feature: concurrent Redis consuming

[ryanrain2016]

Describe the bug
It seems tasks don't run in parallel

How to reproduce
Include source code:

import asyncio

from faststream import FastStream
from faststream.redis import RedisBroker
from pydantic import BaseModel

redis_dsn = 'xxxx'
rb = RedisBroker(redis_dsn)

class User(BaseModel):
    name: str
    age: int = 0

@rb.subscriber(list="users")
async def my_listener(user: User):
    await asyncio.sleep(3)
    print(user, 'from faststream')

async def producer():
    for i in range(10):
        await rb.publish(User(name="Bob", age=i), list="users")

async def main():
    await rb.connect()
    asyncio.create_task(producer())
    app = FastStream(rb)
    await app.run()

if __name__ == '__main__':
    asyncio.run(main())

And/Or steps to reproduce the behavior:

run the script above

Expected behavior
task should run in parallel

Observed behavior
task run one after one

[Lancetnik]

Sure, this is how RedisLists pub/sub works - we consumes the one message, process it and then take the next one.
We can figure out about concurrency, but it can leads to undefined consuming logic and I can't promise this feature possibility

[Lancetnik]

Anyway, you can consume messages in batches - it should speed up your services working.

[ryanrain2016]

Anyway, you can consume messages in batches - it should speed up your services working.
Do you mean code like this?

@rb.subscriber(list=ListSub("users", batch=True))
async def my_listener(user: List[User]):
    await asyncio.sleep(3)
    print(user, 'from faststream')

async def producer():
    # for i in range(10):
    #     await rb.publish_batch(User(name="Bob", age=i), list="users")
    await rb.publish_batch(*[User(name="Bob", age=i) for i in range(10)], list="users")

I doesn't work. No message cosumed, with the output below.

2024-06-07 14:24:44,921 INFO     - FastStream app starting...
2024-06-07 14:24:44,921 INFO     - users |            - `MyListener` waiting for messages
2024-06-07 14:24:44,922 INFO     - FastStream app started successfully! To exit, press CTRL+C

[ryanrain2016]

messages in redis like this

[ryanrain2016]

I find a way. Just push the message to taskiq in a faststream task. The taskiq works just as expected.

[Lancetnik]

I don't sure why your batch example doesn't work, but my works as expected:

from faststream import FastStream
from faststream.redis import RedisBroker, ListSub

rb = RedisBroker()
app = FastStream(rb)

@rb.subscriber(list=ListSub("users", batch=True))
async def my_listener(user: list[str]):
    print(user, "from faststream")

@app.after_startup
async def producer():
    await rb.publish_batch(*["bob"] * 10, list="users")

With the output:

2024-06-07 17:59:34,313 INFO     - FastStream app starting...
2024-06-07 17:59:34,314 INFO     - users |            - `MyListener` waiting for messages
2024-06-07 17:59:34,319 INFO     - FastStream app started successfully! To exit, press CTRL+C
2024-06-07 17:59:34,320 INFO     - users | 34df713e-6 - Received
['bob', 'bob', 'bob', 'bob', 'bob', 'bob', 'bob', 'bob', 'bob', 'bob'] from faststream
2024-06-07 17:59:34,320 INFO     - users | 34df713e-6 - Processed

[Lancetnik]

Anyway, I'll add max_workers option the same with NATS subscriber way to support concurency