How to use asyncio and aioredis lock inside celery tasks?

Question

Goal:

1. Possibility to run asyncio coroutines.
2. Correct celery behavior on exceptions and task retries.
3. Possibility to use aioredis lock.

---

So, how to run async tasks properly to achieve the goal?

What is RuntimeError: await wasn't used with future (below), how can I fix it?

---

I have already tried:

1. asgiref

async_to_sync (from asgiref https://pypi.org/project/asgiref/).

This option makes it possible to run asyncio coroutines, but retries functionality doesn't work.

2. celery-pool-asyncio

(https://pypi.org/project/celery-pool-asyncio/)

Same problem as in asgiref. (This option makes it possible to run asyncio coroutines, but retries functionality doesn't work.)

3. write own async to sync decorator

I have performed try to create my own decorator like async_to_sync that runs coroutines threadsafe (asyncio.run_coroutine_threadsafe), but I have behavior as I described above.

4. asyncio module

Also I have try asyncio.run() or asyncio.get_event_loop().run_until_complete() (and self.retry(...)) inside celery task. This works well, tasks runs, retries works, but there is incorrect coroutine execution - inside async function I cannot use aioredis.

Implementation notes:

• start celery command: celery -A celery_test.celery_app worker -l info -n worker1 -P gevent --concurrency=10 --without-gossip --without-mingle
• celery app:

transport = f"redis://localhost/9"
celery_app = Celery("worker", broker=transport, backend=transport,
                    include=['tasks'])

celery_app.conf.broker_transport_options = {
    'visibility_timeout': 60 * 60 * 24,
    'fanout_prefix': True,
    'fanout_patterns': True
}

• utils:

@contextmanager
def temp_asyncio_loop():
    # asyncio.get_event_loop() automatically creates event loop only for main thread
    try:
        prev_loop = asyncio.get_event_loop()
    except RuntimeError:
        prev_loop = None
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)
    try:
        yield loop
    finally:
        loop.stop()
        loop.close()
        del loop
        asyncio.set_event_loop(prev_loop)


def with_temp_asyncio_loop(f):
    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        with temp_asyncio_loop() as t_loop:
            return f(*args, loop=t_loop, **kwargs)

    return wrapper


def await_(coro):
    return asyncio.get_event_loop().run_until_complete(coro)

• tasks:

@celery_app.task(bind=True, max_retries=30, default_retry_delay=0)
@with_temp_asyncio_loop
def debug(self, **kwargs):
    try:
        await_(debug_async())
    except Exception as exc:
        self.retry(exc=exc)


async def debug_async():
    async with RedisLock(f'redis_lock_{datetime.now()}'):
        pass

• redis lock

class RedisLockException(Exception):
    pass


class RedisLock(AsyncContextManager):
    """
    Redis Lock class

    :param lock_id: string (unique key)
    :param value: dummy value
    :param expire: int (time in seconds that key will storing)
    :param expire_on_delete: int (time in seconds, set pause before deleting)

        Usage:
            try:
                with RedisLock('123_lock', 5 * 60):
                    # do something
            except RedisLockException:
    """

    def __init__(self, lock_id: str, value='1', expire: int = 4, expire_on_delete: int = None):
        self.lock_id = lock_id
        self.expire = expire
        self.value = value
        self.expire_on_delete = expire_on_delete

    async def acquire_lock(self):
        return await redis.setnx(self.lock_id, self.value)

    async def release_lock(self):
        if self.expire_on_delete is None:
            return await redis.delete(self.lock_id)
        else:
            await redis.expire(self.lock_id, self.expire_on_delete)

    async def __aenter__(self, *args, **kwargs):
        if not await self.acquire_lock():
            raise RedisLockException({
                'redis_lock': 'The process: {} still run, try again later'.format(await redis.get(self.lock_id))
            })
        await redis.expire(self.lock_id, self.expire)

    async def __aexit__(self, exc_type, exc_value, traceback):
        await self.release_lock()

On my windows machine await redis.setnx(...) blocks celery worker and it stops producing logs and Ctrl+C doesn't work.

Inside the docker container, I receive an error. There is part of traceback:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/aioredis/connection.py", line 854, in read_response
    response = await self._parser.read_response()
  File "/usr/local/lib/python3.9/site-packages/aioredis/connection.py", line 366, in read_response
    raise ConnectionError(SERVER_CLOSED_CONNECTION_ERROR)
aioredis.exceptions.ConnectionError: Connection closed by server.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/celery/app/trace.py", line 451, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/celery/app/trace.py", line 734, in __protected_call__
    return self.run(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/celery/app/autoretry.py", line 54, in run
    ret = task.retry(exc=exc, **retry_kwargs)
  File "/usr/local/lib/python3.9/site-packages/celery/app/task.py", line 717, in retry
    raise_with_context(exc)
  File "/usr/local/lib/python3.9/site-packages/celery/app/autoretry.py", line 34, in run
    return task._orig_run(*args, **kwargs)
  File "/app/celery_tasks/tasks.py", line 69, in wrapper
    return f(*args, **kwargs) # <--- inside with_temp_asyncio_loop from utils
  ...
  File "/usr/local/lib/python3.9/contextlib.py", line 575, in enter_async_context
    result = await _cm_type.__aenter__(cm)
  File "/app/db/redis.py", line 50, in __aenter__
    if not await self.acquire_lock():
  File "/app/db/redis.py", line 41, in acquire_lock
    return await redis.setnx(self.lock_id, self.value)
  File "/usr/local/lib/python3.9/site-packages/aioredis/client.py", line 1064, in execute_command
    return await self.parse_response(conn, command_name, **options)
  File "/usr/local/lib/python3.9/site-packages/aioredis/client.py", line 1080, in parse_response
    response = await connection.read_response()
  File "/usr/local/lib/python3.9/site-packages/aioredis/connection.py", line 859, in read_response
    await self.disconnect()
  File "/usr/local/lib/python3.9/site-packages/aioredis/connection.py", line 762, in disconnect
    await self._writer.wait_closed()
  File "/usr/local/lib/python3.9/asyncio/streams.py", line 359, in wait_closed
    await self._protocol._get_close_waiter(self)
RuntimeError: await wasn't used with future

• library versions:

celery==5.2.1
aioredis==2.0.0

Answer 1

Use solo pool, then create a decorator which run task function asyncio.get_event_loop().run_until_complete(f(*args, **kwargs)) and make your task asynchronous

def sync(f):
    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        return asyncio.get_event_loop().run_until_complete(f(*args, **kwargs))
    return wrapper

@celery_app.task()
@sync
async def task():
   ...