155 lines
5.0 KiB
Python
155 lines
5.0 KiB
Python
# Copyright 2014-2016 MongoDB, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you
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# may not use this file except in compliance with the License. You
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# may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied. See the License for the specific language governing
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# permissions and limitations under the License.
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"""Criteria to select some ServerDescriptions from a TopologyDescription."""
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from pymongo.server_type import SERVER_TYPE
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class Selection:
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"""Input or output of a server selector function."""
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@classmethod
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def from_topology_description(cls, topology_description):
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known_servers = topology_description.known_servers
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primary = None
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for sd in known_servers:
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if sd.server_type == SERVER_TYPE.RSPrimary:
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primary = sd
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break
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return Selection(
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topology_description,
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topology_description.known_servers,
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topology_description.common_wire_version,
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primary,
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)
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def __init__(self, topology_description, server_descriptions, common_wire_version, primary):
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self.topology_description = topology_description
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self.server_descriptions = server_descriptions
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self.primary = primary
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self.common_wire_version = common_wire_version
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def with_server_descriptions(self, server_descriptions):
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return Selection(
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self.topology_description, server_descriptions, self.common_wire_version, self.primary
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)
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def secondary_with_max_last_write_date(self):
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secondaries = secondary_server_selector(self)
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if secondaries.server_descriptions:
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return max(secondaries.server_descriptions, key=lambda sd: sd.last_write_date)
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return None
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@property
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def primary_selection(self):
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primaries = [self.primary] if self.primary else []
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return self.with_server_descriptions(primaries)
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@property
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def heartbeat_frequency(self):
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return self.topology_description.heartbeat_frequency
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@property
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def topology_type(self):
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return self.topology_description.topology_type
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def __bool__(self):
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return bool(self.server_descriptions)
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def __getitem__(self, item):
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return self.server_descriptions[item]
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def any_server_selector(selection):
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return selection
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def readable_server_selector(selection):
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return selection.with_server_descriptions(
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[s for s in selection.server_descriptions if s.is_readable]
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)
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def writable_server_selector(selection):
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return selection.with_server_descriptions(
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[s for s in selection.server_descriptions if s.is_writable]
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)
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def secondary_server_selector(selection):
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return selection.with_server_descriptions(
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[s for s in selection.server_descriptions if s.server_type == SERVER_TYPE.RSSecondary]
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)
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def arbiter_server_selector(selection):
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return selection.with_server_descriptions(
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[s for s in selection.server_descriptions if s.server_type == SERVER_TYPE.RSArbiter]
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)
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def writable_preferred_server_selector(selection):
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"""Like PrimaryPreferred but doesn't use tags or latency."""
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return writable_server_selector(selection) or secondary_server_selector(selection)
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def apply_single_tag_set(tag_set, selection):
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"""All servers matching one tag set.
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A tag set is a dict. A server matches if its tags are a superset:
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A server tagged {'a': '1', 'b': '2'} matches the tag set {'a': '1'}.
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The empty tag set {} matches any server.
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"""
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def tags_match(server_tags):
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for key, value in tag_set.items():
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if key not in server_tags or server_tags[key] != value:
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return False
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return True
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return selection.with_server_descriptions(
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[s for s in selection.server_descriptions if tags_match(s.tags)]
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)
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def apply_tag_sets(tag_sets, selection):
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"""All servers match a list of tag sets.
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tag_sets is a list of dicts. The empty tag set {} matches any server,
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and may be provided at the end of the list as a fallback. So
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[{'a': 'value'}, {}] expresses a preference for servers tagged
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{'a': 'value'}, but accepts any server if none matches the first
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preference.
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"""
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for tag_set in tag_sets:
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with_tag_set = apply_single_tag_set(tag_set, selection)
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if with_tag_set:
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return with_tag_set
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return selection.with_server_descriptions([])
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def secondary_with_tags_server_selector(tag_sets, selection):
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"""All near-enough secondaries matching the tag sets."""
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return apply_tag_sets(tag_sets, secondary_server_selector(selection))
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def member_with_tags_server_selector(tag_sets, selection):
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"""All near-enough members matching the tag sets."""
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return apply_tag_sets(tag_sets, readable_server_selector(selection))
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