Merge pull request #300 from datastax/PYTHON-160

PYTHON-160 - Token-, DC-Aware default load balancing

cassandra/cluster.py

@@ -62,7 +62,7 @@ from cassandra.protocol import (QueryMessage, ResultMessage,
                                 RESULT_KIND_SET_KEYSPACE, RESULT_KIND_ROWS,
                                 RESULT_KIND_SCHEMA_CHANGE)
 from cassandra.metadata import Metadata, protect_name
-from cassandra.policies import (RoundRobinPolicy, SimpleConvictionPolicy,
+from cassandra.policies import (TokenAwarePolicy, DCAwareRoundRobinPolicy, SimpleConvictionPolicy,
                                 ExponentialReconnectionPolicy, HostDistance,
                                 RetryPolicy)
 from cassandra.pool import (Host, _ReconnectionHandler, _HostReconnectionHandler,
@@ -169,6 +169,16 @@ def _shutdown_cluster(cluster):
         cluster.shutdown()
 
 
+# murmur3 implementation required for TokenAware is only available for CPython
+import platform
+if platform.python_implementation() == 'CPython':
+    def default_lbp_factory():
+        return TokenAwarePolicy(DCAwareRoundRobinPolicy())
+else:
+    def default_lbp_factory():
+        return DCAwareRoundRobinPolicy()
+
+
 class Cluster(object):
     """
     The main class to use when interacting with a Cassandra cluster.
@@ -193,9 +203,9 @@ class Cluster(object):
     Defaults to loopback interface.
 
     Note: When using :class:`.DCAwareLoadBalancingPolicy` with no explicit
-    local_dc set, the DC is chosen from an arbitrary host in contact_points.
-    In this case, contact_points should contain only nodes from a single,
-    local DC.
+    local_dc set (as is the default), the DC is chosen from an arbitrary
+    host in contact_points. In this case, contact_points should contain
+    only nodes from a single, local DC.
     """
 
     port = 9042
@@ -289,7 +299,16 @@ class Cluster(object):
     load_balancing_policy = None
     """
     An instance of :class:`.policies.LoadBalancingPolicy` or
-    one of its subclasses.  Defaults to :class:`~.RoundRobinPolicy`.
+    one of its subclasses.
+
+    .. versionchanged:: 2.6.0
+
+    Defaults to :class:`~.TokenAwarePolicy` (:class:`~.DCAwareRoundRobinPolicy`).
+    when using CPython (where the murmur3 extension is available). :class:`~.DCAwareRoundRobinPolicy`
+    otherwise. Default local DC will be chosen from contact points.
+
+    **Please see** :class:`~.DCAwareRoundRobinPolicy` **for a discussion on default behavior with respect to
+    DC locality and remote nodes.**
     """
 
     reconnection_policy = ExponentialReconnectionPolicy(1.0, 600.0)
@@ -319,6 +338,8 @@ class Cluster(object):
     by the :attr:`~.Cluster.load_balancing_policy` will have a connection
     opened to them.  Otherwise, they will not have a connection opened to them.
 
+    Note that the default load balancing policy ignores remote hosts by default.
+
     .. versionadded:: 2.1.0
     """
 
@@ -503,7 +524,7 @@ class Cluster(object):
 
             self.load_balancing_policy = load_balancing_policy
         else:
-            self.load_balancing_policy = RoundRobinPolicy()
+            self.load_balancing_policy = default_lbp_factory()
 
         if reconnection_policy is not None:
             if isinstance(reconnection_policy, type):
@@ -2114,20 +2135,21 @@ class ControlConnection(object):
         return None
 
     def shutdown(self):
+        # stop trying to reconnect (if we are)
+        with self._reconnection_lock:
+            if self._reconnection_handler:
+                self._reconnection_handler.cancel()
+
         with self._lock:
             if self._is_shutdown:
                 return
             else:
                 self._is_shutdown = True
 
-        log.debug("Shutting down control connection")
-        # stop trying to reconnect (if we are)
-        if self._reconnection_handler:
-            self._reconnection_handler.cancel()
-
-        if self._connection:
-            self._connection.close()
-            del self._connection
+            log.debug("Shutting down control connection")
+            if self._connection:
+                self._connection.close()
+                del self._connection
 
     def refresh_schema(self, keyspace=None, table=None, usertype=None, function=None,
                        aggregate=None, schema_agreement_wait=None):
@@ -2545,17 +2567,21 @@ class ControlConnection(object):
         return dict((version, list(nodes)) for version, nodes in six.iteritems(versions))
 
     def _signal_error(self):
-        # try just signaling the cluster, as this will trigger a reconnect
-        # as part of marking the host down
-        if self._connection and self._connection.is_defunct:
-            host = self._cluster.metadata.get_host(self._connection.host)
-            # host may be None if it's already been removed, but that indicates
-            # that errors have already been reported, so we're fine
-            if host:
-                self._cluster.signal_connection_failure(
-                    host, self._connection.last_error, is_host_addition=False)
+        with self._lock:
+            if self._is_shutdown:
                 return
 
+            # try just signaling the cluster, as this will trigger a reconnect
+            # as part of marking the host down
+            if self._connection and self._connection.is_defunct:
+                host = self._cluster.metadata.get_host(self._connection.host)
+                # host may be None if it's already been removed, but that indicates
+                # that errors have already been reported, so we're fine
+                if host:
+                    self._cluster.signal_connection_failure(
+                        host, self._connection.last_error, is_host_addition=False)
+                    return
+
         # if the connection is not defunct or the host already left, reconnect
         # manually
         self.reconnect()

tests/integration/__init__.py

@@ -232,7 +232,7 @@ def teardown_package():
                 log.exception('Failed to remove cluster: %s' % cluster_name)
 
         except Exception:
-            log.warn('Did not find cluster: %s' % cluster_name)
+            log.warning('Did not find cluster: %s' % cluster_name)
 
 
 def setup_keyspace(ipformat=None):