Use a `trio.Event` to guarantee respawning of data feed task
Tyler Goodlet
parent
01c0551a7f
commit
66ecb4c0cb
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@ -108,6 +108,9 @@ async def stream_quotes(
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await trio.sleep(delay)
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# TODO: at this point probably just just make this a class and
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# a lot of these functions should be methods. It will definitely
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# make stateful UI apps easier to implement
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class DataFeed(typing.NamedTuple):
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"""A per broker "data feed" container.
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@ -118,7 +121,7 @@ class DataFeed(typing.NamedTuple):
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client: object
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exit_stack: contextlib.AsyncExitStack
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quoter_keys: List[str] = ['stock', 'option']
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tasks: Dict[str, trio._core._run.Task] = dict.fromkeys(
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tasks: Dict[str, trio.Event] = dict.fromkeys(
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quoter_keys, False)
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quoters: Dict[str, typing.Coroutine] = {}
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subscriptions: Dict[str, Dict[str, set]] = {'option': {}, 'stock': {}}
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@ -234,13 +237,19 @@ async def smoke_quote(get_quotes, tickers, broker):
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###########################################
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async def modify_quote_stream(broker, feed_type, symbols, chan=None, cid=None):
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def modify_quote_stream(broker, feed_type, symbols, chan, cid):
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"""Absolute symbol subscription list for each quote stream.
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Effectively a symbol subscription api.
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"""
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log.info(f"{chan} changed symbol subscription to {symbols}")
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feed = await get_cached_feed(broker)
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ss = tractor.current_actor().statespace
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feed = ss['feeds'].get(broker)
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if feed is None:
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raise RuntimeError(
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"`get_cached_feed()` must be called before modifying its stream"
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)
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symbols2chans = feed.subscriptions[feed_type]
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# update map from each symbol to requesting client's chan
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for ticker in symbols:
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@ -299,6 +308,7 @@ async def start_quote_stream(
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diff_cached: bool = True,
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chan: tractor.Channel = None,
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cid: str = None,
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rate: int = 3,
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) -> None:
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"""Handle per-broker quote stream subscriptions using a "lazy" pub-sub
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pattern.
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@ -311,7 +321,6 @@ async def start_quote_stream(
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# set log level after fork
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get_console_log(actor.loglevel)
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# pull global vars from local actor
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ss = actor.statespace
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symbols = list(symbols)
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log.info(
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f"{chan.uid} subscribed to {broker} for symbols {symbols}")
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@ -337,17 +346,36 @@ async def start_quote_stream(
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'option',
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await feed.mod.option_quoter(feed.client, symbols)
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)
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# update map from each symbol to requesting client's chan
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await modify_quote_stream(broker, feed_type, symbols, chan, cid)
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try:
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if not feed.tasks.get(feed_type):
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# update map from each symbol to requesting client's chan
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modify_quote_stream(broker, feed_type, symbols, chan, cid)
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# event indicating that task was started and then killed
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task_is_dead = feed.tasks.get(feed_type)
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if task_is_dead is False:
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task_is_dead = trio.Event()
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task_is_dead.set()
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feed.tasks[feed_type] = task_is_dead
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if not task_is_dead.is_set():
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# block and let existing feed task deliver
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# stream data until it is cancelled in which case
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# we'll take over and spawn it again
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await task_is_dead.wait()
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# client channel was likely disconnected
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# but we still want to keep the broker task
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# alive if there are other consumers (including
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# ourselves)
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if any(symbols2chans.values()):
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log.warn(
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f"Data feed task for {feed.mod.name} was cancelled but"
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f" there are still active clients, respawning")
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# no data feeder task yet; so start one
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respawn = True
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log.info(f"Spawning data feed task for {feed.mod.name}")
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while respawn:
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respawn = False
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log.info(f"Spawning data feed task for {feed.mod.name}")
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try:
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async with trio.open_nursery() as nursery:
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nursery.start_soon(
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@ -355,20 +383,28 @@ async def start_quote_stream(
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fan_out_to_chans, feed, get_quotes,
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symbols2chans,
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diff_cached=diff_cached,
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cid=cid
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cid=cid,
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rate=rate,
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)
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)
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feed.tasks[feed_type] = True
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# it's alive!
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task_is_dead.clear()
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except trio.BrokenResourceError:
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log.exception("Respawning failed data feed task")
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respawn = True
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# unblocks when no more symbols subscriptions exist and the
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# quote streamer task terminates (usually because another call
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# was made to `modify_quoter` to unsubscribe from streaming
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# symbols)
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finally:
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log.info(f"Terminated {feed_type} quoter task for {feed.mod.name}")
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feed.tasks.pop(feed_type)
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task_is_dead.set()
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# if we're cancelled externally unsubscribe our quote feed
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modify_quote_stream(broker, feed_type, [], chan, cid)
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# if there are truly no more subscriptions with this broker
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# drop from broker subs dict
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if not any(symbols2chans.values()):
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