add Session.execute_concurrent and execute_concurrent_with_args

Author: Jonathan Ellis

cassandra/cluster.py

@@ -81,6 +81,7 @@
 from cassandra.marshal import int64_pack
 from cassandra.timestamps import MonotonicTimestampGenerator
 from cassandra.util import _resolve_contact_points_to_string_map, Version
+from cassandra.concurrent import execute_concurrent, execute_concurrent_with_args
 
 from cassandra.datastax.insights.reporter import MonitorReporter
 from cassandra.datastax.insights.util import version_supports_insights
@@ -2725,6 +2726,79 @@ def execute_async(self, query, parameters=None, trace=False, custom_payload=None
         future.send_request()
         return future
 
+    def execute_concurrent(self, statements_and_parameters, concurrency=100, raise_on_first_error=True, results_generator=False, execution_profile=EXEC_PROFILE_DEFAULT):
+        """
+        Executes a sequence of (statement, parameters) tuples concurrently.  Each
+        ``parameters`` item must be a sequence or :const:`None`.
+
+        The `concurrency` parameter controls how many statements will be executed
+        concurrently.  When :attr:`.Cluster.protocol_version` is set to 1 or 2,
+        it is recommended that this be kept below 100 times the number of
+        core connections per host times the number of connected hosts (see
+        :meth:`.Cluster.set_core_connections_per_host`).  If that amount is exceeded,
+        the event loop thread may attempt to block on new connection creation,
+        substantially impacting throughput.  If :attr:`~.Cluster.protocol_version`
+        is 3 or higher, you can safely experiment with higher levels of concurrency.
+
+        If `raise_on_first_error` is left as :const:`True`, execution will stop
+        after the first failed statement and the corresponding exception will be
+        raised.
+
+        `results_generator` controls how the results are returned.
+
+        * If :const:`False`, the results are returned only after all requests have completed.
+        * If :const:`True`, a generator expression is returned. Using a generator results in a constrained
+          memory footprint when the results set will be large -- results are yielded
+          as they return instead of materializing the entire list at once. The trade for lower memory
+          footprint is marginal CPU overhead (more thread coordination and sorting out-of-order results
+          on-the-fly).
+
+        `execution_profile` argument is the execution profile to use for this
+        request, it is passed directly to :meth:`Session.execute_async`.
+
+        A sequence of ``ExecutionResult(success, result_or_exc)`` namedtuples is returned
+        in the same order that the statements were passed in.  If ``success`` is :const:`False`,
+        there was an error executing the statement, and ``result_or_exc``
+        will be an :class:`Exception`.  If ``success`` is :const:`True`, ``result_or_exc``
+        will be the query result.
+
+        Example usage::
+
+            select_statement = session.prepare("SELECT * FROM users WHERE id=?")
+
+            statements_and_params = []
+            for user_id in user_ids:
+                params = (user_id, )
+                statements_and_params.append((select_statement, params))
+
+            results = session.execute_concurrent(statements_and_params, raise_on_first_error=False)
+
+            for (success, result) in results:
+                if not success:
+                    handle_error(result)  # result will be an Exception
+                else:
+                    process_user(result[0])  # result will be a list of rows
+
+        Note: in the case that `generators` are used, it is important to ensure the consumers do not
+        block or attempt further synchronous requests, because no further IO will be processed until
+        the consumer returns. This may also produce a deadlock in the IO event thread.
+        """
+        return execute_concurrent(self, statements_and_parameters, concurrency, raise_on_first_error, results_generator, execution_profile)
+
+    def execute_concurrent_with_args(self, statement, parameters, *args, **kwargs):
+        """
+        Like :meth:`~cassandra.concurrent.execute_concurrent()`, but takes a single
+        statement and a sequence of parameters.  Each item in ``parameters``
+        should be a sequence or :const:`None`.
+
+        Example usage::
+
+            statement = session.prepare("INSERT INTO mytable (a, b) VALUES (1, ?)")
+            parameters = [(x,) for x in range(1000)]
+            session.execute_concurrent_with_args(statement, parameters, concurrency=50)
+        """
+        return execute_concurrent_with_args(self, statement, parameters, *args, **kwargs)
+
     def execute_graph(self, query, parameters=None, trace=False, execution_profile=EXEC_PROFILE_GRAPH_DEFAULT, execute_as=None):
         """
         Executes a Gremlin query string or GraphStatement synchronously,

cassandra/concurrent.py

@@ -29,61 +29,7 @@
 
 def execute_concurrent(session, statements_and_parameters, concurrency=100, raise_on_first_error=True, results_generator=False, execution_profile=EXEC_PROFILE_DEFAULT):
     """
-    Executes a sequence of (statement, parameters) tuples concurrently.  Each
-    ``parameters`` item must be a sequence or :const:`None`.
-
-    The `concurrency` parameter controls how many statements will be executed
-    concurrently.  When :attr:`.Cluster.protocol_version` is set to 1 or 2,
-    it is recommended that this be kept below 100 times the number of
-    core connections per host times the number of connected hosts (see
-    :meth:`.Cluster.set_core_connections_per_host`).  If that amount is exceeded,
-    the event loop thread may attempt to block on new connection creation,
-    substantially impacting throughput.  If :attr:`~.Cluster.protocol_version`
-    is 3 or higher, you can safely experiment with higher levels of concurrency.
-
-    If `raise_on_first_error` is left as :const:`True`, execution will stop
-    after the first failed statement and the corresponding exception will be
-    raised.
-
-    `results_generator` controls how the results are returned.
-
-    * If :const:`False`, the results are returned only after all requests have completed.
-    * If :const:`True`, a generator expression is returned. Using a generator results in a constrained
-      memory footprint when the results set will be large -- results are yielded
-      as they return instead of materializing the entire list at once. The trade for lower memory
-      footprint is marginal CPU overhead (more thread coordination and sorting out-of-order results
-      on-the-fly).
-
-    `execution_profile` argument is the execution profile to use for this
-    request, it is passed directly to :meth:`Session.execute_async`.
-
-    A sequence of ``ExecutionResult(success, result_or_exc)`` namedtuples is returned
-    in the same order that the statements were passed in.  If ``success`` is :const:`False`,
-    there was an error executing the statement, and ``result_or_exc`` will be
-    an :class:`Exception`.  If ``success`` is :const:`True`, ``result_or_exc``
-    will be the query result.
-
-    Example usage::
-
-        select_statement = session.prepare("SELECT * FROM users WHERE id=?")
-
-        statements_and_params = []
-        for user_id in user_ids:
-            params = (user_id, )
-            statements_and_params.append((select_statement, params))
-
-        results = execute_concurrent(
-            session, statements_and_params, raise_on_first_error=False)
-
-        for (success, result) in results:
-            if not success:
-                handle_error(result)  # result will be an Exception
-            else:
-                process_user(result[0])  # result will be a list of rows
-
-    Note: in the case that `generators` are used, it is important to ensure the consumers do not
-    block or attempt further synchronous requests, because no further IO will be processed until
-    the consumer returns. This may also produce a deadlock in the IO event thread.
+    See :meth:`.Session.execute_concurrent`.
     """
     if concurrency <= 0:
         raise ValueError("concurrency must be greater than 0")
@@ -216,14 +162,6 @@ def _results(self):
 
 def execute_concurrent_with_args(session, statement, parameters, *args, **kwargs):
     """
-    Like :meth:`~cassandra.concurrent.execute_concurrent()`, but takes a single
-    statement and a sequence of parameters.  Each item in ``parameters``
-    should be a sequence or :const:`None`.
-
-    Example usage::
-
-        statement = session.prepare("INSERT INTO mytable (a, b) VALUES (1, ?)")
-        parameters = [(x,) for x in range(1000)]
-        execute_concurrent_with_args(session, statement, parameters, concurrency=50)
+    See :meth:`.Session.execute_concurrent_with_args`.
     """
     return execute_concurrent(session, zip(cycle((statement,)), parameters), *args, **kwargs)