197 lines
7.1 KiB
Python
197 lines
7.1 KiB
Python
# Copyright 2013-2014 DataStax, Inc.
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License");
|
|
# you may not use this file except in compliance with the License.
|
|
# You may obtain a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS,
|
|
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
# See the License for the specific language governing permissions and
|
|
# limitations under the License.
|
|
|
|
import six
|
|
import sys
|
|
|
|
from itertools import count, cycle
|
|
import logging
|
|
from six.moves import xrange
|
|
from threading import Event
|
|
|
|
from cassandra.cluster import PagedResult
|
|
|
|
log = logging.getLogger(__name__)
|
|
|
|
|
|
def execute_concurrent(session, statements_and_parameters, concurrency=100, raise_on_first_error=True):
|
|
"""
|
|
Executes a sequence of (statement, parameters) tuples concurrently. Each
|
|
``parameters`` item must be a sequence or :const:`None`.
|
|
|
|
A sequence of ``(success, result_or_exc)`` tuples 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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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
|
|
|
|
"""
|
|
if concurrency <= 0:
|
|
raise ValueError("concurrency must be greater than 0")
|
|
|
|
if not statements_and_parameters:
|
|
return []
|
|
|
|
# TODO handle iterators and generators naturally without converting the
|
|
# whole thing to a list. This would require not building a result
|
|
# list of Nones up front (we don't know how many results there will be),
|
|
# so a dict keyed by index should be used instead. The tricky part is
|
|
# knowing when you're the final statement to finish.
|
|
statements_and_parameters = list(statements_and_parameters)
|
|
|
|
event = Event()
|
|
first_error = [] if raise_on_first_error else None
|
|
to_execute = len(statements_and_parameters)
|
|
results = [None] * to_execute
|
|
num_finished = count(1)
|
|
statements = enumerate(iter(statements_and_parameters))
|
|
for i in xrange(min(concurrency, len(statements_and_parameters))):
|
|
_execute_next(_sentinel, i, event, session, statements, results, None, num_finished, to_execute, first_error)
|
|
|
|
event.wait()
|
|
if first_error:
|
|
exc = first_error[0]
|
|
if six.PY2 and isinstance(exc, tuple):
|
|
(exc_type, value, traceback) = exc
|
|
six.reraise(exc_type, value, traceback)
|
|
else:
|
|
raise exc
|
|
else:
|
|
return results
|
|
|
|
|
|
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)
|
|
"""
|
|
return execute_concurrent(session, list(zip(cycle((statement,)), parameters)), *args, **kwargs)
|
|
|
|
|
|
_sentinel = object()
|
|
|
|
|
|
def _handle_error(error, result_index, event, session, statements, results,
|
|
future, num_finished, to_execute, first_error):
|
|
if first_error is not None:
|
|
first_error.append(error)
|
|
event.set()
|
|
return
|
|
else:
|
|
results[result_index] = (False, error)
|
|
if next(num_finished) >= to_execute:
|
|
event.set()
|
|
return
|
|
|
|
try:
|
|
(next_index, (statement, params)) = next(statements)
|
|
except StopIteration:
|
|
return
|
|
|
|
try:
|
|
future = session.execute_async(statement, params)
|
|
args = (next_index, event, session, statements, results, future, num_finished, to_execute, first_error)
|
|
future.add_callbacks(
|
|
callback=_execute_next, callback_args=args,
|
|
errback=_handle_error, errback_args=args)
|
|
except Exception as exc:
|
|
if first_error is not None:
|
|
if six.PY2:
|
|
first_error.append(sys.exc_info())
|
|
else:
|
|
first_error.append(exc)
|
|
event.set()
|
|
return
|
|
else:
|
|
results[next_index] = (False, exc)
|
|
if next(num_finished) >= to_execute:
|
|
event.set()
|
|
return
|
|
|
|
|
|
def _execute_next(result, result_index, event, session, statements, results,
|
|
future, num_finished, to_execute, first_error):
|
|
if result is not _sentinel:
|
|
if future.has_more_pages:
|
|
result = PagedResult(future, result)
|
|
future.clear_callbacks()
|
|
results[result_index] = (True, result)
|
|
finished = next(num_finished)
|
|
if finished >= to_execute:
|
|
event.set()
|
|
return
|
|
|
|
try:
|
|
(next_index, (statement, params)) = next(statements)
|
|
except StopIteration:
|
|
return
|
|
|
|
try:
|
|
future = session.execute_async(statement, params)
|
|
args = (next_index, event, session, statements, results, future, num_finished, to_execute, first_error)
|
|
future.add_callbacks(
|
|
callback=_execute_next, callback_args=args,
|
|
errback=_handle_error, errback_args=args)
|
|
except Exception as exc:
|
|
if first_error is not None:
|
|
if six.PY2:
|
|
first_error.append(sys.exc_info())
|
|
else:
|
|
first_error.append(exc)
|
|
event.set()
|
|
return
|
|
else:
|
|
results[next_index] = (False, exc)
|
|
if next(num_finished) >= to_execute:
|
|
event.set()
|
|
return
|