text: # Copyright 2009-2015 MongoDB, 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.
  
  """Tools for connecting to MongoDB.
  
  .. seealso:: Module :mod:`~pymongo.master_slave_connection` for
     connecting to master-slave clusters, and
     :doc:`/examples/high_availability` for an example of how to connect
     to a replica set, or specify a list of mongos instances for automatic
     failover.
  
  To get a :class:`~pymongo.database.Database` instance from a
  :class:`MongoClient` use either dictionary-style or attribute-style
  access:
  
  .. doctest::
  
    >>> from pymongo import MongoClient
    >>> c = MongoClient()
    >>> c.test_database
    Database(MongoClient('localhost', 27017), u'test_database')
    >>> c['test-database']
    Database(MongoClient('localhost', 27017), u'test-database')
  """
  
  import datetime
  import random
  import socket
  import struct
  import threading
  import time
  import warnings
  
  from bson.binary import PYTHON_LEGACY
  from bson.codec_options import CodecOptions
  from bson.py3compat import b
  from pymongo import (auth,
                       common,
                       database,
                       helpers,
                       message,
                       pool,
                       thread_util,
                       uri_parser)
  from pymongo.common import HAS_SSL
  from pymongo.cursor_manager import CursorManager
  from pymongo.errors import (AutoReconnect,
                              ConfigurationError,
                              ConnectionFailure,
                              DocumentTooLarge,
                              DuplicateKeyError,
                              InvalidURI,
                              OperationFailure)
  from pymongo.member import Member
  from pymongo.read_preferences import ReadPreference, _ServerMode
  
  
  EMPTY = b("")
  
  
  def _partition_node(node):
      """Split a host:port string returned from mongod/s into
      a (host, int(port)) pair needed for socket.connect().
      """
      host = node
      port = 27017
      idx = node.rfind(':')
      if idx != -1:
          host, port = node[:idx], int(node[idx + 1:])
      if host.startswith('['):
          host = host[1:-1]
      return host, port
  
  
  class MongoClient(common.BaseObject):
      """Connection to MongoDB.
      """
  
      HOST = "localhost"
      PORT = 27017
      _rs_client = False
  
      def __init__(self, host=None, port=None, max_pool_size=100,
                   document_class=dict, tz_aware=False, **kwargs):
          """Create a new connection to a single MongoDB instance at *host:port*.
  
          The resultant client object has connection-pooling built
          in. It also performs auto-reconnection when necessary. If an
          operation fails because of a connection error,
          :class:`~pymongo.errors.ConnectionFailure` is raised. If
          auto-reconnection will be performed,
          :class:`~pymongo.errors.AutoReconnect` will be
          raised. Application code should handle this exception
          (recognizing that the operation failed) and then continue to
          execute.
  
          Raises :class:`TypeError` if port is not an instance of
          ``int``. Raises :class:`~pymongo.errors.ConnectionFailure` if
          the connection cannot be made.
  
          The `host` parameter can be a full `mongodb URI
          <http://dochub.mongodb.org/core/connections>`_, in addition to
          a simple hostname. It can also be a list of hostnames or
          URIs. Any port specified in the host string(s) will override
          the `port` parameter. If multiple mongodb URIs containing
          database or auth information are passed, the last database,
          username, and password present will be used.  For username and
          passwords reserved characters like ':', '/', '+' and '@' must be
          escaped following RFC 2396.
  
          :Parameters:
            - `host` (optional): hostname or IP address of the
              instance to connect to, or a mongodb URI, or a list of
              hostnames / mongodb URIs. If `host` is an IPv6 literal
              it must be enclosed in '[' and ']' characters following
              the RFC2732 URL syntax (e.g. '[::1]' for localhost)
            - `port` (optional): port number on which to connect
            - `max_pool_size` (optional): The maximum number of connections
              that the pool will open simultaneously. If this is set, operations
              will block if there are `max_pool_size` outstanding connections
              from the pool. Defaults to 100. Cannot be 0.
            - `document_class` (optional): default class to use for
              documents returned from queries on this client
            - `tz_aware` (optional): if ``True``,
              :class:`~datetime.datetime` instances returned as values
              in a document by this :class:`MongoClient` will be timezone
              aware (otherwise they will be naive)
  
            | **Other optional parameters can be passed as keyword arguments:**
  
            - `maxPoolSize` (optional): Alias for max_pool_size. Takes
              precedence over max_pool_size.
            - `socketTimeoutMS`: (integer or None) How long (in milliseconds) a
              send or receive on a socket can take before timing out. Defaults to
              ``None`` (no timeout).
            - `connectTimeoutMS`: (integer or None) How long (in milliseconds) a
              connection can take to be opened before timing out. Defaults to
              ``20000``.
            - `waitQueueTimeoutMS`: (integer or None) How long (in milliseconds)
              a thread will wait for a socket from the pool if the pool has no
              free sockets. Defaults to ``None`` (no timeout).
            - `waitQueueMultiple`: (integer or None) Multiplied by max_pool_size
              to give the number of threads allowed to wait for a socket at one
              time. Defaults to ``None`` (no waiters).
            - `socketKeepAlive`: (boolean) Whether to send periodic keep-alive
              packets on connected sockets. Defaults to ``False`` (do not send
              keep-alive packets).
            - `connect`: if True (the default), immediately connect to MongoDB in
              the foreground. Otherwise connect on the first operation.
  
            | **Write Concern options:**
            | (Only set if passed. No default values.)
  
            - `w`: (integer or string) If this is a replica set, write operations
              will block until they have been replicated to the specified number
              or tagged set of servers. `w=<int>` always includes the replica set
              primary (e.g. w=3 means write to the primary and wait until
              replicated to **two** secondaries). Passing w=0 **disables write
              acknowledgement** and all other write concern options.
            - `wtimeout`: (integer) Used in conjunction with `w`. Specify a value
              in milliseconds to control how long to wait for write propagation
              to complete. If replication does not complete in the given
              timeframe, a timeout exception is raised.
            - `j`: If ``True`` block until write operations have been committed
              to the journal. Cannot be used in combination with `fsync`. Prior
              to MongoDB 2.6 this option was ignored if the server was running
              without journaling. Starting with MongoDB 2.6 write operations will
              fail with an exception if this option is used when the server is
              running without journaling.
            - `fsync`: If ``True`` and the server is running without journaling,
              blocks until the server has synced all data files to disk. If the
              server is running with journaling, this acts the same as the `j`
              option, blocking until write operations have been committed to the
              journal. Cannot be used in combination with `j`.
  
            | **Replica set keyword arguments for connecting with a replica set
              - either directly or via a mongos:**
            | (ignored by standalone mongod instances)
  
            - `replicaSet`: (string or None) The name of the replica set to
              connect to. The driver will verify that the replica set it connects
              to matches this name. Implies that the hosts specified are a seed
              list and the driver should attempt to find all members of the set.
              *Ignored by mongos*. Defaults to ``None``.
            - `read_preference`: The read preference for this client. If
              connecting to a secondary then a read preference mode *other* than
              primary is required - otherwise all queries will throw
              :class:`~pymongo.errors.AutoReconnect` "not master".
              See :mod:`~pymongo.read_preferences` for options.
              Defaults to ``ReadPreference.PRIMARY``.
            - `localThresholdMS`: (integer) Used with mongos high availability.
              Any known mongos whose ping time is within localThresholdMS of the
              nearest member may be chosen during a failover. Default 15
              milliseconds. Ignored **by** mongos and must be configured on the
              command line. See the localThreshold_ option for more information.
  
            | **SSL configuration:**
  
            - `ssl`: If ``True``, create the connection to the server using SSL.
              Defaults to ``False``.
            - `ssl_keyfile`: The private keyfile used to identify the local
              connection against mongod.  If included with the ``certfile`` then
              only the ``ssl_certfile`` is needed.  Implies ``ssl=True``.
              Defaults to ``None``.
            - `ssl_certfile`: The certificate file used to identify the local
              connection against mongod. Implies ``ssl=True``. Defaults to
              ``None``.
            - `ssl_cert_reqs`: Specifies whether a certificate is required from
              the other side of the connection, and whether it will be validated
              if provided. It must be one of the three values ``ssl.CERT_NONE``
              (certificates ignored), ``ssl.CERT_OPTIONAL``
              (not required, but validated if provided), or ``ssl.CERT_REQUIRED``
              (required and validated). If the value of this parameter is not
              ``ssl.CERT_NONE``, then the ``ssl_ca_certs`` parameter must point
              to a file of CA certificates. Implies ``ssl=True``. Defaults to
              ``ssl.CERT_NONE``.
            - `ssl_ca_certs`: The ca_certs file contains a set of concatenated
              "certification authority" certificates, which are used to validate
              certificates passed from the other end of the connection.
              Implies ``ssl=True``. Defaults to ``None``.
            - `ssl_match_hostname`: If ``True`` (the default), and
              `ssl_cert_reqs` is not ``ssl.CERT_NONE``, enables hostname
              verification using the :func:`~ssl.match_hostname` function from
              python's :mod:`~ssl` module. Think very carefully before setting
              this to ``False`` as that could make your application vulnerable to
              man-in-the-middle attacks.
  
          .. seealso:: :meth:`end_request`
  
          .. mongodoc:: connections
  
          .. versionchanged:: 2.5
             Added additional ssl options
          .. versionadded:: 2.4
          """
          if host is None:
              host = self.HOST
          if isinstance(host, basestring):
              host = [host]
          if port is None:
              port = self.PORT
          if not isinstance(port, int):
              raise TypeError("port must be an instance of int")
  
          seeds = set()
          username = None
          password = None
          self.__default_database_name = None
          opts = {}
          for entity in host:
              if "://" in entity:
                  if entity.startswith("mongodb://"):
                      res = uri_parser.parse_uri(entity, port)
                      seeds.update(res["nodelist"])
                      username = res["username"] or username
                      password = res["password"] or password
                      self.__default_database_name = (
                          res["database"] or self.__default_database_name)
  
                      opts = res["options"]
                  else:
                      idx = entity.find("://")
                      raise InvalidURI("Invalid URI scheme: "
                                       "%s" % (entity[:idx],))
              else:
                  seeds.update(uri_parser.split_hosts(entity, port))
          if not seeds:
              raise ConfigurationError("need to specify at least one host")
  
          # Seeds are only used before first connection attempt; nodes are then
          # used for any reconnects. Nodes are set to all replica set members
          # if connecting to a replica set (besides arbiters), or to all
          # available mongoses from the seed list, or to the one standalone
          # mongod.
          self.__seeds = frozenset(seeds)
          self.__nodes = frozenset()
          self.__member = None  # TODO: Rename to __server.
  
          # _pool_class and _event_class are for deep customization of PyMongo,
          # e.g. Motor. SHOULD NOT BE USED BY THIRD-PARTY DEVELOPERS.
          pool_class = kwargs.pop('_pool_class', pool.Pool)
          event_class = kwargs.pop('_event_class', None)
  
          # tag_sets is only supported through kwargs since it must be a list.
          if "tag_sets" in kwargs:
              warnings.warn("tag_sets is deprecated in this version of PyMongo "
                            "and removed in PyMongo 3. Pass a read preference "
                            "object as read_preference instead",
                            DeprecationWarning, stacklevel=2)
  
          # Support _ServerMode through kwargs
          pref = kwargs.get("read_preference")
          if isinstance(pref, _ServerMode):
              kwargs["read_preference"] = pref.mode
              kwargs["tag_sets"] = pref.tag_sets
  
          # URI overrides kwargs.
          options = {}
          for option, value in kwargs.iteritems():
              option, value = common.validate(option, value)
              options[option] = value
          options.update(opts)
  
          # Both of these work in kwargs and URI...
          if ("secondary_acceptable_latency_ms" in options or
                  "secondaryacceptablelatencyms" in options):
              warnings.warn("secondary_acceptable_latency_ms and "
                            "secondaryAcceptableLatencyMS are deprecated. Use "
                            "localThresholdMS instead",
                            DeprecationWarning, stacklevel=2)
  
          # localthresholdms takes precedence over secondaryacceptablelatencyms.
          if "localthresholdms" in options:
              options.pop("secondaryacceptablelatencyms", None)
              options.pop("secondary_acceptable_latency_ms", None)
              options["secondaryacceptablelatencyms"] = (
                  options["localthresholdms"])
  
          common.validate_boolean('tz_aware', tz_aware)
          uuid_representation = options.pop('uuidrepresentation', PYTHON_LEGACY)
          options['codec_options'] = CodecOptions(
              document_class, tz_aware, uuid_representation)
  
          self.__max_pool_size = options.get(
              'maxpoolsize',
              common.validate_positive_integer_or_none(
                  'max_pool_size', max_pool_size))
  
          self.__cursor_manager = CursorManager(self)
  
          self.__repl = options.get('replicaset')
          self.__direct = len(seeds) == 1 and not self.__repl
  
          self.__net_timeout = options.get('sockettimeoutms')
          self.__conn_timeout = options.get('connecttimeoutms', 20.0)
          self.__wait_queue_timeout = options.get('waitqueuetimeoutms')
          self.__wait_queue_multiple = options.get('waitqueuemultiple')
          self.__socket_keepalive = options.get('socketkeepalive', False)
  
          self.__use_ssl = options.get('ssl')
          self.__ssl_keyfile = options.get('ssl_keyfile')
          self.__ssl_certfile = options.get('ssl_certfile')
          self.__ssl_cert_reqs = options.get('ssl_cert_reqs')
          self.__ssl_ca_certs = options.get('ssl_ca_certs')
          self.__ssl_match_hostname = options.get('ssl_match_hostname', True)
  
          ssl_kwarg_keys = [k for k in kwargs.keys()
                            if k.startswith('ssl_') and kwargs[k]]
          if self.__use_ssl == False and ssl_kwarg_keys:
              raise ConfigurationError("ssl has not been enabled but the "
                                       "following ssl parameters have been set: "
                                       "%s. Please set `ssl=True` or remove."
                                       % ', '.join(ssl_kwarg_keys))
  
          if self.__ssl_cert_reqs and not self.__ssl_ca_certs:
              raise ConfigurationError("If `ssl_cert_reqs` is not "
                                       "`ssl.CERT_NONE` then you must "
                                       "include `ssl_ca_certs` to be able "
                                       "to validate the server.")
  
          if ssl_kwarg_keys and self.__use_ssl is None:
              # ssl options imply ssl = True
              self.__use_ssl = True
  
          if self.__use_ssl and not HAS_SSL:
              raise ConfigurationError("The ssl module is not available. If you "
                                       "are using a python version previous to "
                                       "2.6 you must install the ssl package "
                                       "from PyPI.")
  
          self.__use_greenlets = options.get('use_greenlets', False)
          self.__pool_class = pool_class
  
          self.__connecting = False
          if self.__use_greenlets:
              warnings.warn("use_greenlets is deprecated in this version of "
                            "PyMongo and removed in PyMongo 3. Use Gevent's "
                            "monkey.patch_all() instead.",
                            DeprecationWarning, stacklevel=2)
              # Greenlets don't need to lock around access to the Member;
              # they're only interrupted when they do I/O.
              self.__connecting_lock = thread_util.DummyLock()
          else:
              self.__connecting_lock = threading.Lock()
  
          if event_class:
              self.__event_class = event_class
          else:
              # Prevent a cycle; this lambda shouldn't refer to self.
              g = self.__use_greenlets
              event_class = lambda: thread_util.create_event(g)
              self.__event_class = event_class
  
          self.__future_member = None
          self.__auto_start_request = options.get('auto_start_request', False)
  
          # cache of existing indexes used by ensure_index ops
          self.__index_cache = {}
          self.__auth_credentials = {}
  
          super(MongoClient, self).__init__(**options)
          if self.slave_okay:
              warnings.warn("slave_okay is deprecated in this version of "
                            "PyMongo and removed in PyMongo 3. Use "
                            "secondaryPreferred read preference instead.",
                            DeprecationWarning, stacklevel=2)
  
          _connect = options.get('_connect', options.get('connect', True))
          if _connect:
              try:
                  self._ensure_connected(True)
              except AutoReconnect, e:
                  # ConnectionFailure makes more sense here than AutoReconnect
                  raise ConnectionFailure(str(e))
  
          if username:
              mechanism = options.get('authmechanism', 'DEFAULT')
              source = (
                  options.get('authsource')
                  or self.__default_database_name
                  or 'admin')
  
              credentials = auth._build_credentials_tuple(mechanism,
                                                          source,
                                                          username,
                                                          password,
                                                          options)
              try:
                  self._cache_credentials(source, credentials, _connect)
              except OperationFailure, exc:
                  raise ConfigurationError(str(exc))
  
      def _cached(self, dbname, coll, index):
          """Test if `index` is cached.
          """
          cache = self.__index_cache
          now = datetime.datetime.utcnow()
          return (dbname in cache and
                  coll in cache[dbname] and
                  index in cache[dbname][coll] and
                  now < cache[dbname][coll][index])
  
      def _cache_index(self, database, collection, index, cache_for):
          """Add an index to the index cache for ensure_index operations.
          """
          now = datetime.datetime.utcnow()
          expire = datetime.timedelta(seconds=cache_for) + now
  
          if database not in self.__index_cache:
              self.__index_cache[database] = {}
              self.__index_cache[database][collection] = {}
              self.__index_cache[database][collection][index] = expire
  
          elif collection not in self.__index_cache[database]:
              self.__index_cache[database][collection] = {}
              self.__index_cache[database][collection][index] = expire
  
          else:
              self.__index_cache[database][collection][index] = expire
  
      def _purge_index(self, database_name,
                       collection_name=None, index_name=None):
          """Purge an index from the index cache.
  
          If `index_name` is None purge an entire collection.
  
          If `collection_name` is None purge an entire database.
          """
          if not database_name in self.__index_cache:
              return
  
          if collection_name is None:
              del self.__index_cache[database_name]
              return
  
          if not collection_name in self.__index_cache[database_name]:
              return
  
          if index_name is None:
              del self.__index_cache[database_name][collection_name]
              return
  
          if index_name in self.__index_cache[database_name][collection_name]:
              del self.__index_cache[database_name][collection_name][index_name]
  
      def _cache_credentials(self, source, credentials, connect=True):
          """Add credentials to the database authentication cache
          for automatic login when a socket is created. If `connect` is True,
          verify the credentials on the server first.
          """
          if source in self.__auth_credentials:
              # Nothing to do if we already have these credentials.
              if credentials == self.__auth_credentials[source]:
                  return
              raise OperationFailure('Another user is already authenticated '
                                     'to this database. You must logout first.')
  
          if connect:
              member = self.__ensure_member()
              sock_info = self.__socket(member)
              try:
                  # Since __check_auth was called in __socket
                  # there is no need to call it here.
                  auth.authenticate(credentials, sock_info, self.__simple_command)
                  sock_info.authset.add(credentials)
              finally:
                  member.maybe_return_socket(sock_info)
  
          self.__auth_credentials[source] = credentials
  
      def _purge_credentials(self, source):
          """Purge credentials from the database authentication cache.
          """
          if source in self.__auth_credentials:
              del self.__auth_credentials[source]
  
      def __create_pool(self, pair):
          return self.__pool_class(
              pair,
              self.__max_pool_size,
              self.__net_timeout,
              self.__conn_timeout,
              self.__use_ssl,
              use_greenlets=self.__use_greenlets,
              ssl_keyfile=self.__ssl_keyfile,
              ssl_certfile=self.__ssl_certfile,
              ssl_cert_reqs=self.__ssl_cert_reqs,
              ssl_ca_certs=self.__ssl_ca_certs,
              ssl_match_hostname=self.__ssl_match_hostname,
              wait_queue_timeout=self.__wait_queue_timeout,
              wait_queue_multiple=self.__wait_queue_multiple,
              socket_keepalive=self.__socket_keepalive)
  
      def __check_auth(self, sock_info):
          """Authenticate using cached database credentials.
          """
          if self.__auth_credentials or sock_info.authset:
              cached = set(self.__auth_credentials.itervalues())
  
              authset = sock_info.authset.copy()
  
              # Logout any credentials that no longer exist in the cache.
              for credentials in authset - cached:
                  self.__simple_command(sock_info, credentials[1], {'logout': 1})
                  sock_info.authset.discard(credentials)
  
              for credentials in cached - authset:
                  auth.authenticate(credentials,
                                    sock_info, self.__simple_command)
                  sock_info.authset.add(credentials)
  
      def __member_property(self, attr_name, default=None):
          member = self.__member
          if member:
              return getattr(member, attr_name)
  
          return default
  
      @property
      def host(self):
          """**DEPRECATED** Current connected host.
  
          .. warning:: :attr:`host` is deprecated in this version of PyMongo and
            removed in PyMongo 3.0. Use :attr:`address` instead.
  
          .. versionchanged:: 2.9
             Deprecated :attr:`host`.
          .. versionchanged:: 1.3
             ``host`` is now a property rather than a method.
          """
          warnings.warn("host is deprecated in this version of PyMongo and "
                        "removed in PyMongo 3. Use address instead.",
                        DeprecationWarning, stacklevel=2)
          member = self.__member
          if member:
              return member.host[0]
  
          return None
  
      @property
      def port(self):
          """**DEPRECATED** Current connected port.
  
          .. warning:: :attr:`port` is deprecated in this version of PyMongo and
            removed in PyMongo 3.0. Use :attr:`address` instead.
  
          .. versionchanged:: 2.9
             Deprecated :attr:`port`.
          .. versionchanged:: 1.3
             ``port`` is now a property rather than a method.
          """
          warnings.warn("port is deprecated in this version of PyMongo and "
                        "removed in PyMongo 3. Use address instead.",
                        DeprecationWarning, stacklevel=2)
          member = self.__member
          if member:
              return member.host[1]
  
      @property
      def address(self):
          """(host, port) of the current standalone, primary, or mongos, or None.
  
          .. versionadded:: 2.9
          """
          member = self.__member
          if member:
              return member.host
          return None
  
      @property
      def is_primary(self):
          """If this instance is connected to a standalone, a replica set
          primary, or the master of a master-slave set.
  
          .. versionadded:: 2.3
          """
          return self.__member_property('is_primary', False)
  
      @property
      def is_mongos(self):
          """If this instance is connected to mongos.
  
          .. versionadded:: 2.3
          """
          return self.__member_property('is_mongos', False)
  
      @property
      def max_pool_size(self):
          """The maximum number of sockets the pool will open concurrently.
  
          When the pool has reached `max_pool_size`, operations block waiting for
          a socket to be returned to the pool. If ``waitQueueTimeoutMS`` is set,
          a blocked operation will raise :exc:`~pymongo.errors.ConnectionFailure`
          after a timeout. By default ``waitQueueTimeoutMS`` is not set.
  
          .. warning:: SIGNIFICANT BEHAVIOR CHANGE in 2.6. Previously, this
            parameter would limit only the idle sockets the pool would hold
            onto, not the number of open sockets. The default has also changed
            to 100.
  
          .. versionchanged:: 2.6
          .. versionadded:: 1.11
          """
          return self.__max_pool_size
  
      @property
      def use_greenlets(self):
          """**DEPRECATED** Whether calling :meth:`start_request` assigns
          greenlet-local, rather than thread-local, sockets.
  
          .. warning:: :attr:`use_greenlets` is deprecated in this version of
            PyMongo and removed in PyMongo 3. Use Gevent's monkey.patch_all()
            instead.
  
          .. versionchanged:: 2.9
            Deprecated use_greenlets.
          .. versionadded:: 2.4.2
          """
          warnings.warn("use_greenlets is deprecated in this version of PyMongo "
                        "and removed in PyMongo 3. Use Gevent's "
                        "monkey.patch_all() instead.",
                        DeprecationWarning, stacklevel=2)
          return self.__use_greenlets
  
      @property
      def nodes(self):
          """List of all known nodes.
  
          Nodes are either specified when this instance was created,
          or discovered through the replica set discovery mechanism.
  
          .. versionadded:: 1.8
          """
          return self.__nodes
  
      @property
      def auto_start_request(self):
          """**DEPRECATED** Is auto_start_request enabled?
  
          .. versionchanged:: 2.8
            Deprecated auto_start_request.
          """
          warnings.warn("auto_start_request is deprecated in this version of "
                        "PyMongo and removed in PyMongo 3.",
                        DeprecationWarning, stacklevel=2)
          return self.__auto_start_request
  
      def get_document_class(self):
          """**DEPRECATED** Default class to use for documents returned from this
          client.
  
          .. warning:: :attr:`document_class` is deprecated in this version of
            PyMongo and removed in PyMongo 3. Use
            :class:`~bson.codec_options.CodecOptions` with
            :meth:`~pymongo.mongo_client.MongoClient.get_database`,
            :meth:`~pymongo.database.Database.get_collection`,
            or :meth:`~pymongo.collection.Collection.with_options` instead.
            See the :doc:`/migrate-to-pymongo3` for examples.
  
          .. versionchanged:: 2.9
            Deprecated document_class.
          .. versionadded:: 1.7
          """
          warnings.warn("document_class is deprecated in this version of "
                        "PyMongo and removed in PyMongo 3. See the "
                        "document_class docstring for more information.",
                        DeprecationWarning, stacklevel=2)
          return self._codec_options.document_class
  
      def set_document_class(self, klass):
          """document_class setter"""
          warnings.warn("document_class is deprecated in this version of "
                        "PyMongo and removed in PyMongo 3. See the "
                        "document_class docstring for more information.",
                        DeprecationWarning, stacklevel=2)
          tz_aware = self._codec_options.tz_aware
          uuid_rep = self._codec_options.uuid_representation
          self._codec_options = CodecOptions(klass, tz_aware, uuid_rep)
  
      document_class = property(get_document_class, set_document_class)
  
      @property
      def tz_aware(self):
          """**DEPRECATED** Does this client return timezone-aware datetimes?
  
          .. warning:: :attr:`tz_aware` is deprecated in this version of PyMongo
            and removed in PyMongo 3. Use :attr:`codec_options` instead.
  
          .. versionchanged:: 2.9
            Deprecated tz_aware.
          .. versionadded:: 1.8
          """
          warnings.warn("tz_aware is deprecated in this version of PyMongo and "
                        "removed in PyMongo 3. Use codec_options instead.",
                        DeprecationWarning, stacklevel=2)
          return self._codec_options.tz_aware
  
      @property
      def max_bson_size(self):
          """Return the maximum size BSON object the connected server
          accepts in bytes. Defaults to 16MB if not connected to a
          server.
  
          .. versionadded:: 1.10
          """
          return self.__member_property('max_bson_size', common.MAX_BSON_SIZE)
  
      @property
      def max_message_size(self):
          """Return the maximum message size the connected server
          accepts in bytes. Defaults to 32MB if not connected to a
          server.
  
          .. versionadded:: 2.6
          """
          return self.__member_property(
              'max_message_size', common.MAX_MESSAGE_SIZE)
  
      @property
      def min_wire_version(self):
          """The minWireVersion reported by the server.
  
          Returns ``0`` when connected to server versions prior to MongoDB 2.6.
  
          .. versionadded:: 2.7
          """
          return self.__member_property(
              'min_wire_version', common.MIN_WIRE_VERSION)
  
      @property
      def max_wire_version(self):
          """The maxWireVersion reported by the server.
  
          Returns ``0`` when connected to server versions prior to MongoDB 2.6.
  
          .. versionadded:: 2.7
          """
          return self.__member_property(
              'max_wire_version', common.MAX_WIRE_VERSION)
  
      @property
      def max_write_batch_size(self):
          """The maxWriteBatchSize reported by the server.
  
          Returns a default value when connected to server versions prior to
          MongoDB 2.6.
  
          .. versionadded:: 2.7
          """
          return self.__member_property(
              'max_write_batch_size', common.MAX_WRITE_BATCH_SIZE)
  
      @property
      def local_threshold_ms(self):
          """Any replica set member whose ping time is within
          :attr:`local_threshold_ms` of the nearest member may accept reads.
          Defaults to 15 milliseconds.
  
          .. versionadded:: 2.9
          """
          return self._secondary_acceptable_latency_ms
  
      def __simple_command(self, sock_info, dbname, spec):
          """Send a command to the server. May raise AutoReconnect.
          """
          ns = dbname + '.$cmd'
          rqst_id, msg, _ = message.query(0, ns, 0, -1, spec)
          start = time.time()
          try:
              sock_info.sock.sendall(msg)
              response = self.__receive_message_on_socket(1, rqst_id, sock_info)
          except socket.error, e:
              sock_info.close()
              raise AutoReconnect(e)
          except:
              sock_info.close()
              raise
  
          end = time.time()
          response = helpers._unpack_response(response)['data'][0]
          msg = "command %s on namespace %s failed: %%s" % (
              repr(spec).replace("%", "%%"), ns)
          helpers._check_command_response(response, None, msg)
          return response, end - start
  
      def __try_node(self, node):
          """Try to connect to this node and see if it works for our connection
          type. Returns a Member and set of hosts (including this one). Doesn't
          modify state.
  
          :Parameters:
           - `node`: The (host, port) pair to try.
          """
          # Call 'ismaster' directly so we can get a response time.
          connection_pool = self.__create_pool(node)
          sock_info = connection_pool.get_socket()
          try:
              response, res_time = self.__simple_command(sock_info,
                                                         'admin',
                                                         {'ismaster': 1})
          finally:
              connection_pool.maybe_return_socket(sock_info)
  
          member = Member(
              node,
              connection_pool,
              response,
              res_time)
  
          nodes = frozenset([node])
  
          # Replica Set?
          if not self.__direct:
              # Check that this host is part of the given replica set.
              if self.__repl and member.set_name != self.__repl:
                  raise ConfigurationError("%s:%d is not a member of "
                                           "replica set %s"
                                           % (node[0], node[1], self.__repl))
  
              if "hosts" in response:
                  nodes = frozenset([
                      _partition_node(h) for h in response["hosts"]])
  
              if member.is_primary:
                  return member, nodes
  
              elif "primary" in response:
                  # Shortcut: a secondary usually tells us who the primary is.
                  candidate = _partition_node(response["primary"])
                  return self.__try_node(candidate)
  
              # Explain why we aren't using this connection.
              raise AutoReconnect('%s:%d is not primary or master' % node)
  
          # Direct connection
          if member.is_arbiter and not self.__direct:
              raise ConfigurationError("%s:%d is an arbiter" % node)
  
          return member, nodes
  
      def __pick_nearest(self, candidates):
          """Return the 'nearest' Member instance based on response time.
  
          Doesn't modify state.
          """
          latency = self.secondary_acceptable_latency_ms
          # Only used for mongos high availability, ping_time is in seconds.
          fastest = min([
              member.ping_time for member in candidates])
  
          near_candidates = [
              member for member in candidates
              if member.ping_time - fastest <= latency / 1000.0]
  
          return random.choice(near_candidates)
  
      def __ensure_member(self):
          """Connect and return a Member instance, or raise AutoReconnect."""
          # If `connecting` is False, no thread is in __find_node(),
          # and `future_member` is resolved. `member` may be None if the
          # last __find_node() attempt failed, otherwise it is in `nodes`.
          #
          # If `connecting` is True, a thread is in __find_node(),
          # `member` is None, and `future_member` is pending.
          #
          # To violate these invariants temporarily, acquire the lock.
          # Note that close() interacts with this method.
          self.__connecting_lock.acquire()
          if self.__member:
              member = self.__member
              self.__connecting_lock.release()
              return member
  
          elif self.__connecting:
              # A thread is in __find_node(). Wait.
              future = self.__future_member
              self.__connecting_lock.release()
              return future.result()
  
          else:
              self.__connecting = True
              future = self.__future_member = thread_util.Future(
                  self.__event_class)
  
              self.__connecting_lock.release()
  
              member = None
              nodes = None
              exc = None
  
              try:
                  try:
                      member, nodes = self.__find_node()
                      return member
                  except Exception, e:
                      exc = e
                      raise
              finally:
                  # We're either returning a Member or raising an error.
                  # Propagate either outcome to waiting threads.
                  self.__connecting_lock.acquire()
                  self.__member = member
                  self.__connecting = False
  
                  # If we discovered a set of nodes, use them from now on;
                  # otherwise we're raising an error. Stick with the last
                  # known good set of nodes.
                  if nodes:
                      self.__nodes = nodes
  
                  if member:
                      # Unblock waiting threads.
                      future.set_result(member)
                  else:
                      # Raise exception in waiting threads.
                      future.set_exception(exc)
  
                  self.__connecting_lock.release()
  
      def __find_node(self):
          """Find a server suitable for our connection type.
  
          Returns a Member and a set of nodes. Doesn't modify state.
  
          If only one host was supplied to __init__ see if we can connect
          to it. Don't check if the host is a master/primary so we can make
          a direct connection to read from a secondary or send commands to
          an arbiter.
  
          If more than one host was supplied treat them as a seed list for
          connecting to a replica set or to support high availability for
          mongos. If connecting to a replica set try to find the primary,
          and set `nodes` to list of all members.
  
          If a mongos seed list was provided find the "nearest" mongos and
          return it, setting `nodes` to all mongoses in the seed list that
          are up.
  
          Otherwise we iterate through the list trying to find a host we can
          send write operations to.
          """
          assert not self.__member, \
              "__find_node unexpectedly running with a non-null Member"
  
          errors = []
          mongos_candidates = []
          candidates = self.__nodes or self.__seeds
          chosen_member = None
          discovered_nodes = None
  
          for candidate in candidates:
              try:
                  member, nodes = self.__try_node(candidate)
                  if member.is_mongos and not self.__direct:
                      mongos_candidates.append(member)
  
                      # We intend to find all the mongoses; keep trying nodes.
                      continue
                  elif len(mongos_candidates):
                      raise ConfigurationError("Seed list cannot contain a mix "
                                               "of mongod and mongos instances.")
  
                  # We've found a suitable node.
                  chosen_member = member
                  discovered_nodes = nodes
                  break
              except (OperationFailure, ConfigurationError, ValueError):
                  # The server is available but something failed, e.g. auth,
                  # wrong replica set name, or incompatible wire protocol.
                  raise
              except Exception, why:
                  errors.append(str(why))
  
          if len(mongos_candidates):
              # If we have a mongos seed list, pick the "nearest" member.
              chosen_member = self.__pick_nearest(mongos_candidates)
              mongoses = frozenset(m.host for m in mongos_candidates)
  
              # The first time, __nodes is empty and mongoses becomes nodes.
              return chosen_member, self.__nodes or mongoses
  
          if not chosen_member:
              # Couldn't find a suitable host.
              raise AutoReconnect(', '.join(errors))
  
          return chosen_member, discovered_nodes
  
      def __socket(self, member):
          """Get a SocketInfo.
  
          Calls close() on error.
          """
          try:
              if self.__auto_start_request and not member.in_request():
                  member.start_request()
  
              sock_info = member.get_socket()
          except socket.error, why:
              self.close()
  
              # Check if a unix domain socket
              host, port = member.host
              if host.endswith('.sock'):
                  host_details = "%s:" % host
              else:
                  host_details = "%s:%d:" % (host, port)
              raise AutoReconnect("could not connect to "
                                  "%s %s" % (host_details, str(why)))
          try:
              self.__check_auth(sock_info)
          except:
              member.maybe_return_socket(sock_info)
              raise
          return sock_info
  
      def _ensure_connected(self, sync=False):
          """Ensure this client instance is connected to a mongod/s.
          """
          self.__ensure_member()
  
      def disconnect(self):
          """**DEPRECATED** Disconnect from MongoDB.
  
          Disconnecting will close all underlying sockets in the connection
          pool. If this instance is used again it will be automatically
          re-opened. Care should be taken to make sure that :meth:`disconnect`
          is not called in the middle of a sequence of operations in which
          ordering is important. This could lead to unexpected results.
  
          .. warning:: :meth:`disconnect` is deprecated in this version of
            PyMongo and removed in PyMongo 3. Use :meth:`close` instead.
  
          .. seealso:: :meth:`end_request`
          .. versionchanged:: 2.9
            Deprecated.
          .. versionadded:: 1.3
          """
          warnings.warn("disconnect is deprecated in this version of PyMongo "
                        "and removed in PyMongo 3. Use close() instead.",
                        DeprecationWarning, stacklevel=2)
          self.close()
  
      def close(self):
          """Disconnect from MongoDB.
  
          Disconnecting will close all underlying sockets in the connection
          pool. If this instance is used again it will be automatically
          re-opened. Care should be taken to make sure that :meth:`close`
          is not called in the middle of a sequence of operations in which
          ordering is important. This could lead to unexpected results.
  
          .. seealso:: :meth:`end_request`
          .. versionadded:: 2.1
          """
          self.__connecting_lock.acquire()
          member, self.__member = self.__member, None
          self.__connecting_lock.release()
  
          # Close sockets promptly.
          if member:
              member.reset()
  
      def alive(self):
          """**DEPRECATED** Return ``False`` if there has been an error
          communicating with the server, else ``True``.
  
          This method attempts to check the status of the server with minimal I/O.
          The current thread / greenlet retrieves a socket from the pool (its
          request socket if it's in a request, or a random idle socket if it's not
          in a request) and checks whether calling `select`_ on it raises an
          error. If there are currently no idle sockets, :meth:`alive` will
          attempt to actually connect to the server.
  
          A more certain way to determine server availability is::
  
              client.admin.command('ping')
  
          .. _select: http://docs.python.org/2/library/select.html#select.select
          """
          warnings.warn("alive is deprecated in this version of PyMongo and "
                        "removed in PyMongo 3.",
                        DeprecationWarning, stacklevel=2)
          # In the common case, a socket is available and was used recently, so
          # calling select() on it is a reasonable attempt to see if the OS has
          # reported an error.
          self.__connecting_lock.acquire()
          member = self.__member
          self.__connecting_lock.release()
          if not member:
              return False
          else:
              sock_info = None
              try:
                  try:
                      sock_info = member.get_socket()
                      return not pool._closed(sock_info.sock)
                  except (socket.error, ConnectionFailure):
                      return False
              finally:
                  member.maybe_return_socket(sock_info)
  
      def set_cursor_manager(self, manager_class):
          """Set this client's cursor manager.
  
          Raises :class:`TypeError` if `manager_class` is not a subclass of
          :class:`~pymongo.cursor_manager.CursorManager`. A cursor manager
          handles closing cursors. Different managers can implement different
          policies in terms of when to actually kill a cursor that has
          been closed.
  
          :Parameters:
            - `manager_class`: cursor manager to use
  
          .. versionchanged:: 2.9
             Unedprecated.
          .. versionchanged:: 2.1+
             Deprecated support for external cursor managers.
          """
          manager = manager_class(self)
          if not isinstance(manager, CursorManager):
              raise TypeError("manager_class must be a subclass of "
                              "CursorManager")
  
          self.__cursor_manager = manager
  
      def __check_response_to_last_error(self, response, is_command):
          """Check a response to a lastError message for errors.
  
          `response` is a byte string representing a response to the message.
          If it represents an error response we raise OperationFailure.
  
          Return the response as a document.
          """
          response = helpers._unpack_response(response)
  
          assert response["number_returned"] == 1
          result = response["data"][0]
  
          helpers._check_command_response(result, self.close)
  
          # write commands - skip getLastError checking
          if is_command:
              return result
  
          # getLastError
          error_msg = result.get("err", "")
          if error_msg is None:
              return result
          if error_msg.startswith("not master"):
              self.close()
              raise AutoReconnect(error_msg)
  
          details = result
          # mongos returns the error code in an error object
          # for some errors.
          if "errObjects" in result:
              for errobj in result["errObjects"]:
                  if errobj.get("err") == error_msg:
                      details = errobj
                      break
  
          code = details.get("code")
          if code in (11000, 11001, 12582):
              raise DuplicateKeyError(details["err"], code, result)
          raise OperationFailure(details["err"], code, result)
  
      def __check_bson_size(self, message):
          """Make sure the message doesn't include BSON documents larger
          than the connected server will accept.
  
          :Parameters:
            - `message`: message to check
          """
          if len(message) == 3:
              (request_id, data, max_doc_size) = message
              if max_doc_size > self.max_bson_size:
                  raise DocumentTooLarge("BSON document too large (%d bytes)"
                                         " - the connected server supports"
                                         " BSON document sizes up to %d"
                                         " bytes." %
                                         (max_doc_size, self.max_bson_size))
              return (request_id, data)
          else:
              # get_more and kill_cursors messages
              # don't include BSON documents.
              return message
  
      def _send_message(self, message,
                        with_last_error=False, command=False):
          """Say something to Mongo.
  
          Raises ConnectionFailure if the message cannot be sent. Raises
          OperationFailure if `with_last_error` is ``True`` and the
          response to the getLastError call returns an error. Return the
          response from lastError, or ``None`` if `with_last_error`
          is ``False``.
  
          :Parameters:
            - `message`: message to send
            - `with_last_error`: check getLastError status after sending the
              message
          """
          member = self.__ensure_member()
          if not with_last_error and not self.is_primary:
              # The write won't succeed, bail as if we'd done a getLastError
              raise AutoReconnect("not master")
  
          sock_info = self.__socket(member)
          try:
              try:
                  (request_id, data) = self.__check_bson_size(message)
                  sock_info.sock.sendall(data)
                  # Safe mode. We pack the message together with a lastError
                  # message and send both. We then get the response (to the
                  # lastError) and raise OperationFailure if it is an error
                  # response.
                  rv = None
                  if with_last_error:
                      response = self.__receive_message_on_socket(1, request_id,
                                                                  sock_info)
                      rv = self.__check_response_to_last_error(response, command)
  
                  return rv
              except OperationFailure:
                  raise
              except (ConnectionFailure, socket.error), e:
                  self.close()
                  raise AutoReconnect(str(e))
              except:
                  sock_info.close()
                  raise
          finally:
              member.maybe_return_socket(sock_info)
  
      def __receive_data_on_socket(self, length, sock_info):
          """Lowest level receive operation.
  
          Takes length to receive and repeatedly calls recv until able to
          return a buffer of that length, raising ConnectionFailure on error.
          """
          message = EMPTY
          while length:
              chunk = sock_info.sock.recv(length)
              if chunk == EMPTY:
                  raise ConnectionFailure("connection closed")
              length -= len(chunk)
              message += chunk
          return message
  
      def __receive_message_on_socket(self, operation, rqst_id, sock_info):
          """Receive a message in response to `rqst_id` on `sock`.
  
          Returns the response data with the header removed.
          """
          header = self.__receive_data_on_socket(16, sock_info)
          length = struct.unpack("<i", header[:4])[0]
  
          actual_op = struct.unpack("<i", header[12:])[0]
          assert actual_op == operation, (
              "wire protocol error: unknown opcode %r" % (actual_op,))
  
          # No rqst_id for exhaust cursor "getMore".
          if rqst_id is not None:
              resp_id = struct.unpack("<i", header[8:12])[0]
              assert rqst_id == resp_id, (
                  "wire protocol error: got response id %r but expected %r"
                  % (resp_id, rqst_id))
  
          assert length > 16, ("wire protocol error: message length is shorter"
                               " than standard message header: %r" % (length,))
  
          return self.__receive_data_on_socket(length - 16, sock_info)
  
      def __send_and_receive(self, message, sock_info):
          """Send a message on the given socket and return the response data.
          """
          (request_id, data) = self.__check_bson_size(message)
          try:
              sock_info.sock.sendall(data)
              return self.__receive_message_on_socket(1, request_id, sock_info)
          except:
              sock_info.close()
              raise
  
      # we just ignore _must_use_master here: it's only relevant for
      # MasterSlaveConnection instances.
      def _send_message_with_response(self, message,
                                      _must_use_master=False, **kwargs):
          """Send a message to Mongo and return the response.
  
          Sends the given message and returns the response.
  
          :Parameters:
            - `message`: (request_id, data) pair making up the message to send
          """
          member = self.__ensure_member()
          sock_info = self.__socket(member)
          exhaust = kwargs.get('exhaust')
          try:
              if not exhaust and "network_timeout" in kwargs:
                  sock_info.sock.settimeout(kwargs["network_timeout"])
  
              response = self.__send_and_receive(message, sock_info)
  
              if not exhaust:
                  if "network_timeout" in kwargs:
                      sock_info.sock.settimeout(self.__net_timeout)
  
                  member.maybe_return_socket(sock_info)
  
              return (None, (response, sock_info, member.pool))
          except (ConnectionFailure, socket.error), e:
              self.close()
              member.maybe_return_socket(sock_info)
              raise AutoReconnect(str(e))
          except:
              member.maybe_return_socket(sock_info)
              raise
  
      def _exhaust_next(self, sock_info):
          """Used with exhaust cursors to get the next batch off the socket.
  
          Can raise AutoReconnect.
          """
          try:
              return self.__receive_message_on_socket(1, None, sock_info)
          except socket.error, e:
              raise AutoReconnect(str(e))
  
      def start_request(self):
          """**DEPRECATED**: start_request is removed in PyMongo 3.0.
  
          When doing w=0 writes to MongoDB 2.4 or earlier, :meth:`start_request`
          was sometimes useful to ensure the current thread always used the same
          socket until it called :meth:`end_request`. This made consistent reads
          more likely after an unacknowledged write. Requests are no longer
          useful in modern MongoDB applications, see
          `PYTHON-785 <https://jira.mongodb.org/browse/PYTHON-785>`_.
  
          .. warning:: :meth:`start_request`, :meth:`in_request`,
            and :meth:`end_request` are deprecated, and removed in PyMongo 3.
            See the :doc:`/migrate-to-pymongo3` for more information.
  
          .. versionchanged:: 2.8
             Deprecated start_request.
  
          .. versionchanged:: 2.4
             Now counts the number of calls to start_request and doesn't end
             request until an equal number of calls to end_request.
  
          .. versionadded:: 2.2
             The :class:`~pymongo.pool.Request` return value.
             :meth:`start_request` previously returned None
          """
          member = self.__ensure_member()
          member.start_request()
          return pool.Request(self)
  
      def in_request(self):
          """**DEPRECATED**: True if this thread is in a request, meaning it has
          a socket reserved for its exclusive use.
  
          .. warning:: :meth:`start_request`, :meth:`in_request`,
            and :meth:`end_request` are deprecated in this version of PyMongo and
            removed in PyMongo 3. See the :doc:`/migrate-to-pymongo3` for more
            information.
  
          .. versionchanged:: 2.8
            Deprecated in_request.
          """
          member = self.__member  # Don't try to connect if disconnected.
          return member and member.in_request()
  
      def end_request(self):
          """**DEPRECATED**: Undo :meth:`start_request`. If :meth:`end_request`
          is called as many times as :meth:`start_request`, the request is over
          and this thread's connection returns to the pool. Extra calls to
          :meth:`end_request` have no effect.
  
          Ending a request allows the :class:`~socket.socket` that has
          been reserved for this thread by :meth:`start_request` to be returned to
          the pool. Other threads will then be able to re-use that
          :class:`~socket.socket`. If your application uses many threads, or has
          long-running threads that infrequently perform MongoDB operations, then
          judicious use of this method can lead to performance gains. Care should
          be taken, however, to make sure that :meth:`end_request` is not called
          in the middle of a sequence of operations in which ordering is
          important. This could lead to unexpected results.
  
          .. warning:: :meth:`start_request`, :meth:`in_request`,
            and :meth:`end_request` are deprecated in this version of PyMongo and
            removed in PyMongo 3. See the :doc:`/migrate-to-pymongo3` for more
            information.
  
          .. versionchanged:: 2.8
            Deprecated end_request.
          """
          member = self.__member  # Don't try to connect if disconnected.
          if member:
              member.end_request()
  
      def __eq__(self, other):
          if isinstance(other, self.__class__):
              return self.address == other.address
          return NotImplemented
  
      def __ne__(self, other):
          return not self == other
  
      def __repr__(self):
          if len(self.__nodes) == 1:
              return "MongoClient(%r, %r)" % self.address
          else:
              return "MongoClient(%r)" % ["%s:%d" % n for n in self.__nodes]
  
      def __getattr__(self, name):
          """Get a database by name.
  
          Raises :class:`~pymongo.errors.InvalidName` if an invalid
          database name is used.
  
          :Parameters:
            - `name`: the name of the database to get
          """
          return database.Database(self, name)
  
      def __getitem__(self, name):
          """Get a database by name.
  
          Raises :class:`~pymongo.errors.InvalidName` if an invalid
          database name is used.
  
          :Parameters:
            - `name`: the name of the database to get
          """
          return self.__getattr__(name)
  
      def close_cursor(self, cursor_id):
          """Close a single database cursor.
  
          Raises :class:`TypeError` if `cursor_id` is not an instance of
          ``(int, long)``. What closing the cursor actually means
          depends on this client's cursor manager.
  
          :Parameters:
            - `cursor_id`: id of cursor to close
          """
          if not isinstance(cursor_id, (int, long)):
              raise TypeError("cursor_id must be an instance of (int, long)")
  
          self.__cursor_manager.close(cursor_id)
  
      def kill_cursors(self, cursor_ids):
          """Send a kill cursors message with the given ids.
  
          Raises :class:`TypeError` if `cursor_ids` is not an instance of
          ``list``.
  
          :Parameters:
            - `cursor_ids`: list of cursor ids to kill
          """
          if not isinstance(cursor_ids, list):
              raise TypeError("cursor_ids must be a list")
  
          member = self.__member
  
          # We can't risk taking the lock to reconnect if we're being called
          # from Cursor.__del__, see PYTHON-799.
          if not member:
              warnings.warn("not connected, couldn't close cursor")
              return
  
          _, kill_cursors_msg = message.kill_cursors(cursor_ids)
          sock_info = self.__socket(member)
          try:
              try:
                  sock_info.sock.sendall(kill_cursors_msg)
              except:
                  sock_info.close()
                  raise
          finally:
              member.maybe_return_socket(sock_info)
  
      def server_info(self):
          """Get information about the MongoDB server we're connected to.
          """
          return self.admin.command("buildinfo",
                                    read_preference=ReadPreference.PRIMARY)
  
      def database_names(self):
          """Get a list of the names of all databases on the connected server.
          """
          # SERVER-15994 changed listDatabases to require slaveOk when run
          # against a secondary / slave. Passing slave_okay=True makes things
          # consistent across server versions.
          return [db["name"] for db in
                  self.admin.command(
                      "listDatabases",
                      read_preference=ReadPreference.PRIMARY,
                      slave_okay=not self.is_mongos)["databases"]]
  
      def drop_database(self, name_or_database):
          """Drop a database.
  
          Raises :class:`TypeError` if `name_or_database` is not an instance of
          :class:`basestring` (:class:`str` in python 3) or Database.
  
          :Parameters:
            - `name_or_database`: the name of a database to drop, or a
              :class:`~pymongo.database.Database` instance representing the
              database to drop
          """
          name = name_or_database
          if isinstance(name, database.Database):
              name = name.name
  
          if not isinstance(name, basestring):
              raise TypeError("name_or_database must be an instance of "
                              "%s or Database" % (basestring.__name__,))
  
          self._purge_index(name)
          self[name].command("dropDatabase",
                             read_preference=ReadPreference.PRIMARY)
  
      def copy_database(self, from_name, to_name,
                        from_host=None, username=None, password=None,
                        mechanism='DEFAULT'):
          """**DEPRECATED**: Copy a database, potentially from another host.
  
          Raises :class:`TypeError` if `from_name` or `to_name` is not
          an instance of :class:`basestring` (:class:`str` in python 3).
          Raises :class:`~pymongo.errors.InvalidName` if `to_name` is
          not a valid database name.
  
          If `from_host` is ``None`` the current host is used as the
          source. Otherwise the database is copied from `from_host`.
  
          If the source database requires authentication, `username` and
          `password` must be specified. By default, use SCRAM-SHA-1 with
          MongoDB 3.0 and later, MONGODB-CR (MongoDB Challenge Response
          protocol) for older servers.
  
          .. note:: mongos does not support copying a database from a server
             with authentication, see
             `SERVER-6427 <https://jira.mongodb.org/browse/SERVER-6427>`_.
  
          .. warning:: :meth:`copy_database` is removed in PyMongo 3.0. See the
            :doc:`copy_database examples </examples/copydb>` for alternatives.
  
          :Parameters:
            - `from_name`: the name of the source database
            - `to_name`: the name of the target database
            - `from_host` (optional): host name to copy from
            - `username` (optional): username for source database
            - `password` (optional): password for source database
            - `mechanism` (optional): auth method, 'MONGODB-CR' or 'SCRAM-SHA-1'
  
          .. versionchanged:: 2.8
             Deprecated copy_database, and added SCRAM-SHA-1 support.
          """
          member = self.__ensure_member()
          sock_info = self.__socket(member)
          try:
              helpers._copy_database(
                  fromdb=from_name,
                  todb=to_name,
                  fromhost=from_host,
                  mechanism=mechanism,
                  username=username,
                  password=password,
                  sock_info=sock_info,
                  cmd_func=self.__simple_command)
          finally:
              member.pool.maybe_return_socket(sock_info)
  
      def get_default_database(self):
          """Get the database named in the MongoDB connection URI.
  
          >>> uri = 'mongodb://host/my_database'
          >>> client = MongoClient(uri)
          >>> db = client.get_default_database()
          >>> assert db.name == 'my_database'
  
          Useful in scripts where you want to choose which database to use
          based only on the URI in a configuration file.
          """
          if self.__default_database_name is None:
              raise ConfigurationError('No default database defined')
  
          return self[self.__default_database_name]
  
      def get_database(self, name, codec_options=None,
                       read_preference=None, write_concern=None):
          """Get a :class:`~pymongo.database.Database` with the given name and
          options.
  
          Useful for creating a :class:`~pymongo.database.Database` with
          different codec options, read preference, and/or write concern from
          this :class:`MongoClient`.
  
            >>> from pymongo import ReadPreference
            >>> client.read_preference == ReadPreference.PRIMARY
            True
            >>> db1 = client.test
            >>> db1.read_preference == ReadPreference.PRIMARY
            True
            >>> db2 = client.get_database(
            ...     'test', read_preference=ReadPreference.SECONDARY)
            >>> db2.read_preference == ReadPreference.SECONDARY
            True
  
          :Parameters:
            - `name`: The name of the database - a string.
            - `codec_options` (optional): An instance of
              :class:`~bson.codec_options.CodecOptions`. If ``None`` (the
              default) the :attr:`codec_options` of this :class:`MongoClient` is
              used.
            - `read_preference` (optional): The read preference to use. If
              ``None`` (the default) the :attr:`read_preference` of this
              :class:`MongoClient` is used. See :mod:`~pymongo.read_preferences`
              for options.
            - `write_concern` (optional): An instance of
              :class:`~pymongo.write_concern.WriteConcern`. If ``None`` (the
              default) the :attr:`write_concern` of this :class:`MongoClient` is
              used.
  
          .. versionadded:: 2.9
          """
          return database.Database(
              self, name, codec_options, read_preference, write_concern)
  
      @property
      def is_locked(self):
          """Is this server locked? While locked, all write operations
          are blocked, although read operations may still be allowed.
          Use :meth:`unlock` to unlock.
  
          .. versionadded:: 2.0
          """
          ops = self.admin.current_op()
          return bool(ops.get('fsyncLock', 0))
  
      def fsync(self, **kwargs):
          """Flush all pending writes to datafiles.
  
          :Parameters:
  
              Optional parameters can be passed as keyword arguments:
  
              - `lock`: If True lock the server to disallow writes.
              - `async`: If True don't block while synchronizing.
  
              .. warning:: `async` and `lock` can not be used together.
  
              .. warning:: MongoDB does not support the `async` option
                           on Windows and will raise an exception on that
                           platform.
  
          .. versionadded:: 2.0
          """
          self.admin.command("fsync",
                             read_preference=ReadPreference.PRIMARY, **kwargs)
  
      def unlock(self):
          """Unlock a previously locked server.
  
          .. versionadded:: 2.0
          """
          self.admin['$cmd'].sys.unlock.find_one()
  
      def __enter__(self):
          return self
  
      def __exit__(self, exc_type, exc_val, exc_tb):
          self.close()
  
      def __iter__(self):
          return self
  
      def next(self):
          raise TypeError("'MongoClient' object is not iterable")
  