Fix tracing with non-default row_factory

For PYTHON-49

CHANGELOG.rst

@@ -13,6 +13,8 @@ Bug Fixes
   Cassandra is a multiple of the read buffer size.  Previously, if no more data
   became available to read on the socket, the message would never be processed,
   resulting in an OperationTimedOut error.
+* Don't break tracing when a Session's row_factory is not the default
+  namedtuple_factory.
 
 Other
 -----

cassandra/cluster.py

@@ -1039,6 +1039,12 @@ class Session(object):
             ...     log.exception("Operation failed:")
 
         """
+        future = self._create_response_future(query, parameters, trace)
+        future.send_request()
+        return future
+
+    def _create_response_future(self, query, parameters, trace):
+        """ Returns the ResponseFuture before calling send_request() on it """
         prepared_statement = None
         if isinstance(query, basestring):
             query = SimpleStatement(query)
@@ -1060,11 +1066,9 @@ class Session(object):
         if trace:
             message.tracing = True
 
-        future = ResponseFuture(
+        return ResponseFuture(
             self, message, query, self.default_timeout, metrics=self._metrics,
             prepared_statement=prepared_statement)
-        future.send_request()
-        return future
 
     def prepare(self, query):
         """

cassandra/query.py

@@ -8,10 +8,10 @@ from datetime import datetime, timedelta
 import struct
 import time
 
-from cassandra import ConsistencyLevel
+from cassandra import ConsistencyLevel, OperationTimedOut
 from cassandra.cqltypes import unix_time_from_uuid1
 from cassandra.decoder import (cql_encoders, cql_encode_object,
-                               cql_encode_sequence)
+                               cql_encode_sequence, named_tuple_factory)
 
 import logging
 log = logging.getLogger(__name__)
@@ -409,9 +409,13 @@ class QueryTrace(object):
         attempt = 0
         start = time.time()
         while True:
-            if max_wait is not None and time.time() - start >= max_wait:
+            time_spent = time.time() - start
+            if max_wait is not None and time_spent >= max_wait:
                 raise TraceUnavailable("Trace information was not available within %f seconds" % (max_wait,))
-            session_results = self._session.execute(self._SELECT_SESSIONS_FORMAT, (self.trace_id,))
+
+            session_results = self._execute(
+                self._SELECT_SESSIONS_FORMAT, (self.trace_id,), time_spent, max_wait)
+
             if not session_results or session_results[0].duration is None:
                 time.sleep(self._BASE_RETRY_SLEEP * (2 ** attempt))
                 attempt += 1
@@ -424,11 +428,25 @@ class QueryTrace(object):
             self.coordinator = session_row.coordinator
             self.parameters = session_row.parameters
 
-            event_results = self._session.execute(self._SELECT_EVENTS_FORMAT, (self.trace_id,))
+            time_spent = time.time() - start
+            event_results = self._execute(
+                self._SELECT_EVENTS_FORMAT, (self.trace_id,), time_spent, max_wait)
             self.events = tuple(TraceEvent(r.activity, r.event_id, r.source, r.source_elapsed, r.thread)
                                 for r in event_results)
             break
 
+    def _execute(self, query, parameters, time_spent, max_wait):
+        # in case the user switched the row factory, set it to namedtuple for this query
+        future = self._session._create_response_future(query, parameters, trace=False)
+        future.row_factory = named_tuple_factory
+        future.send_request()
+
+        timeout = (max_wait - time_spent) if max_wait is not None else None
+        try:
+            return future.result(timeout=timeout)
+        except OperationTimedOut:
+            raise TraceUnavailable("Trace information was not available within %f seconds" % (max_wait,))
+
     def __str__(self):
         return "%s [%s] coordinator: %s, started at: %s, duration: %s, parameters: %s" \
                % (self.request_type, self.trace_id, self.coordinator, self.started_at,

tests/integration/standard/test_query.py

@@ -5,6 +5,7 @@ except ImportError:
 
 from cassandra.query import PreparedStatement, BoundStatement, ValueSequence, SimpleStatement
 from cassandra.cluster import Cluster
+from cassandra.decoder import dict_factory
 
 
 class QueryTest(unittest.TestCase):
@@ -49,6 +50,20 @@ class QueryTest(unittest.TestCase):
         for event in statement.trace.events:
             str(event)
 
+    def test_trace_ignores_row_factory(self):
+        cluster = Cluster()
+        session = cluster.connect()
+        session.row_factory = dict_factory
+
+        query = "SELECT * FROM system.local"
+        statement = SimpleStatement(query)
+        session.execute(statement, trace=True)
+
+        # Ensure this does not throw an exception
+        str(statement.trace)
+        for event in statement.trace.events:
+            str(event)
+
 
 class PreparedStatementTests(unittest.TestCase):