Initial commit

venv/lib/python3.8/site-packages/pymongo/server_selectors.py

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+# Copyright 2014-2016 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.
+
+"""Criteria to select some ServerDescriptions from a TopologyDescription."""
+
+from pymongo.server_type import SERVER_TYPE
+
+
+class Selection(object):
+    """Input or output of a server selector function."""
+
+    @classmethod
+    def from_topology_description(cls, topology_description):
+        known_servers = topology_description.known_servers
+        primary = None
+        for sd in known_servers:
+            if sd.server_type == SERVER_TYPE.RSPrimary:
+                primary = sd
+                break
+
+        return Selection(topology_description,
+                         topology_description.known_servers,
+                         topology_description.common_wire_version,
+                         primary)
+
+    def __init__(self,
+                 topology_description,
+                 server_descriptions,
+                 common_wire_version,
+                 primary):
+        self.topology_description = topology_description
+        self.server_descriptions = server_descriptions
+        self.primary = primary
+        self.common_wire_version = common_wire_version
+
+    def with_server_descriptions(self, server_descriptions):
+        return Selection(self.topology_description,
+                         server_descriptions,
+                         self.common_wire_version,
+                         self.primary)
+
+    def secondary_with_max_last_write_date(self):
+        secondaries = secondary_server_selector(self)
+        if secondaries.server_descriptions:
+            return max(secondaries.server_descriptions,
+                       key=lambda sd: sd.last_write_date)
+
+    @property
+    def primary_selection(self):
+        primaries = [self.primary] if self.primary else []
+        return self.with_server_descriptions(primaries)
+
+    @property
+    def heartbeat_frequency(self):
+        return self.topology_description.heartbeat_frequency
+
+    @property
+    def topology_type(self):
+        return self.topology_description.topology_type
+
+    def __bool__(self):
+        return bool(self.server_descriptions)
+
+    __nonzero__ = __bool__  # Python 2.
+
+    def __getitem__(self, item):
+        return self.server_descriptions[item]
+
+
+def any_server_selector(selection):
+    return selection
+
+
+def readable_server_selector(selection):
+    return selection.with_server_descriptions(
+        [s for s in selection.server_descriptions if s.is_readable])
+
+
+def writable_server_selector(selection):
+    return selection.with_server_descriptions(
+        [s for s in selection.server_descriptions if s.is_writable])
+
+
+def secondary_server_selector(selection):
+    return selection.with_server_descriptions(
+        [s for s in selection.server_descriptions
+         if s.server_type == SERVER_TYPE.RSSecondary])
+
+
+def arbiter_server_selector(selection):
+    return selection.with_server_descriptions(
+        [s for s in selection.server_descriptions
+         if s.server_type == SERVER_TYPE.RSArbiter])
+
+
+def writable_preferred_server_selector(selection):
+    """Like PrimaryPreferred but doesn't use tags or latency."""
+    return (writable_server_selector(selection) or
+            secondary_server_selector(selection))
+
+
+def apply_single_tag_set(tag_set, selection):
+    """All servers matching one tag set.
+
+    A tag set is a dict. A server matches if its tags are a superset:
+    A server tagged {'a': '1', 'b': '2'} matches the tag set {'a': '1'}.
+
+    The empty tag set {} matches any server.
+    """
+    def tags_match(server_tags):
+        for key, value in tag_set.items():
+            if key not in server_tags or server_tags[key] != value:
+                return False
+
+        return True
+
+    return selection.with_server_descriptions(
+        [s for s in selection.server_descriptions if tags_match(s.tags)])
+
+
+def apply_tag_sets(tag_sets, selection):
+    """All servers match a list of tag sets.
+
+    tag_sets is a list of dicts. The empty tag set {} matches any server,
+    and may be provided at the end of the list as a fallback. So
+    [{'a': 'value'}, {}] expresses a preference for servers tagged
+    {'a': 'value'}, but accepts any server if none matches the first
+    preference.
+    """
+    for tag_set in tag_sets:
+        with_tag_set = apply_single_tag_set(tag_set, selection)
+        if with_tag_set:
+            return with_tag_set
+
+    return selection.with_server_descriptions([])
+
+
+def secondary_with_tags_server_selector(tag_sets, selection):
+    """All near-enough secondaries matching the tag sets."""
+    return apply_tag_sets(tag_sets, secondary_server_selector(selection))
+
+
+def member_with_tags_server_selector(tag_sets, selection):
+    """All near-enough members matching the tag sets."""
+    return apply_tag_sets(tag_sets, readable_server_selector(selection))