openstack/deb-python-cassandra-driver
Code Issues Proposed changes

More complete token-aware routing

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The TokenAwarePolicy now takes into account what keyspace the
query is being run against so that replication settings can
be taken into account.  This means that all replicas for
the queried row can be used instead of just the first replica.
This commit is contained in:
Tyler Hobbs
2013-09-18 17:02:43 -05:00
parent f3d75e75cf
commit 54699cbc04
6 changed files with 105 additions and 49 deletions
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25
cassandra/policies.py
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@@ -71,7 +71,7 @@ class LoadBalancingPolicy(object):
"""
raise NotImplementedError()
def make_query_plan(self, query=None):
def make_query_plan(self, working_keyspace=None, query=None):
"""
Given a :class:`~.query.Query` instance, return a iterable
of :class:`.Host` instances which should be queried in that
@@ -80,6 +80,10 @@ class LoadBalancingPolicy(object):
Note that the `query` argument may be :const:`None` when preparing
statements.
`working_keyspace` should be the string name of the current keyspace,
as set through :meth:`.Session.set_keyspace()` or with a ``USE``
statement.
"""
raise NotImplementedError()
@@ -133,7 +137,7 @@ class RoundRobinPolicy(LoadBalancingPolicy):
def distance(self, host):
return HostDistance.LOCAL
def make_query_plan(self, query=None):
def make_query_plan(self, working_keyspace=None, query=None):
# not thread-safe, but we don't care much about lost increments
# for the purposes of load balancing
pos = self._position
@@ -219,7 +223,7 @@ class DCAwareRoundRobinPolicy(LoadBalancingPolicy):
else:
return HostDistance.IGNORED
def make_query_plan(self, query=None):
def make_query_plan(self, working_keyspace=None, query=None):
# not thread-safe, but we don't care much about lost increments
# for the purposes of load balancing
pos = self._position
@@ -278,24 +282,29 @@ class TokenAwarePolicy(LoadBalancingPolicy):
def distance(self, *args, **kwargs):
return self.child_policy.distance(*args, **kwargs)
def make_query_plan(self, query=None):
def make_query_plan(self, working_keyspace=None, query=None):
if query and query.keyspace:
keyspace = query.keyspace
else:
keyspace = working_keyspace
child = self.child_policy
if query is None:
for host in child.make_query_plan(query):
for host in child.make_query_plan(keyspace, query):
yield host
else:
routing_key = query.routing_key
if routing_key is None:
for host in child.make_query_plan(query):
for host in child.make_query_plan(keyspace, query):
yield host
else:
replicas = self._cluster_metadata.get_replicas(routing_key)
replicas = self._cluster_metadata.get_replicas(keyspace, routing_key)
for replica in replicas:
if replica.monitor.is_up and \
child.distance(replica) == HostDistance.LOCAL:
yield replica
for host in child.make_query_plan(query):
for host in child.make_query_plan(keyspace, query):
# skip if we've already listed this host
if host not in replicas or \
child.distance(host) == HostDistance.REMOTE: