86 lines
2.3 KiB
Python
86 lines
2.3 KiB
Python
# piker: trading gear for hackers
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# Copyright (C) Tyler Goodlet (in stewardship for piker0)
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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"""
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Cacheing apis and toolz.
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"""
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from typing import Dict
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from contextlib import asynccontextmanager, AsyncExitStack
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import trio
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from .brokers import get_brokermod
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from .log import get_logger
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log = get_logger(__name__)
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_cache: Dict[str, 'Client'] = {} # noqa
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@asynccontextmanager
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async def open_cached_client(
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brokername: str,
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*args,
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**kwargs,
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) -> 'Client': # noqa
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"""Get a cached broker client from the current actor's local vars.
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If one has not been setup do it and cache it.
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"""
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global _cache
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clients = _cache.setdefault('clients', {'_lock': trio.Lock()})
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# global cache task lock
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lock = clients['_lock']
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client = None
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try:
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log.info(f"Loading existing `{brokername}` client")
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async with lock:
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client = clients[brokername]
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client._consumers += 1
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yield client
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except KeyError:
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log.info(f"Creating new client for broker {brokername}")
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async with lock:
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brokermod = get_brokermod(brokername)
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exit_stack = AsyncExitStack()
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client = await exit_stack.enter_async_context(
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brokermod.get_client()
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)
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client._consumers = 0
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client._exit_stack = exit_stack
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clients[brokername] = client
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yield client
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finally:
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if client is not None:
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# if no more consumers, teardown the client
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client._consumers -= 1
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if client._consumers <= 0:
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await client._exit_stack.aclose()
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