PYTHON-926 - ReadPreference.NEAREST shouldn't pick arbiters.

Author: behackett

pymongo/server_selectors.py

@@ -21,6 +21,10 @@ def any_server_selector(server_descriptions):
  return server_descriptions
 
 
+def readable_server_selector(server_descriptions):
+ return [s for s in server_descriptions if s.is_readable]
+
+
 def writable_server_selector(server_descriptions):
  return [s for s in server_descriptions if s.is_writable]
 
@@ -49,6 +53,11 @@ def single_tag_set_server_selector(tag_set, server_descriptions):
  A server tagged {'a': '1', 'b': '2'} matches the tag set {'a': '1'}.
 
  The empty tag set {} matches any server.
+
+ The `server_descriptions` passed to this function should have
+ non-readable servers (e.g. RSGhost, RSArbiter, Unknown) filtered
+ out (e.g. by readable_server_selector or secondary_server_selector)
+ first.
  """
  def tags_match(server_tags):
  for key, value in tag_set.items():
@@ -68,6 +77,11 @@ def tag_sets_server_selector(tag_sets, server_descriptions):
  [{'a': 'value'}, {}] expresses a preference for servers tagged
  {'a': 'value'}, but accepts any server if none matches the first
  preference.
+
+ The `server_descriptions` passed to this function should have
+ non-readable servers (e.g. RSGhost, RSArbiter, Unknown) filtered
+ out (e.g. by readable_server_selector or secondary_server_selector)
+ first.
  """
  for tag_set in tag_sets:
  selected = single_tag_set_server_selector(tag_set, server_descriptions)
@@ -81,6 +95,11 @@ def apply_local_threshold(latency_ms, server_descriptions):
  """All servers with round trip times within latency_ms of the fastest one.
 
  No ServerDescription's round_trip_time can be None.
+
+ The `server_descriptions` passed to this function should have
+ non-readable servers (e.g. RSGhost, RSArbiter, Unknown) filtered
+ out (e.g. by readable_server_selector or secondary_server_selector)
+ first.
  """
  if not server_descriptions:
  # Avoid ValueError from min() with empty sequence.
@@ -104,4 +123,5 @@ def secondary_with_tags_server_selector(tag_sets, server_descriptions):
 
 def member_with_tags_server_selector(tag_sets, server_descriptions):
  """All near-enough members matching the tag sets."""
- return tag_sets_server_selector(tag_sets, server_descriptions)
+ return tag_sets_server_selector(
+ tag_sets, readable_server_selector(server_descriptions))

test/__init__.py

@@ -127,8 +127,13 @@ def __init__(self):
  self.rs_client = pymongo.MongoClient(
  pair, replicaSet=self.replica_set_name)
 
- self.nodes = set([partition_node(node)
- for node in self.ismaster.get('hosts', [])])
+ nodes = [partition_node(node)
+ for node in self.ismaster.get('hosts', [])]
+ nodes.extend([partition_node(node)
+ for node in self.ismaster.get('passives', [])])
+ nodes.extend([partition_node(node)
+ for node in self.ismaster.get('arbiters', [])])
+ self.nodes = set(nodes)
 
  self.rs_or_standalone_client = self.rs_client or self.client
 

test/test_read_preferences.py

@@ -31,7 +31,7 @@
  Primary, PrimaryPreferred,
  Secondary, SecondaryPreferred,
  Nearest, _ServerMode)
-from pymongo.server_selectors import any_server_selector
+from pymongo.server_selectors import readable_server_selector
 from pymongo.server_type import SERVER_TYPE
 from pymongo.write_concern import WriteConcern
 
@@ -97,7 +97,7 @@ def read_from_which_kind(self, client):
  def assertReadsFrom(self, expected, **kwargs):
  c = rs_client(**kwargs)
  wait_until(
- lambda: len(c.nodes) == self.w,
+ lambda: len(c.nodes - c.arbiters) == self.w,
  "discovered all nodes")
 
  used = self.read_from_which_kind(c)
@@ -249,7 +249,8 @@ def test_nearest(self):
  latencies = ', '.join(
  '%s: %dms' % (server.description.address,
  server.description.round_trip_time)
- for server in c._get_topology().select_servers(any_server_selector))
+ for server in c._get_topology().select_servers(
+ readable_server_selector))
 
  self.assertFalse(
  not_used,