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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.
"""
Module that implements an event loop based on twisted
( https://twistedmatrix.com ).
"""
import atexit
import logging
import time
from functools import partial
from threading import Thread, Lock
import weakref
from twisted.internet import reactor, protocol
from twisted.internet.endpoints import connectProtocol, TCP4ClientEndpoint, SSL4ClientEndpoint
from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
from twisted.python.failure import Failure
from zope.interface import implementer
from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager, ConnectionException
try:
from OpenSSL import SSL
_HAS_SSL = True
except ImportError as e:
_HAS_SSL = False
import_exception = e
log = logging.getLogger(__name__)
def _cleanup(cleanup_weakref):
try:
cleanup_weakref()._cleanup()
except ReferenceError:
return
class TwistedConnectionProtocol(protocol.Protocol):
"""
Twisted Protocol class for handling data received and connection
made events.
"""
def __init__(self, connection):
self.connection = connection
def dataReceived(self, data):
"""
Callback function that is called when data has been received
on the connection.
Reaches back to the Connection object and queues the data for
processing.
"""
self.connection._iobuf.write(data)
self.connection.handle_read()
def connectionMade(self):
"""
Callback function that is called when a connection has succeeded.
Reaches back to the Connection object and confirms that the connection
is ready.
"""
self.connection.client_connection_made(self.transport)
def connectionLost(self, reason):
# reason is a Failure instance
log.debug("Connect lost: %s", reason)
self.connection.defunct(reason.value)
class TwistedLoop(object):
_lock = None
_thread = None
_timeout_task = None
_timeout = None
def __init__(self):
self._lock = Lock()
self._timers = TimerManager()
def maybe_start(self):
with self._lock:
if not reactor.running:
self._thread = Thread(target=reactor.run,
name="cassandra_driver_twisted_event_loop",
kwargs={'installSignalHandlers': False})
self._thread.daemon = True
self._thread.start()
atexit.register(partial(_cleanup, weakref.ref(self)))
def _cleanup(self):
if self._thread:
reactor.callFromThread(reactor.stop)
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)
# callFromThread to schedule from the loop thread, where
# the timeout task can safely be modified
reactor.callFromThread(self._schedule_timeout, timer.end)
def _schedule_timeout(self, next_timeout):
if next_timeout:
delay = max(next_timeout - time.time(), 0)
if self._timeout_task and self._timeout_task.active():
if next_timeout < self._timeout:
self._timeout_task.reset(delay)
self._timeout = next_timeout
else:
self._timeout_task = reactor.callLater(delay, self._on_loop_timer)
self._timeout = next_timeout
def _on_loop_timer(self):
self._timers.service_timeouts()
self._schedule_timeout(self._timers.next_timeout)
@implementer(IOpenSSLClientConnectionCreator)
class _SSLCreator(object):
def __init__(self, endpoint, ssl_context, ssl_options, check_hostname, timeout):
self.endpoint = endpoint
self.ssl_options = ssl_options
self.check_hostname = check_hostname
self.timeout = timeout
if ssl_context:
self.context = ssl_context
else:
self.context = SSL.Context(SSL.TLSv1_METHOD)
if "certfile" in self.ssl_options:
self.context.use_certificate_file(self.ssl_options["certfile"])
if "keyfile" in self.ssl_options:
self.context.use_privatekey_file(self.ssl_options["keyfile"])
if "ca_certs" in self.ssl_options:
self.context.load_verify_locations(self.ssl_options["ca_certs"])
if "cert_reqs" in self.ssl_options:
self.context.set_verify(
self.ssl_options["cert_reqs"],
callback=self.verify_callback
)
self.context.set_info_callback(self.info_callback)
def verify_callback(self, connection, x509, errnum, errdepth, ok):
return ok
def info_callback(self, connection, where, ret):
if where & SSL.SSL_CB_HANDSHAKE_DONE:
if self.check_hostname and self.endpoint.address != connection.get_peer_certificate().get_subject().commonName:
transport = connection.get_app_data()
transport.failVerification(Failure(ConnectionException("Hostname verification failed", self.endpoint)))
def clientConnectionForTLS(self, tlsProtocol):
connection = SSL.Connection(self.context, None)
connection.set_app_data(tlsProtocol)
if self.ssl_options and "server_hostname" in self.ssl_options:
connection.set_tlsext_host_name(self.ssl_options['server_hostname'].encode('ascii'))
return connection
class TwistedConnection(Connection):
"""
An implementation of :class:`.Connection` that utilizes the
Twisted event loop.
"""
_loop = None
@classmethod
def initialize_reactor(cls):
if not cls._loop:
cls._loop = TwistedLoop()
@classmethod
def create_timer(cls, timeout, callback):
timer = Timer(timeout, callback)
cls._loop.add_timer(timer)
return timer
def __init__(self, *args, **kwargs):
"""
Initialization method.
Note that we can't call reactor methods directly here because
it's not thread-safe, so we schedule the reactor/connection
stuff to be run from the event loop thread when it gets the
chance.
"""
Connection.__init__(self, *args, **kwargs)
self.is_closed = True
self.connector = None
self.transport = None
reactor.callFromThread(self.add_connection)
self._loop.maybe_start()
def _check_pyopenssl(self):
if self.ssl_context or self.ssl_options:
if not _HAS_SSL:
raise ImportError(
str(import_exception) +
', pyOpenSSL must be installed to enable SSL support with the Twisted event loop'
)
def add_connection(self):
"""
Convenience function to connect and store the resulting
connector.
"""
host, port = self.endpoint.resolve()
if self.ssl_context or self.ssl_options:
# Can't use optionsForClientTLS here because it *forces* hostname verification.
# Cool they enforce strong security, but we have to be able to turn it off
self._check_pyopenssl()
ssl_connection_creator = _SSLCreator(
self.endpoint,
self.ssl_context if self.ssl_context else None,
self.ssl_options,
self._check_hostname,
self.connect_timeout,
)
endpoint = SSL4ClientEndpoint(
reactor,
host,
port,
sslContextFactory=ssl_connection_creator,
timeout=self.connect_timeout,
)
else:
endpoint = TCP4ClientEndpoint(
reactor,
host,
port,
timeout=self.connect_timeout
)
connectProtocol(endpoint, TwistedConnectionProtocol(self))
def client_connection_made(self, transport):
"""
Called by twisted protocol when a connection attempt has
succeeded.
"""
with self.lock:
self.is_closed = False
self.transport = transport
self._send_options_message()
def close(self):
"""
Disconnect and error-out all requests.
"""
with self.lock:
if self.is_closed:
return
self.is_closed = True
log.debug("Closing connection (%s) to %s", id(self), self.endpoint)
reactor.callFromThread(self.transport.connector.disconnect)
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 handle_read(self):
"""
Process the incoming data buffer.
"""
self.process_io_buffer()
def push(self, data):
"""
This function is called when outgoing data should be queued
for sending.
Note that we can't call transport.write() directly because
it is not thread-safe, so we schedule it to run from within
the event loop when it gets the chance.
"""
reactor.callFromThread(self.transport.write, data)
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