# Copyright 2014-present 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. """Represent a deployment of MongoDB servers.""" from collections import namedtuple from pymongo import common from pymongo.errors import ConfigurationError from pymongo.read_preferences import ReadPreference from pymongo.server_description import ServerDescription from pymongo.server_selectors import Selection from pymongo.server_type import SERVER_TYPE # Enumeration for various kinds of MongoDB cluster topologies. TOPOLOGY_TYPE = namedtuple('TopologyType', ['Single', 'ReplicaSetNoPrimary', 'ReplicaSetWithPrimary', 'Sharded', 'Unknown'])(*range(5)) # Topologies compatible with SRV record polling. SRV_POLLING_TOPOLOGIES = (TOPOLOGY_TYPE.Unknown, TOPOLOGY_TYPE.Sharded) class TopologyDescription(object): def __init__(self, topology_type, server_descriptions, replica_set_name, max_set_version, max_election_id, topology_settings): """Representation of a deployment of MongoDB servers. :Parameters: - `topology_type`: initial type - `server_descriptions`: dict of (address, ServerDescription) for all seeds - `replica_set_name`: replica set name or None - `max_set_version`: greatest setVersion seen from a primary, or None - `max_election_id`: greatest electionId seen from a primary, or None - `topology_settings`: a TopologySettings """ self._topology_type = topology_type self._replica_set_name = replica_set_name self._server_descriptions = server_descriptions self._max_set_version = max_set_version self._max_election_id = max_election_id # The heartbeat_frequency is used in staleness estimates. self._topology_settings = topology_settings # Is PyMongo compatible with all servers' wire protocols? self._incompatible_err = None for s in self._server_descriptions.values(): if not s.is_server_type_known: continue # s.min/max_wire_version is the server's wire protocol. # MIN/MAX_SUPPORTED_WIRE_VERSION is what PyMongo supports. server_too_new = ( # Server too new. s.min_wire_version is not None and s.min_wire_version > common.MAX_SUPPORTED_WIRE_VERSION) server_too_old = ( # Server too old. s.max_wire_version is not None and s.max_wire_version < common.MIN_SUPPORTED_WIRE_VERSION) if server_too_new: self._incompatible_err = ( "Server at %s:%d requires wire version %d, but this " "version of PyMongo only supports up to %d." % (s.address[0], s.address[1], s.min_wire_version, common.MAX_SUPPORTED_WIRE_VERSION)) elif server_too_old: self._incompatible_err = ( "Server at %s:%d reports wire version %d, but this " "version of PyMongo requires at least %d (MongoDB %s)." % (s.address[0], s.address[1], s.max_wire_version, common.MIN_SUPPORTED_WIRE_VERSION, common.MIN_SUPPORTED_SERVER_VERSION)) break # Server Discovery And Monitoring Spec: Whenever a client updates the # TopologyDescription from an ismaster response, it MUST set # TopologyDescription.logicalSessionTimeoutMinutes to the smallest # logicalSessionTimeoutMinutes value among ServerDescriptions of all # data-bearing server types. If any have a null # logicalSessionTimeoutMinutes, then # TopologyDescription.logicalSessionTimeoutMinutes MUST be set to null. readable_servers = self.readable_servers if not readable_servers: self._ls_timeout_minutes = None elif any(s.logical_session_timeout_minutes is None for s in readable_servers): self._ls_timeout_minutes = None else: self._ls_timeout_minutes = min(s.logical_session_timeout_minutes for s in readable_servers) def check_compatible(self): """Raise ConfigurationError if any server is incompatible. A server is incompatible if its wire protocol version range does not overlap with PyMongo's. """ if self._incompatible_err: raise ConfigurationError(self._incompatible_err) def has_server(self, address): return address in self._server_descriptions def reset_server(self, address): """A copy of this description, with one server marked Unknown.""" unknown_sd = self._server_descriptions[address].to_unknown() return updated_topology_description(self, unknown_sd) def reset(self): """A copy of this description, with all servers marked Unknown.""" if self._topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary: topology_type = TOPOLOGY_TYPE.ReplicaSetNoPrimary else: topology_type = self._topology_type # The default ServerDescription's type is Unknown. sds = dict((address, ServerDescription(address)) for address in self._server_descriptions) return TopologyDescription( topology_type, sds, self._replica_set_name, self._max_set_version, self._max_election_id, self._topology_settings) def server_descriptions(self): """Dict of (address, :class:`~pymongo.server_description.ServerDescription`).""" return self._server_descriptions.copy() @property def topology_type(self): """The type of this topology.""" return self._topology_type @property def topology_type_name(self): """The topology type as a human readable string. .. versionadded:: 3.4 """ return TOPOLOGY_TYPE._fields[self._topology_type] @property def replica_set_name(self): """The replica set name.""" return self._replica_set_name @property def max_set_version(self): """Greatest setVersion seen from a primary, or None.""" return self._max_set_version @property def max_election_id(self): """Greatest electionId seen from a primary, or None.""" return self._max_election_id @property def logical_session_timeout_minutes(self): """Minimum logical session timeout, or None.""" return self._ls_timeout_minutes @property def known_servers(self): """List of Servers of types besides Unknown.""" return [s for s in self._server_descriptions.values() if s.is_server_type_known] @property def has_known_servers(self): """Whether there are any Servers of types besides Unknown.""" return any(s for s in self._server_descriptions.values() if s.is_server_type_known) @property def readable_servers(self): """List of readable Servers.""" return [s for s in self._server_descriptions.values() if s.is_readable] @property def common_wire_version(self): """Minimum of all servers' max wire versions, or None.""" servers = self.known_servers if servers: return min(s.max_wire_version for s in self.known_servers) return None @property def heartbeat_frequency(self): return self._topology_settings.heartbeat_frequency def apply_selector(self, selector, address, custom_selector=None): def apply_local_threshold(selection): if not selection: return [] settings = self._topology_settings # Round trip time in seconds. fastest = min( s.round_trip_time for s in selection.server_descriptions) threshold = settings.local_threshold_ms / 1000.0 return [s for s in selection.server_descriptions if (s.round_trip_time - fastest) <= threshold] if getattr(selector, 'min_wire_version', 0): common_wv = self.common_wire_version if common_wv and common_wv < selector.min_wire_version: raise ConfigurationError( "%s requires min wire version %d, but topology's min" " wire version is %d" % (selector, selector.min_wire_version, common_wv)) if self.topology_type == TOPOLOGY_TYPE.Single: # Ignore selectors for standalone. return self.known_servers elif address: # Ignore selectors when explicit address is requested. description = self.server_descriptions().get(address) return [description] if description else [] elif self.topology_type == TOPOLOGY_TYPE.Sharded: # Ignore read preference. selection = Selection.from_topology_description(self) else: selection = selector(Selection.from_topology_description(self)) # Apply custom selector followed by localThresholdMS. if custom_selector is not None and selection: selection = selection.with_server_descriptions( custom_selector(selection.server_descriptions)) return apply_local_threshold(selection) def has_readable_server(self, read_preference=ReadPreference.PRIMARY): """Does this topology have any readable servers available matching the given read preference? :Parameters: - `read_preference`: an instance of a read preference from :mod:`~pymongo.read_preferences`. Defaults to :attr:`~pymongo.read_preferences.ReadPreference.PRIMARY`. .. note:: When connected directly to a single server this method always returns ``True``. .. versionadded:: 3.4 """ common.validate_read_preference("read_preference", read_preference) return any(self.apply_selector(read_preference, None)) def has_writable_server(self): """Does this topology have a writable server available? .. note:: When connected directly to a single server this method always returns ``True``. .. versionadded:: 3.4 """ return self.has_readable_server(ReadPreference.PRIMARY) def __repr__(self): # Sort the servers by address. servers = sorted(self._server_descriptions.values(), key=lambda sd: sd.address) return "<%s id: %s, topology_type: %s, servers: %r>" % ( self.__class__.__name__, self._topology_settings._topology_id, self.topology_type_name, servers) # If topology type is Unknown and we receive an ismaster response, what should # the new topology type be? _SERVER_TYPE_TO_TOPOLOGY_TYPE = { SERVER_TYPE.Mongos: TOPOLOGY_TYPE.Sharded, SERVER_TYPE.RSPrimary: TOPOLOGY_TYPE.ReplicaSetWithPrimary, SERVER_TYPE.RSSecondary: TOPOLOGY_TYPE.ReplicaSetNoPrimary, SERVER_TYPE.RSArbiter: TOPOLOGY_TYPE.ReplicaSetNoPrimary, SERVER_TYPE.RSOther: TOPOLOGY_TYPE.ReplicaSetNoPrimary, } def updated_topology_description(topology_description, server_description): """Return an updated copy of a TopologyDescription. :Parameters: - `topology_description`: the current TopologyDescription - `server_description`: a new ServerDescription that resulted from an ismaster call Called after attempting (successfully or not) to call ismaster on the server at server_description.address. Does not modify topology_description. """ address = server_description.address # These values will be updated, if necessary, to form the new # TopologyDescription. topology_type = topology_description.topology_type set_name = topology_description.replica_set_name max_set_version = topology_description.max_set_version max_election_id = topology_description.max_election_id server_type = server_description.server_type # Don't mutate the original dict of server descriptions; copy it. sds = topology_description.server_descriptions() # Replace this server's description with the new one. sds[address] = server_description if topology_type == TOPOLOGY_TYPE.Single: # Set server type to Unknown if replica set name does not match. if (set_name is not None and set_name != server_description.replica_set_name): error = ConfigurationError( "client is configured to connect to a replica set named " "'%s' but this node belongs to a set named '%s'" % ( set_name, server_description.replica_set_name)) sds[address] = server_description.to_unknown(error=error) # Single type never changes. return TopologyDescription( TOPOLOGY_TYPE.Single, sds, set_name, max_set_version, max_election_id, topology_description._topology_settings) if topology_type == TOPOLOGY_TYPE.Unknown: if server_type == SERVER_TYPE.Standalone: if len(topology_description._topology_settings.seeds) == 1: topology_type = TOPOLOGY_TYPE.Single else: # Remove standalone from Topology when given multiple seeds. sds.pop(address) elif server_type not in (SERVER_TYPE.Unknown, SERVER_TYPE.RSGhost): topology_type = _SERVER_TYPE_TO_TOPOLOGY_TYPE[server_type] if topology_type == TOPOLOGY_TYPE.Sharded: if server_type not in (SERVER_TYPE.Mongos, SERVER_TYPE.Unknown): sds.pop(address) elif topology_type == TOPOLOGY_TYPE.ReplicaSetNoPrimary: if server_type in (SERVER_TYPE.Standalone, SERVER_TYPE.Mongos): sds.pop(address) elif server_type == SERVER_TYPE.RSPrimary: (topology_type, set_name, max_set_version, max_election_id) = _update_rs_from_primary(sds, set_name, server_description, max_set_version, max_election_id) elif server_type in ( SERVER_TYPE.RSSecondary, SERVER_TYPE.RSArbiter, SERVER_TYPE.RSOther): topology_type, set_name = _update_rs_no_primary_from_member( sds, set_name, server_description) elif topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary: if server_type in (SERVER_TYPE.Standalone, SERVER_TYPE.Mongos): sds.pop(address) topology_type = _check_has_primary(sds) elif server_type == SERVER_TYPE.RSPrimary: (topology_type, set_name, max_set_version, max_election_id) = _update_rs_from_primary(sds, set_name, server_description, max_set_version, max_election_id) elif server_type in ( SERVER_TYPE.RSSecondary, SERVER_TYPE.RSArbiter, SERVER_TYPE.RSOther): topology_type = _update_rs_with_primary_from_member( sds, set_name, server_description) else: # Server type is Unknown or RSGhost: did we just lose the primary? topology_type = _check_has_primary(sds) # Return updated copy. return TopologyDescription(topology_type, sds, set_name, max_set_version, max_election_id, topology_description._topology_settings) def _updated_topology_description_srv_polling(topology_description, seedlist): """Return an updated copy of a TopologyDescription. :Parameters: - `topology_description`: the current TopologyDescription - `seedlist`: a list of new seeds new ServerDescription that resulted from an ismaster call """ # Create a copy of the server descriptions. sds = topology_description.server_descriptions() # If seeds haven't changed, don't do anything. if set(sds.keys()) == set(seedlist): return topology_description # Add SDs corresponding to servers recently added to the SRV record. for address in seedlist: if address not in sds: sds[address] = ServerDescription(address) # Remove SDs corresponding to servers no longer part of the SRV record. for address in list(sds.keys()): if address not in seedlist: sds.pop(address) return TopologyDescription( topology_description.topology_type, sds, topology_description.replica_set_name, topology_description.max_set_version, topology_description.max_election_id, topology_description._topology_settings) def _update_rs_from_primary( sds, replica_set_name, server_description, max_set_version, max_election_id): """Update topology description from a primary's ismaster response. Pass in a dict of ServerDescriptions, current replica set name, the ServerDescription we are processing, and the TopologyDescription's max_set_version and max_election_id if any. Returns (new topology type, new replica_set_name, new max_set_version, new max_election_id). """ if replica_set_name is None: replica_set_name = server_description.replica_set_name elif replica_set_name != server_description.replica_set_name: # We found a primary but it doesn't have the replica_set_name # provided by the user. sds.pop(server_description.address) return (_check_has_primary(sds), replica_set_name, max_set_version, max_election_id) max_election_tuple = max_set_version, max_election_id if None not in server_description.election_tuple: if (None not in max_election_tuple and max_election_tuple > server_description.election_tuple): # Stale primary, set to type Unknown. sds[server_description.address] = server_description.to_unknown() return (_check_has_primary(sds), replica_set_name, max_set_version, max_election_id) max_election_id = server_description.election_id if (server_description.set_version is not None and (max_set_version is None or server_description.set_version > max_set_version)): max_set_version = server_description.set_version # We've heard from the primary. Is it the same primary as before? for server in sds.values(): if (server.server_type is SERVER_TYPE.RSPrimary and server.address != server_description.address): # Reset old primary's type to Unknown. sds[server.address] = server.to_unknown() # There can be only one prior primary. break # Discover new hosts from this primary's response. for new_address in server_description.all_hosts: if new_address not in sds: sds[new_address] = ServerDescription(new_address) # Remove hosts not in the response. for addr in set(sds) - server_description.all_hosts: sds.pop(addr) # If the host list differs from the seed list, we may not have a primary # after all. return (_check_has_primary(sds), replica_set_name, max_set_version, max_election_id) def _update_rs_with_primary_from_member( sds, replica_set_name, server_description): """RS with known primary. Process a response from a non-primary. Pass in a dict of ServerDescriptions, current replica set name, and the ServerDescription we are processing. Returns new topology type. """ assert replica_set_name is not None if replica_set_name != server_description.replica_set_name: sds.pop(server_description.address) elif (server_description.me and server_description.address != server_description.me): sds.pop(server_description.address) # Had this member been the primary? return _check_has_primary(sds) def _update_rs_no_primary_from_member( sds, replica_set_name, server_description): """RS without known primary. Update from a non-primary's response. Pass in a dict of ServerDescriptions, current replica set name, and the ServerDescription we are processing. Returns (new topology type, new replica_set_name). """ topology_type = TOPOLOGY_TYPE.ReplicaSetNoPrimary if replica_set_name is None: replica_set_name = server_description.replica_set_name elif replica_set_name != server_description.replica_set_name: sds.pop(server_description.address) return topology_type, replica_set_name # This isn't the primary's response, so don't remove any servers # it doesn't report. Only add new servers. for address in server_description.all_hosts: if address not in sds: sds[address] = ServerDescription(address) if (server_description.me and server_description.address != server_description.me): sds.pop(server_description.address) return topology_type, replica_set_name def _check_has_primary(sds): """Current topology type is ReplicaSetWithPrimary. Is primary still known? Pass in a dict of ServerDescriptions. Returns new topology type. """ for s in sds.values(): if s.server_type == SERVER_TYPE.RSPrimary: return TOPOLOGY_TYPE.ReplicaSetWithPrimary else: return TOPOLOGY_TYPE.ReplicaSetNoPrimary