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@blink1073
Last active Mar 24, 2022
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Wrap an Asynchronous Class
import asyncio
import atexit
import functools
import inspect
import threading
from concurrent.futures import wait
from typing import Optional
class TaskRunner:
"""A singleton task runner that runs an asyncio event loop on a background thread."""
__instance = None
@staticmethod
def getInstance():
if TaskRunner.__instance is None:
TaskRunner()
assert TaskRunner.__instance is not None
return TaskRunner.__instance
def __init__(self):
if TaskRunner.__instance is not None:
raise Exception("This class is a singleton!")
else:
TaskRunner.__instance = self
self.__io_loop: Optional[asyncio.AbstractEventLoop] = None
self.__runner_thread: Optional[threading.Thread] = None
self.__lock = threading.Lock()
atexit.register(self._close)
def _close(self):
if self.__io_loop:
self.__io_loop.stop()
def _runner(self):
loop = self.__io_loop
assert loop is not None
try:
loop.run_forever()
finally:
loop.close()
def run(self, coro):
"""Synchronously run a coroutine on a background thread."""
with self.__lock:
if self.__io_loop is None:
self.__io_loop = asyncio.new_event_loop()
self.__runner_thread = threading.Thread(target=self._runner, daemon=True)
self.__runner_thread.start()
fut = asyncio.run_coroutine_threadsafe(coro, self.__io_loop)
wait([fut])
return fut.result()
def synchronize_method(async_method, doc=None):
"""Decorate `async_method` so it runs synchronously.
The method runs on an event loop.
:Parameters:
- `async_method`: Unbound method of pymongo Collection, Database,
MongoClient, etc.
- `doc`: Optionally override async_method's docstring
"""
@functools.wraps(async_method)
def method(self, *args, **kwargs):
runner = TaskRunner.getInstance()
coro = async_method(self, *args, **kwargs)
return runner.run(coro)
# This is for the benefit of generating documentation with Sphinx.
method.is_sync_method = True # type: ignore[attr-defined]
if doc is not None:
method.__doc__ = doc
return method
def synchronize_class(kls):
"""Create a synchronous class from an asynchronous one."""
name = kls.__name__.replace("Async", "")
subclass = type(name, (kls,), {})
subclass._async_marker = False
for name in dir(subclass):
if name.startswith('_'):
continue
obj = getattr(subclass, name)
if inspect.iscoroutinefunction(obj):
setattr(subclass, name, synchronize_method(obj))
return subclass
class AsyncMongoClient:
_async_marker = True
async def find_one(self):
kls = AsyncCursor if self._async_marker else Cursor
return kls()
class AsyncCursor:
_async_marker = True
def __iter__(self):
return self
def __next__(self):
raise StopIteration
async def __aiter__(self):
return self
async def __anext__(self):
raise StopAsyncIteration
async def fetch_something(self):
return 'foo'
MongoClient = synchronize_class(AsyncMongoClient)
Cursor = synchronize_class(AsyncCursor)
client = MongoClient()
print(client)
cursor = client.find_one()
print(cursor.fetch_something())
for item in cursor:
print(item)
print(cursor)
print(str(cursor))
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