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# Copyright 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 ssl
from threading import Lock, Thread
import time
from cassandra import DependencyException
from cassandra.connection import (Connection, ConnectionShutdown,
NONBLOCKING, Timer, TimerManager)
try:
import cassandra.io.libevwrapper as libev
except ImportError:
raise DependencyException(
"The C extension needed to use libev was not found. This "
"probably means that you didn't have the required build dependencies "
"when installing the driver. See "
"http://datastax.github.io/python-driver/installation.html#c-extensions "
"for instructions on installing build dependencies and building "
"the C extension.")
log = logging.getLogger(__name__)
def _cleanup(loop):
if loop:
loop._cleanup()
class LibevLoop(object):
def __init__(self):
self._pid = os.getpid()
self._loop = libev.Loop()
self._notifier = libev.Async(self._loop)
self._notifier.start()
# prevent _notifier from keeping the loop from returning
self._loop.unref()
self._started = False
self._shutdown = False
self._lock = Lock()
self._lock_thread = Lock()
self._thread = None
# set of all connections; only replaced with a new copy
# while holding _conn_set_lock, never modified in place
self._live_conns = set()
# newly created connections that need their write/read watcher started
self._new_conns = set()
# recently closed connections that need their write/read watcher stopped
self._closed_conns = set()
self._conn_set_lock = Lock()
self._preparer = libev.Prepare(self._loop, self._loop_will_run)
# prevent _preparer from keeping the loop from returning
self._loop.unref()
self._preparer.start()
self._timers = TimerManager()
self._loop_timer = libev.Timer(self._loop, self._on_loop_timer)
def maybe_start(self):
should_start = False
with self._lock:
if not self._started:
log.debug("Starting libev event loop")
self._started = True
should_start = True
if should_start:
with self._lock_thread:
if not self._shutdown:
self._thread = Thread(target=self._run_loop, name="event_loop")
self._thread.daemon = True
self._thread.start()
self._notifier.send()
def _run_loop(self):
while True:
self._loop.start()
# there are still active watchers, no deadlock
with self._lock:
if not self._shutdown and self._live_conns:
log.debug("Restarting event loop")
continue
else:
# all Connections have been closed, no active watchers
log.debug("All Connections currently closed, event loop ended")
self._started = False
break
def _cleanup(self):
self._shutdown = True
if not self._thread:
return
for conn in self._live_conns | self._new_conns | self._closed_conns:
conn.close()
for watcher in (conn._write_watcher, conn._read_watcher):
if watcher:
watcher.stop()
self.notify() # wake the timer watcher
# PYTHON-752 Thread might have just been created and not started
with self._lock_thread:
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")
def add_timer(self, timer):
self._timers.add_timer(timer)
self._notifier.send() # wake up in case this timer is earlier
def _update_timer(self):
if not self._shutdown:
next_end = self._timers.service_timeouts()
if next_end:
self._loop_timer.start(next_end - time.time()) # timer handles negative values
else:
self._loop_timer.stop()
def _on_loop_timer(self):
self._timers.service_timeouts()
def notify(self):
self._notifier.send()
def connection_created(self, conn):
with self._conn_set_lock:
new_live_conns = self._live_conns.copy()
new_live_conns.add(conn)
self._live_conns = new_live_conns
new_new_conns = self._new_conns.copy()
new_new_conns.add(conn)
self._new_conns = new_new_conns
def connection_destroyed(self, conn):
with self._conn_set_lock:
new_live_conns = self._live_conns.copy()
new_live_conns.discard(conn)
self._live_conns = new_live_conns
new_closed_conns = self._closed_conns.copy()
new_closed_conns.add(conn)
self._closed_conns = new_closed_conns
self._notifier.send()
def _loop_will_run(self, prepare):
changed = False
for conn in self._live_conns:
if not conn.deque and conn._write_watcher_is_active:
if conn._write_watcher:
conn._write_watcher.stop()
conn._write_watcher_is_active = False
changed = True
elif conn.deque and not conn._write_watcher_is_active:
conn._write_watcher.start()
conn._write_watcher_is_active = True
changed = True
if self._new_conns:
with self._conn_set_lock:
to_start = self._new_conns
self._new_conns = set()
for conn in to_start:
conn._read_watcher.start()
changed = True
if self._closed_conns:
with self._conn_set_lock:
to_stop = self._closed_conns
self._closed_conns = set()
for conn in to_stop:
if conn._write_watcher:
conn._write_watcher.stop()
# clear reference cycles from IO callback
del conn._write_watcher
if conn._read_watcher:
conn._read_watcher.stop()
# clear reference cycles from IO callback
del conn._read_watcher
changed = True
# TODO: update to do connection management, timer updates through dedicated async 'notifier' callbacks
self._update_timer()
if changed:
self._notifier.send()
_global_loop = None
atexit.register(partial(_cleanup, _global_loop))
class LibevConnection(Connection):
"""
An implementation of :class:`.Connection` that uses libev for its event loop.
"""
_write_watcher_is_active = False
_read_watcher = None
_write_watcher = None
_socket = None
@classmethod
def initialize_reactor(cls):
global _global_loop
if not _global_loop:
_global_loop = LibevLoop()
else:
if _global_loop._pid != os.getpid():
log.debug("Detected fork, clearing and reinitializing reactor state")
cls.handle_fork()
_global_loop = LibevLoop()
@classmethod
def handle_fork(cls):
global _global_loop
if _global_loop:
_global_loop._cleanup()
_global_loop = None
@classmethod
def create_timer(cls, timeout, callback):
timer = Timer(timeout, callback)
_global_loop.add_timer(timer)
return timer
def __init__(self, *args, **kwargs):
Connection.__init__(self, *args, **kwargs)
self.deque = deque()
self._deque_lock = Lock()
self._connect_socket()
self._socket.setblocking(0)
with _global_loop._lock:
self._read_watcher = libev.IO(self._socket.fileno(), libev.EV_READ, _global_loop._loop, self.handle_read)
self._write_watcher = libev.IO(self._socket.fileno(), libev.EV_WRITE, _global_loop._loop, self.handle_write)
self._send_options_message()
_global_loop.connection_created(self)
# start the global event loop if needed
_global_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.endpoint)
_global_loop.connection_destroyed(self)
self._socket.close()
log.debug("Closed socket to %s", self.endpoint)
# don't leave in-progress operations hanging
if not self.is_defunct:
self.error_all_requests(
ConnectionShutdown("Connection to %s was closed" % self.endpoint))
def handle_write(self, watcher, revents, errno=None):
if revents & libev.EV_ERROR:
if errno:
exc = IOError(errno, os.strerror(errno))
else:
exc = Exception("libev reported an error")
self.defunct(exc)
return
while True:
try:
with self._deque_lock:
next_msg = self.deque.popleft()
except IndexError:
if not self._socket_writable:
self._socket_writable = True
return
try:
sent = self._socket.send(next_msg)
except socket.error as err:
if (err.args[0] in NONBLOCKING or
err.args[0] in (ssl.SSL_ERROR_WANT_READ, ssl.SSL_ERROR_WANT_WRITE)):
if err.args[0] in NONBLOCKING:
self._socket_writable = False
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:])
# we've seen some cases that 0 is returned instead of NONBLOCKING. But usually,
# we don't expect this to happen. https://bugs.python.org/issue20951
if sent == 0:
self._socket_writable = False
return
def handle_read(self, watcher, revents, errno=None):
if revents & libev.EV_ERROR:
if errno:
exc = IOError(errno, os.strerror(errno))
else:
exc = Exception("libev reported an error")
self.defunct(exc)
return
try:
while True:
buf = self._socket.recv(self.in_buffer_size)
self._iobuf.write(buf)
if len(buf) < self.in_buffer_size:
break
except socket.error as err:
if isinstance(err, ssl.SSLError):
if err.args[0] in (ssl.SSL_ERROR_WANT_READ, ssl.SSL_ERROR_WANT_WRITE):
if not self._iobuf.tell():
return
else:
self.defunct(err)
return
elif err.args[0] in NONBLOCKING:
if not self._iobuf.tell():
return
else:
self.defunct(err)
return
if self._iobuf.tell():
self.process_io_buffer()
else:
log.debug("Connection %s closed by server", self)
self.close()
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)
_global_loop.notify()
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