/usr/lib/python3/dist-packages/pymongo/topology_description.py is in python3-pymongo 3.6.1+dfsg1-1.
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#
# 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
TOPOLOGY_TYPE = namedtuple('TopologyType', ['Single', 'ReplicaSetNoPrimary',
'ReplicaSetWithPrimary', 'Sharded',
'Unknown'])(*range(5))
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."""
return updated_topology_description(self, ServerDescription(address))
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):
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 the selector.
return self.known_servers
elif address:
description = self.server_descriptions().get(address)
return [description] if description else []
elif self.topology_type == TOPOLOGY_TYPE.Sharded:
# Ignore the read preference, but apply localThresholdMS.
return apply_local_threshold(
Selection.from_topology_description(self))
else:
return apply_local_threshold(
selector(Selection.from_topology_description(self)))
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)
# 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:
# 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:
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 _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.
address = server_description.address
sds[address] = ServerDescription(address)
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] = ServerDescription(server.address)
# 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
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