142 lines
4.9 KiB
Python
142 lines
4.9 KiB
Python
# 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.
|
|
|
|
import queue
|
|
|
|
from twisted.internet import threads
|
|
|
|
from synapse.logging.context import make_deferred_yieldable, run_in_background
|
|
|
|
|
|
class BackgroundFileConsumer:
|
|
"""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.
|
|
reactor (twisted.internet.reactor): the Twisted reactor to use
|
|
"""
|
|
|
|
# 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, reactor):
|
|
self._file_obj = file_obj
|
|
|
|
self._reactor = reactor
|
|
|
|
# Producer we're registered with
|
|
self._producer = None
|
|
|
|
# True if PushProducer, false if PullProducer
|
|
self.streaming = False
|
|
|
|
# For PushProducers, indicates whether we've paused the producer and
|
|
# need to call resumeProducing before we get more data.
|
|
self._paused_producer = 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
|
|
|
|
def registerProducer(self, producer, streaming):
|
|
"""Part of IConsumer interface
|
|
|
|
Args:
|
|
producer (IProducer)
|
|
streaming (bool): True if push based producer, False if pull
|
|
based.
|
|
"""
|
|
if self._producer:
|
|
raise Exception("registerProducer called twice")
|
|
|
|
self._producer = producer
|
|
self.streaming = streaming
|
|
self._finished_deferred = run_in_background(
|
|
threads.deferToThreadPool,
|
|
self._reactor,
|
|
self._reactor.getThreadPool(),
|
|
self._writer,
|
|
)
|
|
if not streaming:
|
|
self._producer.resumeProducing()
|
|
|
|
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 PushProducer 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:
|
|
self._reactor.callFromThread(self._resume_paused_producer)
|
|
|
|
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:
|
|
self._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()
|