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| from cassandra.connection import Connection, ConnectionShutdown | |
| import asyncio | |
| import logging | |
| import os | |
| import socket | |
| import ssl | |
| from threading import Lock, Thread, get_ident | |
| log = logging.getLogger(__name__) | |
| # This module uses ``yield from`` and ``@asyncio.coroutine`` over ``await`` and | |
| # ``async def`` for pre-Python-3.5 compatibility, so keep in mind that the | |
| # managed coroutines are generator-based, not native coroutines. See PEP 492: | |
| # https://www.python.org/dev/peps/pep-0492/#coroutine-objects | |
| try: | |
| asyncio.run_coroutine_threadsafe | |
| except AttributeError: | |
| raise ImportError( | |
| 'Cannot use asyncioreactor without access to ' | |
| 'asyncio.run_coroutine_threadsafe (added in 3.4.6 and 3.5.1)' | |
| ) | |
| class AsyncioTimer(object): | |
| """ | |
| An ``asyncioreactor``-specific Timer. Similar to :class:`.connection.Timer, | |
| but with a slightly different API due to limitations in the underlying | |
| ``call_later`` interface. Not meant to be used with a | |
| :class:`.connection.TimerManager`. | |
| """ | |
| def end(self): | |
| raise NotImplementedError('{} is not compatible with TimerManager and ' | |
| 'does not implement .end()') | |
| def __init__(self, timeout, callback, loop): | |
| delayed = self._call_delayed_coro(timeout=timeout, | |
| callback=callback) | |
| self._handle = asyncio.run_coroutine_threadsafe(delayed, loop=loop) | |
| async def _call_delayed_coro(timeout, callback): | |
| await asyncio.sleep(timeout) | |
| return callback() | |
| def __lt__(self, other): | |
| try: | |
| return self._handle < other._handle | |
| except AttributeError: | |
| raise NotImplemented | |
| def cancel(self): | |
| self._handle.cancel() | |
| def finish(self): | |
| # connection.Timer method not implemented here because we can't inspect | |
| # the Handle returned from call_later | |
| raise NotImplementedError('{} is not compatible with TimerManager and ' | |
| 'does not implement .finish()') | |
| class AsyncioConnection(Connection): | |
| """ | |
| An experimental implementation of :class:`.Connection` that uses the | |
| ``asyncio`` module in the Python standard library for its event loop. | |
| Note that it requires ``asyncio`` features that were only introduced in the | |
| 3.4 line in 3.4.6, and in the 3.5 line in 3.5.1. | |
| """ | |
| _loop = None | |
| _pid = os.getpid() | |
| _lock = Lock() | |
| _loop_thread = None | |
| _write_queue = None | |
| _write_queue_lock = None | |
| def __init__(self, *args, **kwargs): | |
| Connection.__init__(self, *args, **kwargs) | |
| self._connect_socket() | |
| self._socket.setblocking(0) | |
| self._write_queue = asyncio.Queue() | |
| self._write_queue_lock = asyncio.Lock() | |
| # see initialize_reactor -- loop is running in a separate thread, so we | |
| # have to use a threadsafe call | |
| self._read_watcher = asyncio.run_coroutine_threadsafe( | |
| self.handle_read(), loop=self._loop | |
| ) | |
| self._write_watcher = asyncio.run_coroutine_threadsafe( | |
| self.handle_write(), loop=self._loop | |
| ) | |
| self._send_options_message() | |
| def initialize_reactor(cls): | |
| with cls._lock: | |
| if cls._pid != os.getpid(): | |
| cls._loop = None | |
| if cls._loop is None: | |
| cls._loop = asyncio.new_event_loop() | |
| asyncio.set_event_loop(cls._loop) | |
| if not cls._loop_thread: | |
| # daemonize so the loop will be shut down on interpreter | |
| # shutdown | |
| cls._loop_thread = Thread(target=cls._loop.run_forever, | |
| daemon=True, name="asyncio_thread") | |
| cls._loop_thread.start() | |
| def create_timer(cls, timeout, callback): | |
| return AsyncioTimer(timeout, callback, loop=cls._loop) | |
| def close(self): | |
| with self.lock: | |
| if self.is_closed: | |
| return | |
| self.is_closed = True | |
| # close from the loop thread to avoid races when removing file | |
| # descriptors | |
| asyncio.run_coroutine_threadsafe( | |
| self._close(), loop=self._loop | |
| ) | |
| async def _close(self): | |
| log.debug("Closing connection (%s) to %s" % (id(self), self.endpoint)) | |
| if self._write_watcher: | |
| self._write_watcher.cancel() | |
| if self._read_watcher: | |
| self._read_watcher.cancel() | |
| if self._socket: | |
| self._loop.remove_writer(self._socket.fileno()) | |
| self._loop.remove_reader(self._socket.fileno()) | |
| self._socket.close() | |
| log.debug("Closed socket to %s" % (self.endpoint,)) | |
| if not self.is_defunct: | |
| self.error_all_requests( | |
| ConnectionShutdown("Connection to %s was closed" % self.endpoint)) | |
| # don't leave in-progress operations hanging | |
| self.connected_event.set() | |
| def push(self, data): | |
| buff_size = self.out_buffer_size | |
| if len(data) > buff_size: | |
| chunks = [] | |
| for i in range(0, len(data), buff_size): | |
| chunks.append(data[i:i + buff_size]) | |
| else: | |
| chunks = [data] | |
| if self._loop_thread.ident != get_ident(): | |
| asyncio.run_coroutine_threadsafe( | |
| self._push_msg(chunks), | |
| loop=self._loop | |
| ) | |
| else: | |
| # avoid races/hangs by just scheduling this, not using threadsafe | |
| self._loop.create_task(self._push_msg(chunks)) | |
| async def _push_msg(self, chunks): | |
| # This lock ensures all chunks of a message are sequential in the Queue | |
| with await self._write_queue_lock: | |
| for chunk in chunks: | |
| self._write_queue.put_nowait(chunk) | |
| async def handle_write(self): | |
| while True: | |
| try: | |
| next_msg = await self._write_queue.get() | |
| if next_msg: | |
| await self._loop.sock_sendall(self._socket, next_msg) | |
| except socket.error as err: | |
| log.debug("Exception in send for %s: %s", self, err) | |
| self.defunct(err) | |
| return | |
| except asyncio.CancelledError: | |
| return | |
| async def handle_read(self): | |
| while True: | |
| try: | |
| buf = await self._loop.sock_recv(self._socket, self.in_buffer_size) | |
| self._iobuf.write(buf) | |
| # sock_recv expects EWOULDBLOCK if socket provides no data, but | |
| # nonblocking ssl sockets raise these instead, so we handle them | |
| # ourselves by yielding to the event loop, where the socket will | |
| # get the reading/writing it "wants" before retrying | |
| except (ssl.SSLWantWriteError, ssl.SSLWantReadError): | |
| # Apparently the preferred way to yield to the event loop from within | |
| # a native coroutine based on https://github.com/python/asyncio/issues/284 | |
| await asyncio.sleep(0) | |
| continue | |
| except socket.error as err: | |
| log.debug("Exception during socket recv for %s: %s", | |
| self, err) | |
| self.defunct(err) | |
| return # leave the read loop | |
| except asyncio.CancelledError: | |
| return | |
| if buf and self._iobuf.tell(): | |
| self.process_io_buffer() | |
| else: | |
| log.debug("Connection %s closed by server", self) | |
| self.close() | |
| return | |