Add decent impl of a FileConsumer #2804
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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 behind
synapse/util/file_consumer.py
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| # -*- coding: utf-8 -*- | |||
| # Copyright 2018 New Vecotr Ltd | |||
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it's almost as if you're typing this by hand instead of having your editor generate it...
synapse/util/file_consumer.py
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| self._notify_empty_deferred = None | ||
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| def registerProducer(self, producer, streaming): | ||
| """Part of IProducer interface |
synapse/util/file_consumer.py
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| if not streaming: | ||
| self.producer.resumeProducing() | ||
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| self.paused_producer = False |
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can we declare this in the constructor?
synapse/util/file_consumer.py
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| _RESUME_ON_QUEUE_SIZE = 2 | ||
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| def __init__(self, file_obj): | ||
| self.file_obj = file_obj |
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is there a reason that some fields get underscores and some do not? I'd say they all should have one
synapse/util/file_consumer.py
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| self.bytes_queue.put_nowait(bytes) | ||
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| # If this is a pushed based consumer and the queue is getting behind |
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s/pushed based consumer/PushProducer/ ?
synapse/util/file_consumer.py
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| streaming (bool): True if push based producer, False if pull | ||
| based. | ||
| """ | ||
| self.producer = producer |
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should we have some sanity checks to prevent registering twice?
synapse/util/file_consumer.py
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| if self.bytes_queue.qsize() <= self._RESUME_ON_QUEUE_SIZE: | ||
| reactor.callFromThread(self._resume_paused_producer) | ||
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| if self._notify_empty and self.bytes_queue.empty(): |
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self._notify_empty is always truthy
synapse/util/file_consumer.py
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| # producer. | ||
| if self.producer and self.paused_producer: | ||
| if self.bytes_queue.qsize() <= self._RESUME_ON_QUEUE_SIZE: | ||
| reactor.callFromThread(self._resume_paused_producer) |
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does this block until the callee finishes, or not? if not we could end up resuming multiple times - is that a problem?
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I'm fairly sure it doesn't, and its not a problem as _resume_paused_producer checks self.paused_producer again anyway.
synapse/util/file_consumer.py
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| def wait(self): | ||
| """Returns a deferred that resolves when finished writing to file | ||
| """ | ||
| return make_deferred_yieldable(self.finished_deferred) |
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why does this make_deferred_yieldable when nothing else does?
tests/util/test_file_consumer.py
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| consumer.registerProducer(producer, True) | ||
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| consumer.write("Foo") | ||
| yield consumer.wait_for_writes() |
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I kinda feel like this might be better done by having the test file object let you wait for writes, rather than having the extra functionality in the consumer solely for testing, but ymmv
erikjohnston
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Twisted core doesn't have a general purpose one, so we need to write one
ourselves.
Features: