Add decent impl of a FileConsumer
Twisted core doesn't have a general purpose one, so we need to write one ourselves. Features: - All writing happens in background thread - Supports both push and pull producers - Push producers get paused if the consumer falls behindpull/2804/head
Erik Johnston
parent
3cb2dabaad
commit
bc67e7d260
|
|
@ -0,0 +1,158 @@
|
|||
# -*- coding: utf-8 -*-
|
||||
# Copyright 2018 New Vecotr Ltd
|
||||
#
|
||||
# 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.
|
||||
|
||||
from twisted.internet import defer, threads, reactor
|
||||
|
||||
from synapse.util.logcontext import make_deferred_yieldable
|
||||
|
||||
import Queue
|
||||
|
||||
|
||||
class BackgroundFileConsumer(object):
|
||||
"""A consumer that writes to a file like object. Supports both push
|
||||
and pull producers
|
||||
|
||||
Args:
|
||||
file_obj (file): The file like object to write to. Closed when
|
||||
finished.
|
||||
"""
|
||||
|
||||
# For PushProducers pause if we have this many unwritten slices
|
||||
_PAUSE_ON_QUEUE_SIZE = 5
|
||||
# And resume once the size of the queue is less than this
|
||||
_RESUME_ON_QUEUE_SIZE = 2
|
||||
|
||||
def __init__(self, file_obj):
|
||||
self.file_obj = file_obj
|
||||
|
||||
# Producer we're registered with
|
||||
self.producer = None
|
||||
|
||||
# True if PushProducer, false if PullProducer
|
||||
self.streaming = False
|
||||
|
||||
# Queue of slices of bytes to be written. When producer calls
|
||||
# unregister a final None is sent.
|
||||
self.bytes_queue = Queue.Queue()
|
||||
|
||||
# Deferred that is resolved when finished writing
|
||||
self.finished_deferred = None
|
||||
|
||||
# If the _writer thread throws an exception it gets stored here.
|
||||
self._write_exception = None
|
||||
|
||||
# A deferred that gets resolved when the bytes_queue gets empty.
|
||||
# Mainly used for tests.
|
||||
self._notify_empty_deferred = None
|
||||
|
||||
def registerProducer(self, producer, streaming):
|
||||
"""Part of IProducer interface
|
||||
|
||||
Args:
|
||||
producer (IProducer)
|
||||
streaming (bool): True if push based producer, False if pull
|
||||
based.
|
||||
"""
|
||||
self.producer = producer
|
||||
self.streaming = streaming
|
||||
self.finished_deferred = threads.deferToThread(self._writer)
|
||||
if not streaming:
|
||||
self.producer.resumeProducing()
|
||||
|
||||
self.paused_producer = False
|
||||
|
||||
def unregisterProducer(self):
|
||||
"""Part of IProducer interface
|
||||
"""
|
||||
self.producer = None
|
||||
if not self.finished_deferred.called:
|
||||
self.bytes_queue.put_nowait(None)
|
||||
|
||||
def write(self, bytes):
|
||||
"""Part of IProducer interface
|
||||
"""
|
||||
if self._write_exception:
|
||||
raise self._write_exception
|
||||
|
||||
if self.finished_deferred.called:
|
||||
raise Exception("consumer has closed")
|
||||
|
||||
self.bytes_queue.put_nowait(bytes)
|
||||
|
||||
# If this is a pushed based consumer and the queue is getting behind
|
||||
# then we pause the producer.
|
||||
if self.streaming and self.bytes_queue.qsize() >= self._PAUSE_ON_QUEUE_SIZE:
|
||||
self.paused_producer = True
|
||||
self.producer.pauseProducing()
|
||||
|
||||
def _writer(self):
|
||||
"""This is run in a background thread to write to the file.
|
||||
"""
|
||||
try:
|
||||
while self.producer or not self.bytes_queue.empty():
|
||||
# If we've paused the producer check if we should resume the
|
||||
# producer.
|
||||
if self.producer and self.paused_producer:
|
||||
if self.bytes_queue.qsize() <= self._RESUME_ON_QUEUE_SIZE:
|
||||
reactor.callFromThread(self._resume_paused_producer)
|
||||
|
||||
if self._notify_empty and self.bytes_queue.empty():
|
||||
reactor.callFromThread(self._notify_empty)
|
||||
|
||||
bytes = self.bytes_queue.get()
|
||||
|
||||
# If we get a None (or empty list) then that's a signal used
|
||||
# to indicate we should check if we should stop.
|
||||
if bytes:
|
||||
self.file_obj.write(bytes)
|
||||
|
||||
# If its a pull producer then we need to explicitly ask for
|
||||
# more stuff.
|
||||
if not self.streaming and self.producer:
|
||||
reactor.callFromThread(self.producer.resumeProducing)
|
||||
except Exception as e:
|
||||
self._write_exception = e
|
||||
raise
|
||||
finally:
|
||||
self.file_obj.close()
|
||||
|
||||
def wait(self):
|
||||
"""Returns a deferred that resolves when finished writing to file
|
||||
"""
|
||||
return make_deferred_yieldable(self.finished_deferred)
|
||||
|
||||
def _resume_paused_producer(self):
|
||||
"""Gets called if we should resume producing after being paused
|
||||
"""
|
||||
if self.paused_producer and self.producer:
|
||||
self.paused_producer = False
|
||||
self.producer.resumeProducing()
|
||||
|
||||
def _notify_empty(self):
|
||||
"""Called when the _writer thread thinks the queue may be empty and
|
||||
we should notify anything waiting on `wait_for_writes`
|
||||
"""
|
||||
if self._notify_empty_deferred and self.bytes_queue.empty():
|
||||
d = self._notify_empty_deferred
|
||||
self._notify_empty_deferred = None
|
||||
d.callback(None)
|
||||
|
||||
def wait_for_writes(self):
|
||||
"""Wait for the write queue to be empty and for writes to have
|
||||
finished. This is mainly useful for tests.
|
||||
"""
|
||||
if not self._notify_empty_deferred:
|
||||
self._notify_empty_deferred = defer.Deferred()
|
||||
return self._notify_empty_deferred
|
||||
|
|
@ -0,0 +1,138 @@
|
|||
# -*- coding: utf-8 -*-
|
||||
# Copyright 2018 New Vector Ltd
|
||||
#
|
||||
# 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.
|
||||
|
||||
|
||||
from twisted.internet import defer
|
||||
from mock import NonCallableMock
|
||||
|
||||
from synapse.util.file_consumer import BackgroundFileConsumer
|
||||
|
||||
from tests import unittest
|
||||
from StringIO import StringIO
|
||||
|
||||
import threading
|
||||
|
||||
|
||||
class FileConsumerTests(unittest.TestCase):
|
||||
|
||||
@defer.inlineCallbacks
|
||||
def test_pull_consumer(self):
|
||||
string_file = StringIO()
|
||||
consumer = BackgroundFileConsumer(string_file)
|
||||
|
||||
try:
|
||||
producer = DummyPullProducer()
|
||||
|
||||
yield producer.register_with_consumer(consumer)
|
||||
|
||||
yield producer.write_and_wait("Foo")
|
||||
|
||||
self.assertEqual(string_file.getvalue(), "Foo")
|
||||
|
||||
yield producer.write_and_wait("Bar")
|
||||
|
||||
self.assertEqual(string_file.getvalue(), "FooBar")
|
||||
finally:
|
||||
consumer.unregisterProducer()
|
||||
|
||||
yield consumer.wait()
|
||||
|
||||
self.assertTrue(string_file.closed)
|
||||
|
||||
@defer.inlineCallbacks
|
||||
def test_push_consumer(self):
|
||||
string_file = StringIO()
|
||||
consumer = BackgroundFileConsumer(string_file)
|
||||
|
||||
try:
|
||||
producer = NonCallableMock(spec_set=[])
|
||||
|
||||
consumer.registerProducer(producer, True)
|
||||
|
||||
consumer.write("Foo")
|
||||
yield consumer.wait_for_writes()
|
||||
|
||||
self.assertEqual(string_file.getvalue(), "Foo")
|
||||
|
||||
consumer.write("Bar")
|
||||
yield consumer.wait_for_writes()
|
||||
|
||||
self.assertEqual(string_file.getvalue(), "FooBar")
|
||||
finally:
|
||||
consumer.unregisterProducer()
|
||||
|
||||
yield consumer.wait()
|
||||
|
||||
self.assertTrue(string_file.closed)
|
||||
|
||||
@defer.inlineCallbacks
|
||||
def test_push_producer_feedback(self):
|
||||
string_file = BlockingStringWrite()
|
||||
consumer = BackgroundFileConsumer(string_file)
|
||||
|
||||
try:
|
||||
producer = NonCallableMock(spec_set=["pauseProducing", "resumeProducing"])
|
||||
|
||||
consumer.registerProducer(producer, True)
|
||||
|
||||
with string_file.write_lock:
|
||||
for _ in range(consumer._PAUSE_ON_QUEUE_SIZE):
|
||||
consumer.write("Foo")
|
||||
|
||||
producer.pauseProducing.assert_called_once()
|
||||
|
||||
yield consumer.wait_for_writes()
|
||||
producer.resumeProducing.assert_called_once()
|
||||
finally:
|
||||
consumer.unregisterProducer()
|
||||
|
||||
yield consumer.wait()
|
||||
|
||||
self.assertTrue(string_file.closed)
|
||||
|
||||
|
||||
class DummyPullProducer(object):
|
||||
def __init__(self):
|
||||
self.consumer = None
|
||||
self.deferred = defer.Deferred()
|
||||
|
||||
def resumeProducing(self):
|
||||
d = self.deferred
|
||||
self.deferred = defer.Deferred()
|
||||
d.callback(None)
|
||||
|
||||
def write_and_wait(self, bytes):
|
||||
d = self.deferred
|
||||
self.consumer.write(bytes)
|
||||
return d
|
||||
|
||||
def register_with_consumer(self, consumer):
|
||||
d = self.deferred
|
||||
self.consumer = consumer
|
||||
self.consumer.registerProducer(self, False)
|
||||
return d
|
||||
|
||||
|
||||
class BlockingStringWrite(object):
|
||||
def __init__(self):
|
||||
self.buffer = ""
|
||||
self.closed = False
|
||||
self.write_lock = threading.Lock()
|
||||
|
||||
def write(self, bytes):
|
||||
self.buffer += bytes
|
||||
|
||||
def close(self):
|
||||
self.closed = True
|
||||
Loading…
Reference in New Issue