Source code for cassandra.io.asyncorereactor
# Copyright 2013-2015 DataStax, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import atexit
from collections import deque
from functools import partial
import logging
import os
import socket
import sys
from threading import Event, Lock, Thread
import time
import weakref
from six.moves import range
try:
from weakref import WeakSet
except ImportError:
from cassandra.util import WeakSet # noqa
import asyncore
try:
import ssl
except ImportError:
ssl = None # NOQA
from cassandra.connection import (Connection, ConnectionShutdown,
ConnectionException, NONBLOCKING,
Timer, TimerManager)
log = logging.getLogger(__name__)
def _cleanup(loop_weakref):
try:
loop = loop_weakref()
except ReferenceError:
return
loop._cleanup()
class AsyncoreLoop(object):
def __init__(self):
self._pid = os.getpid()
self._loop_lock = Lock()
self._started = False
self._shutdown = False
self._thread = None
self._timers = TimerManager()
atexit.register(partial(_cleanup, weakref.ref(self)))
def maybe_start(self):
should_start = False
did_acquire = False
try:
did_acquire = self._loop_lock.acquire(False)
if did_acquire and not self._started:
self._started = True
should_start = True
finally:
if did_acquire:
self._loop_lock.release()
if should_start:
self._thread = Thread(target=self._run_loop, name="cassandra_driver_event_loop")
self._thread.daemon = True
self._thread.start()
def _run_loop(self):
log.debug("Starting asyncore event loop")
with self._loop_lock:
while not self._shutdown:
try:
asyncore.loop(timeout=0.001, use_poll=True, count=100)
self._timers.service_timeouts()
if not asyncore.socket_map:
time.sleep(0.005)
except Exception:
log.debug("Asyncore event loop stopped unexepectedly", exc_info=True)
break
self._started = False
log.debug("Asyncore event loop ended")
def add_timer(self, timer):
self._timers.add_timer(timer)
def _cleanup(self):
self._shutdown = True
if not self._thread:
return
log.debug("Waiting for event loop thread to join...")
self._thread.join(timeout=1.0)
if self._thread.is_alive():
log.warning(
"Event loop thread could not be joined, so shutdown may not be clean. "
"Please call Cluster.shutdown() to avoid this.")
log.debug("Event loop thread was joined")
[docs]class AsyncoreConnection(Connection, asyncore.dispatcher):
"""
An implementation of :class:`.Connection` that uses the ``asyncore``
module in the Python standard library for its event loop.
"""
_loop = None
_writable = False
_readable = False
@classmethod
def initialize_reactor(cls):
if not cls._loop:
cls._loop = AsyncoreLoop()
else:
current_pid = os.getpid()
if cls._loop._pid != current_pid:
log.debug("Detected fork, clearing and reinitializing reactor state")
cls.handle_fork()
cls._loop = AsyncoreLoop()
@classmethod
def handle_fork(cls):
if cls._loop:
cls._loop._cleanup()
cls._loop = None
@classmethod
def create_timer(cls, timeout, callback):
timer = Timer(timeout, callback)
cls._loop.add_timer(timer)
return timer
def __init__(self, *args, **kwargs):
Connection.__init__(self, *args, **kwargs)
asyncore.dispatcher.__init__(self)
self.deque = deque()
self.deque_lock = Lock()
self._connect_socket()
asyncore.dispatcher.__init__(self, self._socket)
self._writable = True
self._readable = True
self._send_options_message()
# start the event loop if needed
self._loop.maybe_start()
def close(self):
with self.lock:
if self.is_closed:
return
self.is_closed = True
log.debug("Closing connection (%s) to %s", id(self), self.host)
self._writable = False
self._readable = False
asyncore.dispatcher.close(self)
log.debug("Closed socket to %s", self.host)
if not self.is_defunct:
self.error_all_requests(
ConnectionShutdown("Connection to %s was closed" % self.host))
# don't leave in-progress operations hanging
self.connected_event.set()
def handle_error(self):
self.defunct(sys.exc_info()[1])
def handle_close(self):
log.debug("Connection %s closed by server", self)
self.close()
def handle_write(self):
while True:
with self.deque_lock:
try:
next_msg = self.deque.popleft()
except IndexError:
self._writable = False
return
try:
sent = self.send(next_msg)
self._readable = True
except socket.error as err:
if (err.args[0] in NONBLOCKING):
with self.deque_lock:
self.deque.appendleft(next_msg)
else:
self.defunct(err)
return
else:
if sent < len(next_msg):
with self.deque_lock:
self.deque.appendleft(next_msg[sent:])
if sent == 0:
return
def handle_read(self):
try:
while True:
buf = self.recv(self.in_buffer_size)
self._iobuf.write(buf)
if len(buf) < self.in_buffer_size:
break
except socket.error as err:
if ssl and isinstance(err, ssl.SSLError):
if err.args[0] not in (ssl.SSL_ERROR_WANT_READ, ssl.SSL_ERROR_WANT_WRITE):
self.defunct(err)
return
elif err.args[0] not in NONBLOCKING:
self.defunct(err)
return
if self._iobuf.tell():
self.process_io_buffer()
if not self._requests and not self.is_control_connection:
self._readable = False
def push(self, data):
sabs = self.out_buffer_size
if len(data) > sabs:
chunks = []
for i in range(0, len(data), sabs):
chunks.append(data[i:i + sabs])
else:
chunks = [data]
with self.deque_lock:
self.deque.extend(chunks)
self._writable = True
def writable(self):
return self._writable
def readable(self):
return self._readable or (self.is_control_connection and not (self.is_defunct or self.is_closed))