414 lines
12 KiB
Python
414 lines
12 KiB
Python
# Copyright 2013-2017 DataStax, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import atexit
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from collections import deque
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from functools import partial
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import logging
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import os
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import socket
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import sys
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from threading import Lock, Thread
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import time
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import weakref
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from six.moves import range
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try:
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from weakref import WeakSet
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except ImportError:
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from cassandra.util import WeakSet # noqa
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import asyncore
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try:
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import ssl
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except ImportError:
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ssl = None # NOQA
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from cassandra.connection import Connection, ConnectionShutdown, NONBLOCKING, Timer, TimerManager
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log = logging.getLogger(__name__)
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_dispatcher_map = {}
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def _cleanup(loop_weakref):
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try:
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loop = loop_weakref()
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except ReferenceError:
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return
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loop._cleanup()
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class _PipeWrapper(object):
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def __init__(self, fd):
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self.fd = fd
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def fileno(self):
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return self.fd
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def close(self):
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os.close(self.fd)
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def getsockopt(self, level, optname, buflen=None):
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# act like an unerrored socket for the asyncore error handling
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if level == socket.SOL_SOCKET and optname == socket.SO_ERROR and not buflen:
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return 0
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raise NotImplementedError()
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class _AsyncoreDispatcher(asyncore.dispatcher):
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def __init__(self, socket):
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asyncore.dispatcher.__init__(self, map=_dispatcher_map)
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# inject after to avoid base class validation
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self.set_socket(socket)
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self._notified = False
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def writable(self):
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return False
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def validate(self):
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assert not self._notified
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self.notify_loop()
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assert self._notified
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self.loop(0.1)
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assert not self._notified
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def loop(self, timeout):
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asyncore.loop(timeout=timeout, use_poll=True, map=_dispatcher_map, count=1)
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class _AsyncorePipeDispatcher(_AsyncoreDispatcher):
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def __init__(self):
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self.read_fd, self.write_fd = os.pipe()
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_AsyncoreDispatcher.__init__(self, _PipeWrapper(self.read_fd))
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def writable(self):
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return False
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def handle_read(self):
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while len(os.read(self.read_fd, 4096)) == 4096:
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pass
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self._notified = False
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def notify_loop(self):
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if not self._notified:
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self._notified = True
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os.write(self.write_fd, b'x')
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class _AsyncoreUDPDispatcher(_AsyncoreDispatcher):
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"""
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Experimental alternate dispatcher for avoiding busy wait in the asyncore loop. It is not used by default because
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it relies on local port binding.
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Port scanning is not implemented, so multiple clients on one host will collide. This address would need to be set per
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instance, or this could be specialized to scan until an address is found.
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To use::
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from cassandra.io.asyncorereactor import _AsyncoreUDPDispatcher, AsyncoreLoop
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AsyncoreLoop._loop_dispatch_class = _AsyncoreUDPDispatcher
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"""
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bind_address = ('localhost', 10000)
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def __init__(self):
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self._socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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self._socket.bind(self.bind_address)
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self._socket.setblocking(0)
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_AsyncoreDispatcher.__init__(self, self._socket)
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def handle_read(self):
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try:
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d = self._socket.recvfrom(1)
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while d and d[1]:
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d = self._socket.recvfrom(1)
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except socket.error as e:
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pass
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self._notified = False
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def notify_loop(self):
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if not self._notified:
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self._notified = True
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self._socket.sendto(b'', self.bind_address)
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def loop(self, timeout):
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asyncore.loop(timeout=timeout, use_poll=False, map=_dispatcher_map, count=1)
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class _BusyWaitDispatcher(object):
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max_write_latency = 0.001
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"""
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Timeout pushed down to asyncore select/poll. Dictates the amount of time it will sleep before coming back to check
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if anything is writable.
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"""
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def notify_loop(self):
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pass
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def loop(self, timeout):
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if not _dispatcher_map:
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time.sleep(0.005)
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count = timeout // self.max_write_latency
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asyncore.loop(timeout=self.max_write_latency, use_poll=True, map=_dispatcher_map, count=count)
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def validate(self):
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pass
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def close(self):
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pass
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class AsyncoreLoop(object):
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timer_resolution = 0.1 # used as the max interval to be in the io loop before returning to service timeouts
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_loop_dispatch_class = _AsyncorePipeDispatcher if os.name != 'nt' else _BusyWaitDispatcher
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def __init__(self):
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self._pid = os.getpid()
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self._loop_lock = Lock()
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self._started = False
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self._shutdown = False
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self._thread = None
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self._timers = TimerManager()
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try:
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dispatcher = self._loop_dispatch_class()
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dispatcher.validate()
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log.debug("Validated loop dispatch with %s", self._loop_dispatch_class)
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except Exception:
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log.exception("Failed validating loop dispatch with %s. Using busy wait execution instead.", self._loop_dispatch_class)
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dispatcher.close()
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dispatcher = _BusyWaitDispatcher()
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self._loop_dispatcher = dispatcher
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atexit.register(partial(_cleanup, weakref.ref(self)))
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def maybe_start(self):
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should_start = False
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did_acquire = False
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try:
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did_acquire = self._loop_lock.acquire(False)
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if did_acquire and not self._started:
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self._started = True
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should_start = True
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finally:
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if did_acquire:
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self._loop_lock.release()
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if should_start:
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self._thread = Thread(target=self._run_loop, name="cassandra_driver_event_loop")
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self._thread.daemon = True
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self._thread.start()
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def wake_loop(self):
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self._loop_dispatcher.notify_loop()
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def _run_loop(self):
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log.debug("Starting asyncore event loop")
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with self._loop_lock:
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while not self._shutdown:
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try:
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self._loop_dispatcher.loop(self.timer_resolution)
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self._timers.service_timeouts()
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except Exception:
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log.debug("Asyncore event loop stopped unexepectedly", exc_info=True)
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break
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self._started = False
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log.debug("Asyncore event loop ended")
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def add_timer(self, timer):
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self._timers.add_timer(timer)
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def _cleanup(self):
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global _dispatcher_map
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self._shutdown = True
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if not self._thread:
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return
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log.debug("Waiting for event loop thread to join...")
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self._thread.join(timeout=1.0)
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if self._thread.is_alive():
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log.warning(
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"Event loop thread could not be joined, so shutdown may not be clean. "
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"Please call Cluster.shutdown() to avoid this.")
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log.debug("Event loop thread was joined")
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# Ensure all connections are closed and in-flight requests cancelled
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for conn in tuple(_dispatcher_map.values()):
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conn.close()
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log.debug("Dispatchers were closed")
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class AsyncoreConnection(Connection, asyncore.dispatcher):
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"""
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An implementation of :class:`.Connection` that uses the ``asyncore``
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module in the Python standard library for its event loop.
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"""
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_loop = None
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_writable = False
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_readable = False
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@classmethod
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def initialize_reactor(cls):
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if not cls._loop:
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cls._loop = AsyncoreLoop()
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else:
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current_pid = os.getpid()
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if cls._loop._pid != current_pid:
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log.debug("Detected fork, clearing and reinitializing reactor state")
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cls.handle_fork()
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cls._loop = AsyncoreLoop()
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@classmethod
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def handle_fork(cls):
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global _dispatcher_map
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_dispatcher_map = {}
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if cls._loop:
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cls._loop._cleanup()
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cls._loop = None
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@classmethod
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def create_timer(cls, timeout, callback):
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timer = Timer(timeout, callback)
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cls._loop.add_timer(timer)
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return timer
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def __init__(self, *args, **kwargs):
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Connection.__init__(self, *args, **kwargs)
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self.deque = deque()
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self.deque_lock = Lock()
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self._connect_socket()
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asyncore.dispatcher.__init__(self, self._socket, _dispatcher_map)
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self._writable = True
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self._readable = True
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self._send_options_message()
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# start the event loop if needed
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self._loop.maybe_start()
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def close(self):
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with self.lock:
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if self.is_closed:
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return
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self.is_closed = True
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log.debug("Closing connection (%s) to %s", id(self), self.host)
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self._writable = False
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self._readable = False
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asyncore.dispatcher.close(self)
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log.debug("Closed socket to %s", self.host)
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if not self.is_defunct:
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self.error_all_requests(
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ConnectionShutdown("Connection to %s was closed" % self.host))
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#This happens when the connection is shutdown while waiting for the ReadyMessage
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if not self.connected_event.is_set():
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self.last_error = ConnectionShutdown("Connection to %s was closed" % self.host)
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# don't leave in-progress operations hanging
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self.connected_event.set()
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def handle_error(self):
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self.defunct(sys.exc_info()[1])
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def handle_close(self):
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log.debug("Connection %s closed by server", self)
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self.close()
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def handle_write(self):
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while True:
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with self.deque_lock:
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try:
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next_msg = self.deque.popleft()
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except IndexError:
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self._writable = False
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return
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try:
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sent = self.send(next_msg)
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self._readable = True
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except socket.error as err:
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if (err.args[0] in NONBLOCKING):
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with self.deque_lock:
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self.deque.appendleft(next_msg)
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else:
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self.defunct(err)
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return
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else:
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if sent < len(next_msg):
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with self.deque_lock:
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self.deque.appendleft(next_msg[sent:])
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if sent == 0:
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return
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def handle_read(self):
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try:
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while True:
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buf = self.recv(self.in_buffer_size)
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self._iobuf.write(buf)
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if len(buf) < self.in_buffer_size:
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break
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except socket.error as err:
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if ssl and isinstance(err, ssl.SSLError):
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if err.args[0] not in (ssl.SSL_ERROR_WANT_READ, ssl.SSL_ERROR_WANT_WRITE):
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self.defunct(err)
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return
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elif err.args[0] not in NONBLOCKING:
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self.defunct(err)
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return
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if self._iobuf.tell():
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self.process_io_buffer()
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if not self._requests and not self.is_control_connection:
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self._readable = False
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def push(self, data):
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sabs = self.out_buffer_size
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if len(data) > sabs:
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chunks = []
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for i in range(0, len(data), sabs):
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chunks.append(data[i:i + sabs])
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else:
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chunks = [data]
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with self.deque_lock:
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self.deque.extend(chunks)
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self._writable = True
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self._loop.wake_loop()
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def writable(self):
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return self._writable
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def readable(self):
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return self._readable or (self.is_control_connection and not (self.is_defunct or self.is_closed))
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