufferedSocket.recv_close`. """ pass
[docs]class MessageTooLong(Error): """Raised from :meth:`BufferedSocket.recv_until` and :meth:`BufferedSocket.recv_closed` when more than *maxsize* bytes are read without encountering the delimiter or a closed connection, respectively. """ def __init__(self, bytes_read=None, delimiter=None): msg = 'message exceeded maximum size' if bytes_read is not None: msg += '. %s bytes read' % (bytes_read,) if delimiter is not None: msg += '. Delimiter not found: %r' % (delimiter,) super(MessageTooLong, self).__init__(msg)
[docs]class Timeout(socket.timeout, Error): """Inheriting from :exc:`socket.timeout`, Timeout is used to indicate when a socket operation did not complete within the time specified. Raised from any of :class:`BufferedSocket`'s ``recv`` methods. """ def __init__(self, timeout, extra=""): msg = 'socket operation timed out' if timeout is not None: msg += ' after %sms.' % (timeout * 1000) if extra: msg += ' ' + extra super(Timeout, self).__init__(msg)
[docs]class NetstringSocket(object): """ Reads and writes using the netstring protocol. More info: https://en.wikipedia.org/wiki/Netstring Even more info: http://cr.yp.to/proto/netstrings.txt """ def __init__(self, sock, timeout=DEFAULT_TIMEOUT, maxsize=DEFAULT_MAXSIZE): self.bsock = BufferedSocket(sock) self.timeout = timeout self.maxsize = maxsize self._msgsize_maxsize = len(str(maxsize)) + 1 # len(str()) == log10 def fileno(self): return self.bsock.fileno() def settimeout(self, timeout): self.timeout = timeout def setmaxsize(self, maxsize): self.maxsize = maxsize self._msgsize_maxsize = self._calc_msgsize_maxsize(maxsize) def _calc_msgsize_maxsize(self, maxsize): return len(str(maxsize)) + 1 # len(str()) == log10 def read_ns(self, timeout=_UNSET, maxsize=_UNSET): if timeout is _UNSET: timeout = self.timeout if maxsize is _UNSET: maxsize = self.maxsize msgsize_maxsize = self._msgsize_maxsize else: msgsize_maxsize = self._calc_msgsize_maxsize(maxsize) size_prefix = self.bsock.recv_until(b':', timeout=timeout, maxsize=msgsize_maxsize) try: size = int(size_prefix) except ValueError: raise NetstringInvalidSize('netstring message size must be valid' ' integer, not %r' % size_prefix) if size > maxsize: raise NetstringMessageTooLong(size, maxsize) payload = self.bsock.recv_size(size) if self.bsock.recv(1) != b',': raise NetstringProtocolError("expected trailing ',' after message") return payload def write_ns(self, payload): size = len(payload) if size > self.maxsize: raise NetstringMessageTooLong(size, self.maxsize) data = str(size).encode('ascii') + b':' + payload + b',' self.bsock.send(data)
[docs]class NetstringProtocolError(Error): "Base class for all of socketutils' Netstring exception types." pass
[docs]class NetstringInvalidSize(NetstringProtocolError): """NetstringInvalidSize is raised when the ``:``-delimited size prefix of the message does not contain a valid integer. Message showing valid size:: 5:hello, Here the ``5`` is the size. Anything in this prefix position that is not parsable as a Python integer (i.e., :class:`int`) will raise this exception. """ def __init__(self, msg): super(NetstringInvalidSize, self).__init__(msg)
[docs]class NetstringMessageTooLong(NetstringProtocolError): """NetstringMessageTooLong is raised when the size prefix contains a valid integer, but that integer is larger than the :class:`NetstringSocket`'s configured *maxsize*. When this exception is raised, it's recommended to simply close the connection instead of trying to recover. """ def __init__(self, size, maxsize): msg = ('netstring message length exceeds configured maxsize: %s > %s' % (size, maxsize)) super(NetstringMessageTooLong, self).__init__(msg)
""" attrs worth adding/passing through: properties: type, proto For its main functionality, BufferedSocket can wrap any object that has the following methods: - gettimeout() - settimeout() - recv(size) - send(data) The following methods are passed through: ... """ # TODO: buffered socket check socket.type == SOCK_STREAM? # TODO: make recv_until support taking a regex # TODO: including the delimiter in the recv_until return is not # necessary, as ConnectionClosed differentiates empty messages # from socket closes.