# 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)