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client_multiplexer.py
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client_multiplexer.py
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# Copyright 2020 Google LLC
#
# 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 asyncio
import threading
from typing import Generic, TypeVar, Callable, Dict, Awaitable
_Key = TypeVar("_Key")
_Client = TypeVar("_Client")
class ClientMultiplexer(Generic[_Key, _Client]):
_OpenedClientFactory = Callable[[_Key], _Client]
_ClientCloser = Callable[[_Client], None]
_factory: _OpenedClientFactory
_closer: _ClientCloser
_lock: threading.Lock
_live_clients: Dict[_Key, _Client]
def __init__(
self,
factory: _OpenedClientFactory,
closer: _ClientCloser = lambda client: client.__exit__(None, None, None),
):
self._factory = factory
self._closer = closer
self._lock = threading.Lock()
self._live_clients = {}
def get_or_create(self, key: _Key) -> _Client:
with self._lock:
if key not in self._live_clients:
self._live_clients[key] = self._factory(key)
return self._live_clients[key]
def try_erase(self, key: _Key, client: _Client):
with self._lock:
if key not in self._live_clients:
return
current_client = self._live_clients[key]
if current_client is not client:
return
del self._live_clients[key]
self._closer(client)
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
live_clients: Dict[_Key, _Client]
with self._lock:
live_clients = self._live_clients
self._live_clients = {}
for topic, client in live_clients.items():
self._closer(client)
class AsyncClientMultiplexer(Generic[_Key, _Client]):
_OpenedClientFactory = Callable[[_Key], Awaitable[_Client]]
_ClientCloser = Callable[[_Client], Awaitable[None]]
_factory: _OpenedClientFactory
_closer: _ClientCloser
_live_clients: Dict[_Key, Awaitable[_Client]]
def __init__(
self,
factory: _OpenedClientFactory,
closer: _ClientCloser = lambda client: client.__aexit__(None, None, None),
):
self._factory = factory
self._closer = closer
self._live_clients = {}
async def get_or_create(self, key: _Key) -> _Client:
if key not in self._live_clients:
self._live_clients[key] = asyncio.ensure_future(self._factory(key))
return await self._live_clients[key]
async def try_erase(self, key: _Key, client: _Client):
if key not in self._live_clients:
return
current_client = await self._live_clients[key]
if current_client is not client:
return
# duplicate check after await that no one raced with us
if key not in self._live_clients:
return
del self._live_clients[key]
await self._closer(client)
async def __aenter__(self):
return self
async def __aexit__(self, exc_type, exc_val, exc_tb):
live_clients: Dict[_Key, Awaitable[_Client]]
live_clients = self._live_clients
self._live_clients = {}
for topic, client in live_clients.items():
await self._closer(await client)