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  # Copyright 2010 United States Government as represented by the
  # Administrator of the National Aeronautics and Space Administration.
  # All Rights Reserved.
  # Copyright 2011 - 2012, Red Hat, 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.
  
  """
  Shared code between AMQP based openstack.common.rpc implementations.
  
  The code in this module is shared between the rpc implemenations based on AMQP.
  Specifically, this includes impl_kombu and impl_qpid.  impl_carrot also uses
  AMQP, but is deprecated and predates this code.
  """
  
  import collections
  import inspect
  import sys
  import uuid
  
  from eventlet import greenpool
  from eventlet import pools
  from eventlet import queue
  from eventlet import semaphore
  from oslo.config import cfg
  
  from keystone.openstack.common import excutils
  from keystone.openstack.common.gettextutils import _  # noqa
  from keystone.openstack.common import local
  from keystone.openstack.common import log as logging
  from keystone.openstack.common.rpc import common as rpc_common
  
  
  amqp_opts = [
      cfg.BoolOpt('amqp_durable_queues',
                  default=False,
                  deprecated_name='rabbit_durable_queues',
                  deprecated_group='DEFAULT',
                  help='Use durable queues in amqp.'),
      cfg.BoolOpt('amqp_auto_delete',
                  default=False,
                  help='Auto-delete queues in amqp.'),
  ]
  
  cfg.CONF.register_opts(amqp_opts)
  
  UNIQUE_ID = '_unique_id'
  LOG = logging.getLogger(__name__)
  
  
  class Pool(pools.Pool):
      """Class that implements a Pool of Connections."""
      def __init__(self, conf, connection_cls, *args, **kwargs):
          self.connection_cls = connection_cls
          self.conf = conf
          kwargs.setdefault("max_size", self.conf.rpc_conn_pool_size)
          kwargs.setdefault("order_as_stack", True)
          super(Pool, self).__init__(*args, **kwargs)
          self.reply_proxy = None
  
      # TODO(comstud): Timeout connections not used in a while
      def create(self):
          LOG.debug(_('Pool creating new connection'))
          return self.connection_cls(self.conf)
  
      def empty(self):
          while self.free_items:
              self.get().close()
          # Force a new connection pool to be created.
          # Note that this was added due to failing unit test cases. The issue
          # is the above "while loop" gets all the cached connections from the
          # pool and closes them, but never returns them to the pool, a pool
          # leak. The unit tests hang waiting for an item to be returned to the
          # pool. The unit tests get here via the tearDown() method. In the run
          # time code, it gets here via cleanup() and only appears in service.py
          # just before doing a sys.exit(), so cleanup() only happens once and
          # the leakage is not a problem.
          self.connection_cls.pool = None
  
  
  _pool_create_sem = semaphore.Semaphore()
  
  
  def get_connection_pool(conf, connection_cls):
      with _pool_create_sem:
          # Make sure only one thread tries to create the connection pool.
          if not connection_cls.pool:
              connection_cls.pool = Pool(conf, connection_cls)
      return connection_cls.pool
  
  
  class ConnectionContext(rpc_common.Connection):
      """The class that is actually returned to the create_connection() caller.
  
      This is essentially a wrapper around Connection that supports 'with'.
      It can also return a new Connection, or one from a pool.
  
      The function will also catch when an instance of this class is to be
      deleted.  With that we can return Connections to the pool on exceptions
      and so forth without making the caller be responsible for catching them.
      If possible the function makes sure to return a connection to the pool.
      """
  
      def __init__(self, conf, connection_pool, pooled=True, server_params=None):
          """Create a new connection, or get one from the pool."""
          self.connection = None
          self.conf = conf
          self.connection_pool = connection_pool
          if pooled:
              self.connection = connection_pool.get()
          else:
              self.connection = connection_pool.connection_cls(
                  conf,
                  server_params=server_params)
          self.pooled = pooled
  
      def __enter__(self):
          """When with ConnectionContext() is used, return self."""
          return self
  
      def _done(self):
          """If the connection came from a pool, clean it up and put it back.
          If it did not come from a pool, close it.
          """
          if self.connection:
              if self.pooled:
                  # Reset the connection so it's ready for the next caller
                  # to grab from the pool
                  self.connection.reset()
                  self.connection_pool.put(self.connection)
              else:
                  try:
                      self.connection.close()
                  except Exception:
                      pass
              self.connection = None
  
      def __exit__(self, exc_type, exc_value, tb):
          """End of 'with' statement.  We're done here."""
          self._done()
  
      def __del__(self):
          """Caller is done with this connection.  Make sure we cleaned up."""
          self._done()
  
      def close(self):
          """Caller is done with this connection."""
          self._done()
  
      def create_consumer(self, topic, proxy, fanout=False):
          self.connection.create_consumer(topic, proxy, fanout)
  
      def create_worker(self, topic, proxy, pool_name):
          self.connection.create_worker(topic, proxy, pool_name)
  
      def join_consumer_pool(self, callback, pool_name, topic, exchange_name,
                             ack_on_error=True):
          self.connection.join_consumer_pool(callback,
                                             pool_name,
                                             topic,
                                             exchange_name,
                                             ack_on_error)
  
      def consume_in_thread(self):
          self.connection.consume_in_thread()
  
      def __getattr__(self, key):
          """Proxy all other calls to the Connection instance."""
          if self.connection:
              return getattr(self.connection, key)
          else:
              raise rpc_common.InvalidRPCConnectionReuse()
  
  
  class ReplyProxy(ConnectionContext):
      """Connection class for RPC replies / callbacks."""
      def __init__(self, conf, connection_pool):
          self._call_waiters = {}
          self._num_call_waiters = 0
          self._num_call_waiters_wrn_threshhold = 10
          self._reply_q = 'reply_' + uuid.uuid4().hex
          super(ReplyProxy, self).__init__(conf, connection_pool, pooled=False)
          self.declare_direct_consumer(self._reply_q, self._process_data)
          self.consume_in_thread()
  
      def _process_data(self, message_data):
          msg_id = message_data.pop('_msg_id', None)
          waiter = self._call_waiters.get(msg_id)
          if not waiter:
              LOG.warn(_('No calling threads waiting for msg_id : %(msg_id)s'
                         ', message : %(data)s'), {'msg_id': msg_id,
                                                   'data': message_data})
              LOG.warn(_('_call_waiters: %s') % str(self._call_waiters))
          else:
              waiter.put(message_data)
  
      def add_call_waiter(self, waiter, msg_id):
          self._num_call_waiters += 1
          if self._num_call_waiters > self._num_call_waiters_wrn_threshhold:
              LOG.warn(_('Number of call waiters is greater than warning '
                         'threshhold: %d. There could be a MulticallProxyWaiter '
                         'leak.') % self._num_call_waiters_wrn_threshhold)
              self._num_call_waiters_wrn_threshhold *= 2
          self._call_waiters[msg_id] = waiter
  
      def del_call_waiter(self, msg_id):
          self._num_call_waiters -= 1
          del self._call_waiters[msg_id]
  
      def get_reply_q(self):
          return self._reply_q
  
  
  def msg_reply(conf, msg_id, reply_q, connection_pool, reply=None,
                failure=None, ending=False, log_failure=True):
      """Sends a reply or an error on the channel signified by msg_id.
  
      Failure should be a sys.exc_info() tuple.
  
      """
      with ConnectionContext(conf, connection_pool) as conn:
          if failure:
              failure = rpc_common.serialize_remote_exception(failure,
                                                              log_failure)
  
          msg = {'result': reply, 'failure': failure}
          if ending:
              msg['ending'] = True
          _add_unique_id(msg)
          # If a reply_q exists, add the msg_id to the reply and pass the
          # reply_q to direct_send() to use it as the response queue.
          # Otherwise use the msg_id for backward compatibilty.
          if reply_q:
              msg['_msg_id'] = msg_id
              conn.direct_send(reply_q, rpc_common.serialize_msg(msg))
          else:
              conn.direct_send(msg_id, rpc_common.serialize_msg(msg))
  
  
  class RpcContext(rpc_common.CommonRpcContext):
      """Context that supports replying to a rpc.call."""
      def __init__(self, **kwargs):
          self.msg_id = kwargs.pop('msg_id', None)
          self.reply_q = kwargs.pop('reply_q', None)
          self.conf = kwargs.pop('conf')
          super(RpcContext, self).__init__(**kwargs)
  
      def deepcopy(self):
          values = self.to_dict()
          values['conf'] = self.conf
          values['msg_id'] = self.msg_id
          values['reply_q'] = self.reply_q
          return self.__class__(**values)
  
      def reply(self, reply=None, failure=None, ending=False,
                connection_pool=None, log_failure=True):
          if self.msg_id:
              msg_reply(self.conf, self.msg_id, self.reply_q, connection_pool,
                        reply, failure, ending, log_failure)
              if ending:
                  self.msg_id = None
  
  
  def unpack_context(conf, msg):
      """Unpack context from msg."""
      context_dict = {}
      for key in list(msg.keys()):
          # NOTE(vish): Some versions of python don't like unicode keys
          #             in kwargs.
          key = str(key)
          if key.startswith('_context_'):
              value = msg.pop(key)
              context_dict[key[9:]] = value
      context_dict['msg_id'] = msg.pop('_msg_id', None)
      context_dict['reply_q'] = msg.pop('_reply_q', None)
      context_dict['conf'] = conf
      ctx = RpcContext.from_dict(context_dict)
      rpc_common._safe_log(LOG.debug, _('unpacked context: %s'), ctx.to_dict())
      return ctx
  
  
  def pack_context(msg, context):
      """Pack context into msg.
  
      Values for message keys need to be less than 255 chars, so we pull
      context out into a bunch of separate keys. If we want to support
      more arguments in rabbit messages, we may want to do the same
      for args at some point.
  
      """
      if isinstance(context, dict):
          context_d = dict([('_context_%s' % key, value)
                            for (key, value) in context.iteritems()])
      else:
          context_d = dict([('_context_%s' % key, value)
                            for (key, value) in context.to_dict().iteritems()])
  
      msg.update(context_d)
  
  
  class _MsgIdCache(object):
      """This class checks any duplicate messages."""
  
      # NOTE: This value is considered can be a configuration item, but
      #       it is not necessary to change its value in most cases,
      #       so let this value as static for now.
      DUP_MSG_CHECK_SIZE = 16
  
      def __init__(self, **kwargs):
          self.prev_msgids = collections.deque([],
                                               maxlen=self.DUP_MSG_CHECK_SIZE)
  
      def check_duplicate_message(self, message_data):
          """AMQP consumers may read same message twice when exceptions occur
             before ack is returned. This method prevents doing it.
          """
          if UNIQUE_ID in message_data:
              msg_id = message_data[UNIQUE_ID]
              if msg_id not in self.prev_msgids:
                  self.prev_msgids.append(msg_id)
              else:
                  raise rpc_common.DuplicateMessageError(msg_id=msg_id)
  
  
  def _add_unique_id(msg):
      """Add unique_id for checking duplicate messages."""
      unique_id = uuid.uuid4().hex
      msg.update({UNIQUE_ID: unique_id})
      LOG.debug(_('UNIQUE_ID is %s.') % (unique_id))
  
  
  class _ThreadPoolWithWait(object):
      """Base class for a delayed invocation manager.
  
      Used by the Connection class to start up green threads
      to handle incoming messages.
      """
  
      def __init__(self, conf, connection_pool):
          self.pool = greenpool.GreenPool(conf.rpc_thread_pool_size)
          self.connection_pool = connection_pool
          self.conf = conf
  
      def wait(self):
          """Wait for all callback threads to exit."""
          self.pool.waitall()
  
  
  class CallbackWrapper(_ThreadPoolWithWait):
      """Wraps a straight callback.
  
      Allows it to be invoked in a green thread.
      """
  
      def __init__(self, conf, callback, connection_pool):
          """Initiates CallbackWrapper object.
  
          :param conf: cfg.CONF instance
          :param callback: a callable (probably a function)
          :param connection_pool: connection pool as returned by
                                  get_connection_pool()
          """
          super(CallbackWrapper, self).__init__(
              conf=conf,
              connection_pool=connection_pool,
          )
          self.callback = callback
  
      def __call__(self, message_data):
          self.pool.spawn_n(self.callback, message_data)
  
  
  class ProxyCallback(_ThreadPoolWithWait):
      """Calls methods on a proxy object based on method and args."""
  
      def __init__(self, conf, proxy, connection_pool):
          super(ProxyCallback, self).__init__(
              conf=conf,
              connection_pool=connection_pool,
          )
          self.proxy = proxy
          self.msg_id_cache = _MsgIdCache()
  
      def __call__(self, message_data):
          """Consumer callback to call a method on a proxy object.
  
          Parses the message for validity and fires off a thread to call the
          proxy object method.
  
          Message data should be a dictionary with two keys:
              method: string representing the method to call
              args: dictionary of arg: value
  
          Example: {'method': 'echo', 'args': {'value': 42}}
  
          """
          # It is important to clear the context here, because at this point
          # the previous context is stored in local.store.context
          if hasattr(local.store, 'context'):
              del local.store.context
          rpc_common._safe_log(LOG.debug, _('received %s'), message_data)
          self.msg_id_cache.check_duplicate_message(message_data)
          ctxt = unpack_context(self.conf, message_data)
          method = message_data.get('method')
          args = message_data.get('args', {})
          version = message_data.get('version')
          namespace = message_data.get('namespace')
          if not method:
              LOG.warn(_('no method for message: %s') % message_data)
              ctxt.reply(_('No method for message: %s') % message_data,
                         connection_pool=self.connection_pool)
              return
          self.pool.spawn_n(self._process_data, ctxt, version, method,
                            namespace, args)
  
      def _process_data(self, ctxt, version, method, namespace, args):
          """Process a message in a new thread.
  
          If the proxy object we have has a dispatch method
          (see rpc.dispatcher.RpcDispatcher), pass it the version,
          method, and args and let it dispatch as appropriate.  If not, use
          the old behavior of magically calling the specified method on the
          proxy we have here.
          """
          ctxt.update_store()
          try:
              rval = self.proxy.dispatch(ctxt, version, method, namespace,
                                         **args)
              # Check if the result was a generator
              if inspect.isgenerator(rval):
                  for x in rval:
                      ctxt.reply(x, None, connection_pool=self.connection_pool)
              else:
                  ctxt.reply(rval, None, connection_pool=self.connection_pool)
              # This final None tells multicall that it is done.
              ctxt.reply(ending=True, connection_pool=self.connection_pool)
          except rpc_common.ClientException as e:
              LOG.debug(_('Expected exception during message handling (%s)') %
                        e._exc_info[1])
              ctxt.reply(None, e._exc_info,
                         connection_pool=self.connection_pool,
                         log_failure=False)
          except Exception:
              # sys.exc_info() is deleted by LOG.exception().
              exc_info = sys.exc_info()
              LOG.error(_('Exception during message handling'),
                        exc_info=exc_info)
              ctxt.reply(None, exc_info, connection_pool=self.connection_pool)
  
  
  class MulticallProxyWaiter(object):
      def __init__(self, conf, msg_id, timeout, connection_pool):
          self._msg_id = msg_id
          self._timeout = timeout or conf.rpc_response_timeout
          self._reply_proxy = connection_pool.reply_proxy
          self._done = False
          self._got_ending = False
          self._conf = conf
          self._dataqueue = queue.LightQueue()
          # Add this caller to the reply proxy's call_waiters
          self._reply_proxy.add_call_waiter(self, self._msg_id)
          self.msg_id_cache = _MsgIdCache()
  
      def put(self, data):
          self._dataqueue.put(data)
  
      def done(self):
          if self._done:
              return
          self._done = True
          # Remove this caller from reply proxy's call_waiters
          self._reply_proxy.del_call_waiter(self._msg_id)
  
      def _process_data(self, data):
          result = None
          self.msg_id_cache.check_duplicate_message(data)
          if data['failure']:
              failure = data['failure']
              result = rpc_common.deserialize_remote_exception(self._conf,
                                                               failure)
          elif data.get('ending', False):
              self._got_ending = True
          else:
              result = data['result']
          return result
  
      def __iter__(self):
          """Return a result until we get a reply with an 'ending' flag."""
          if self._done:
              raise StopIteration
          while True:
              try:
                  data = self._dataqueue.get(timeout=self._timeout)
                  result = self._process_data(data)
              except queue.Empty:
                  self.done()
                  raise rpc_common.Timeout()
              except Exception:
                  with excutils.save_and_reraise_exception():
                      self.done()
              if self._got_ending:
                  self.done()
                  raise StopIteration
              if isinstance(result, Exception):
                  self.done()
                  raise result
              yield result
  
  
  def create_connection(conf, new, connection_pool):
      """Create a connection."""
      return ConnectionContext(conf, connection_pool, pooled=not new)
  
  
  _reply_proxy_create_sem = semaphore.Semaphore()
  
  
  def multicall(conf, context, topic, msg, timeout, connection_pool):
      """Make a call that returns multiple times."""
      LOG.debug(_('Making synchronous call on %s ...'), topic)
      msg_id = uuid.uuid4().hex
      msg.update({'_msg_id': msg_id})
      LOG.debug(_('MSG_ID is %s') % (msg_id))
      _add_unique_id(msg)
      pack_context(msg, context)
  
      with _reply_proxy_create_sem:
          if not connection_pool.reply_proxy:
              connection_pool.reply_proxy = ReplyProxy(conf, connection_pool)
      msg.update({'_reply_q': connection_pool.reply_proxy.get_reply_q()})
      wait_msg = MulticallProxyWaiter(conf, msg_id, timeout, connection_pool)
      with ConnectionContext(conf, connection_pool) as conn:
          conn.topic_send(topic, rpc_common.serialize_msg(msg), timeout)
      return wait_msg
  
  
  def call(conf, context, topic, msg, timeout, connection_pool):
      """Sends a message on a topic and wait for a response."""
      rv = multicall(conf, context, topic, msg, timeout, connection_pool)
      # NOTE(vish): return the last result from the multicall
      rv = list(rv)
      if not rv:
          return
      return rv[-1]
  
  
  def cast(conf, context, topic, msg, connection_pool):
      """Sends a message on a topic without waiting for a response."""
      LOG.debug(_('Making asynchronous cast on %s...'), topic)
      _add_unique_id(msg)
      pack_context(msg, context)
      with ConnectionContext(conf, connection_pool) as conn:
          conn.topic_send(topic, rpc_common.serialize_msg(msg))
  
  
  def fanout_cast(conf, context, topic, msg, connection_pool):
      """Sends a message on a fanout exchange without waiting for a response."""
      LOG.debug(_('Making asynchronous fanout cast...'))
      _add_unique_id(msg)
      pack_context(msg, context)
      with ConnectionContext(conf, connection_pool) as conn:
          conn.fanout_send(topic, rpc_common.serialize_msg(msg))
  
  
  def cast_to_server(conf, context, server_params, topic, msg, connection_pool):
      """Sends a message on a topic to a specific server."""
      _add_unique_id(msg)
      pack_context(msg, context)
      with ConnectionContext(conf, connection_pool, pooled=False,
                             server_params=server_params) as conn:
          conn.topic_send(topic, rpc_common.serialize_msg(msg))
  
  
  def fanout_cast_to_server(conf, context, server_params, topic, msg,
                            connection_pool):
      """Sends a message on a fanout exchange to a specific server."""
      _add_unique_id(msg)
      pack_context(msg, context)
      with ConnectionContext(conf, connection_pool, pooled=False,
                             server_params=server_params) as conn:
          conn.fanout_send(topic, rpc_common.serialize_msg(msg))
  
  
  def notify(conf, context, topic, msg, connection_pool, envelope):
      """Sends a notification event on a topic."""
      LOG.debug(_('Sending %(event_type)s on %(topic)s'),
                dict(event_type=msg.get('event_type'),
                     topic=topic))
      _add_unique_id(msg)
      pack_context(msg, context)
      with ConnectionContext(conf, connection_pool) as conn:
          if envelope:
              msg = rpc_common.serialize_msg(msg)
          conn.notify_send(topic, msg)
  
  
  def cleanup(connection_pool):
      if connection_pool:
          connection_pool.empty()
  
  
  def get_control_exchange(conf):
      return conf.control_exchange
  