Asynchronous code failure when connecting to redis

Question

I created a small class to perform basic operations with redis, using aioredis.

class RedisService:
    def __init__(self, r_url) -> str:
        self.redis = r_url

    async def create_connection(self):
        return await aioredis.create_redis(self.redis)

    async def _get(self, key) -> str:
        try:
            return await self.create_connection().get(key, encoding='utf-8')
        finally:
            await self._close()

    async def _set(self, key, value) -> None:
        await self.create_connection().set(key, value)
        await self._close()

    async def _close(self) -> None:
        self.create_connection().close()
        await self._redis.wait_closed() 

And a test handler to call the write/read operation for redis

@router.post('/perform')
async def index():
    key = 'test'
    value = 'test'
    value = await RedisService(r_url)._set(key, value)
    return {'result': value}

But get error

    await self.create_connection.set(key, value)
AttributeError: ''coroutine'' object has no attribute 'set'

I guess the problem could be that the asynchronous code has to be run through an event loop

asyncio.run(some coroutine)

But I can't understand how I can build this logic into my code

Answer 1

Your problem is how you use create_connection. You have to call it and await what it returns.

await self.create_connection()

You’ll then need to await set and get as well. As a one-liner this would get messy.

await (await self.create_connection()).set(key, value)

To help clean this up, you should split the awaits into separate statements.

conn = await self.create_connection()
await conn.set(key, value)

Creating a new connection each time you need to perform an operation can be expensive. I’d recommend changing create_connection in one or two ways.

Either have it attach the connection to your instance

async def create_connection(self):
    self.conn = await aioredis.create_redis(self.redis)

You can call this after you instantiate an instance of RedisService and then use

await self.conn.set(key, value)

Or you can switch to using a connection pool.

async def create_connection(self):
    return await aioredis.create_redis_pool(self.redis)