# Source code for cassandra.io.eventletreactor

    # Copyright 2014 Symantec Corporation
    # 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.

    # Originally derived from MagnetoDB source:
    #   https://github.com/stackforge/magnetodb/blob/2015.1.0b1/magnetodb/common/cassandra/io/eventletreactor.py

    import eventlet
    from eventlet.green import socket
    from eventlet.queue import Queue
    from greenlet import GreenletExit
    import logging
    from threading import Event
    import time

    from six.moves import xrange

    from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager

    log = logging.getLogger(__name__)

    class EventletConnection(Connection):
        """
        An implementation of :class:`.Connection` that utilizes ``eventlet``.

        This implementation assumes all eventlet monkey patching is active. It is not tested with partial patching.
        """

        _read_watcher = None
        _write_watcher = None

        _socket_impl = eventlet.green.socket
        _ssl_impl = eventlet.green.ssl

        _timers = None
        _timeout_watcher = None
        _new_timer = None

        @classmethod
        def initialize_reactor(cls):
            eventlet.monkey_patch()
            if not cls._timers:
                cls._timers = TimerManager()
                cls._timeout_watcher = eventlet.spawn(cls.service_timeouts)
                cls._new_timer = Event()

        @classmethod
        def create_timer(cls, timeout, callback):
            timer = Timer(timeout, callback)
            cls._timers.add_timer(timer)
            cls._new_timer.set()
            return timer

        @classmethod
        def service_timeouts(cls):
            """
            cls._timeout_watcher runs in this loop forever.
            It is usually waiting for the next timeout on the cls._new_timer Event.
            When new timers are added, that event is set so that the watcher can
            wake up and possibly set an earlier timeout.
            """
            timer_manager = cls._timers
            while True:
                next_end = timer_manager.service_timeouts()
                sleep_time = max(next_end - time.time(), 0) if next_end else 10000
                cls._new_timer.wait(sleep_time)
                cls._new_timer.clear()

        def __init__(self, *args, **kwargs):
            Connection.__init__(self, *args, **kwargs)
            self._write_queue = Queue()

            self._connect_socket()

            self._read_watcher = eventlet.spawn(lambda: self.handle_read())
            self._write_watcher = eventlet.spawn(lambda: self.handle_write())
            self._send_options_message()

        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))

            cur_gthread = eventlet.getcurrent()

            if self._read_watcher and self._read_watcher != cur_gthread:
                self._read_watcher.kill()
            if self._write_watcher and self._write_watcher != cur_gthread:
                self._write_watcher.kill()
            if self._socket:
                self._socket.close()
            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_close(self):
            log.debug("connection closed by server")
            self.close()

        def handle_write(self):
            while True:
                try:
                    next_msg = self._write_queue.get()
                    self._socket.sendall(next_msg)
                except socket.error as err:
                    log.debug("Exception during socket send for %s: %s", self, err)
                    self.defunct(err)
                    return  # Leave the write loop
                except GreenletExit:  # graceful greenthread exit
                    return

        def handle_read(self):
            while True:
                try:
                    buf = self._socket.recv(self.in_buffer_size)
                    self._iobuf.write(buf)
                except socket.error as err:
                    log.debug("Exception during socket recv for %s: %s",
                              self, err)
                    self.defunct(err)
                    return  # leave the read loop
                except GreenletExit:  # graceful greenthread exit
                    return

                if buf and self._iobuf.tell():
                    self.process_io_buffer()
                else:
                    log.debug("Connection %s closed by server", self)
                    self.close()
                    return

        def push(self, data):
            chunk_size = self.out_buffer_size
            for i in xrange(0, len(data), chunk_size):
                self._write_queue.put(data[i:i + chunk_size])