PYTHON-1104 Change server-selector signature.

Preparation for maxStalenessMS implementation: selectors now take a
TopologyDescription, not a list of ServerDescriptions.

Author: ajdavis

pymongo/read_preferences.py

@@ -151,9 +151,9 @@ class Primary(_ServerMode):
     def __init__(self):
         super(Primary, self).__init__(_PRIMARY)
 
-    def __call__(self, server_descriptions):
-        """Return matching ServerDescriptions from a list."""
-        return writable_server_selector(server_descriptions)
+    def __call__(self, td):
+        """Return matching ServerDescriptions from a TopologyDescription."""
+        return writable_server_selector(td)
 
     def __repr__(self):
         return "Primary()"
@@ -182,15 +182,13 @@ class PrimaryPreferred(_ServerMode):
     def __init__(self, tag_sets=None):
         super(PrimaryPreferred, self).__init__(_PRIMARY_PREFERRED, tag_sets)
 
-    def __call__(self, server_descriptions):
-        """Return matching ServerDescriptions from a list."""
-        writable_servers = writable_server_selector(server_descriptions)
+    def __call__(self, td):
+        """Return matching ServerDescriptions from a TopologyDescription."""
+        writable_servers = writable_server_selector(td)
         if writable_servers:
             return writable_servers
         else:
-            return secondary_with_tags_server_selector(
-                self.tag_sets,
-                server_descriptions)
+            return secondary_with_tags_server_selector(self.tag_sets, td)
 
 
 class Secondary(_ServerMode):
@@ -210,11 +208,9 @@ class Secondary(_ServerMode):
     def __init__(self, tag_sets=None):
         super(Secondary, self).__init__(_SECONDARY, tag_sets)
 
-    def __call__(self, server_descriptions):
-        """Return matching ServerDescriptions from a list."""
-        return secondary_with_tags_server_selector(
-            self.tag_sets,
-            server_descriptions)
+    def __call__(self, td):
+        """Return matching ServerDescriptions from a TopologyDescription."""
+        return secondary_with_tags_server_selector(self.tag_sets, td)
 
 
 class SecondaryPreferred(_ServerMode):
@@ -234,16 +230,14 @@ class SecondaryPreferred(_ServerMode):
     def __init__(self, tag_sets=None):
         super(SecondaryPreferred, self).__init__(_SECONDARY_PREFERRED, tag_sets)
 
-    def __call__(self, server_descriptions):
-        """Return matching ServerDescriptions from a list."""
-        secondaries = secondary_with_tags_server_selector(
-            self.tag_sets,
-            server_descriptions)
+    def __call__(self, td):
+        """Return matching ServerDescriptions from a TopologyDescription."""
+        secondaries = secondary_with_tags_server_selector(self.tag_sets, td)
 
         if secondaries:
             return secondaries
         else:
-            return writable_server_selector(server_descriptions)
+            return writable_server_selector(td)
 
 
 class Nearest(_ServerMode):
@@ -263,11 +257,9 @@ class Nearest(_ServerMode):
     def __init__(self, tag_sets=None):
         super(Nearest, self).__init__(_NEAREST, tag_sets)
 
-    def __call__(self, server_descriptions):
-        """Return matching ServerDescriptions from a list."""
-        return member_with_tags_server_selector(
-            self.tag_sets or [{}],
-            server_descriptions)
+    def __call__(self, td):
+        """Return matching ServerDescriptions from a TopologyDescription."""
+        return member_with_tags_server_selector(self.tag_sets or [{}], td)
 
 
 _ALL_READ_PREFERENCES = (Primary, PrimaryPreferred,

pymongo/server_selectors.py

@@ -12,41 +12,39 @@
 # implied.  See the License for the specific language governing
 # permissions and limitations under the License.
 
-"""Criteria to select some ServerDescriptions out of a list."""
+"""Criteria to select some ServerDescriptions from a TopologyDescription."""
 
 from pymongo.server_type import SERVER_TYPE
 
 
-def any_server_selector(server_descriptions):
-    return server_descriptions
+def any_server_selector(td):
+    return td.known_servers
 
 
-def readable_server_selector(server_descriptions):
-    return [s for s in server_descriptions if s.is_readable]
+def readable_server_selector(td):
+    return [s for s in td.known_servers if s.is_readable]
 
 
-def writable_server_selector(server_descriptions):
-    return [s for s in server_descriptions if s.is_writable]
+def writable_server_selector(td):
+    return [s for s in td.known_servers if s.is_writable]
 
 
-def secondary_server_selector(server_descriptions):
-    return [s for s in server_descriptions
+def secondary_server_selector(td):
+    return [s for s in td.known_servers
             if s.server_type == SERVER_TYPE.RSSecondary]
 
 
-def arbiter_server_selector(server_descriptions):
-    return [s for s in server_descriptions
+def arbiter_server_selector(td):
+    return [s for s in td.known_servers
             if s.server_type == SERVER_TYPE.RSArbiter]
 
 
-def writable_preferred_server_selector(server_descriptions):
+def writable_preferred_server_selector(td):
     """Like PrimaryPreferred but doesn't use tags or latency."""
-    return (
-        writable_server_selector(server_descriptions) or
-        secondary_server_selector(server_descriptions))
+    return writable_server_selector(td) or secondary_server_selector(td)
 
 
-def single_tag_set_server_selector(tag_set, server_descriptions):
+def apply_single_tag_set(tag_set, server_descriptions):
     """All servers matching one tag set.
 
     A tag set is a dict. A server matches if its tags are a superset:
@@ -69,7 +67,7 @@ def tags_match(server_tags):
     return [s for s in server_descriptions if tags_match(s.tags)]
 
 
-def tag_sets_server_selector(tag_sets, server_descriptions):
+def apply_tag_sets(tag_sets, server_descriptions):
     """All servers match a list of tag sets.
 
     tag_sets is a list of dicts. The empty tag set {} matches any server,
@@ -84,7 +82,7 @@ def tag_sets_server_selector(tag_sets, server_descriptions):
     first.
     """
     for tag_set in tag_sets:
-        selected = single_tag_set_server_selector(tag_set, server_descriptions)
+        selected = apply_single_tag_set(tag_set, server_descriptions)
         if selected:
             return selected
 
@@ -115,13 +113,11 @@ def apply_local_threshold(latency_ms, server_descriptions):
         if (s.round_trip_time - fastest) <= latency_ms / 1000.]
 
 
-def secondary_with_tags_server_selector(tag_sets, server_descriptions):
+def secondary_with_tags_server_selector(tag_sets, td):
     """All near-enough secondaries matching the tag sets."""
-    return tag_sets_server_selector(
-        tag_sets, secondary_server_selector(server_descriptions))
+    return apply_tag_sets(tag_sets, secondary_server_selector(td))
 
 
-def member_with_tags_server_selector(tag_sets, server_descriptions):
+def member_with_tags_server_selector(tag_sets, td):
     """All near-enough members matching the tag sets."""
-    return tag_sets_server_selector(
-        tag_sets, readable_server_selector(server_descriptions))
+    return apply_tag_sets(tag_sets, readable_server_selector(td))

pymongo/topology.py

@@ -284,9 +284,7 @@ def get_primary(self):
             if topology_type != TOPOLOGY_TYPE.ReplicaSetWithPrimary:
                 return None
 
-            description = writable_server_selector(
-                self._description.known_servers)[0]
-
+            description = writable_server_selector(self._description)[0]
             return description.address
 
     def _get_replica_set_members(self, selector):
@@ -298,7 +296,7 @@ def _get_replica_set_members(self, selector):
                                      TOPOLOGY_TYPE.ReplicaSetNoPrimary):
                 return set()
 
-            descriptions = selector(self._description.known_servers)
+            descriptions = selector(self._description)
             return set([d.address for d in descriptions])
 
     def get_secondaries(self):
@@ -417,7 +415,7 @@ def _apply_selector(self, selector, address):
             return apply_local_threshold(self._settings.local_threshold_ms,
                                          self._description.known_servers)
         else:
-            sds = selector(self._description.known_servers)
+            sds = selector(self._description)
             return apply_local_threshold(
                 self._settings.local_threshold_ms, sds)