Redis Stream Publishing with FastStream#

Publishing Data to Redis Stream#

To publish messages to a Redis Stream, you implement a function that processes the incoming data and applies the @broker.publisher(...) decorator along with the Redis stream name to it. The function will then publish its return value to the specified stream.

1. Create your RedisBroker instance

   1	broker = RedisBroker("redis://localhost:6379")

2. Initiate your FastStream application with the RedisBroker

   1	app = FastStream(broker)

3. Define your data model

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   class Data(BaseModel): data: NonNegativeFloat = Field( ..., examples=[0.5], description="Float data example" )

4. Set up the function for data processing and publishing

   Using the @broker.publisher(...) decorator in conjunction with the @broker.subscriber(...) decorator allows seamless message processing and republishing to a different stream.

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   @broker.subscriber(stream="input-stream") @broker.publisher(stream="output-stream") async def on_input_data(msg: Data) -> Data: return Data(data=msg.data + 1.0)

   By decorating a function with @broker.publisher(...), we tell FastStream to publish the function's returned data to the designated "output stream". The defined function also serves as a subscriber to the "input-stream", thereby setting up a straightforward data pipeline within Redis streams.

Here's the complete example that showcases the use of decorators for both subscribing and publishing to Redis streams:

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from pydantic import BaseModel, Field, NonNegativeFloat

from faststream import FastStream
from faststream.redis import RedisBroker


class Data(BaseModel):
    data: NonNegativeFloat = Field(
        ..., examples=[0.5], description="Float data example"
    )


broker = RedisBroker("redis://localhost:6379")
app = FastStream(broker)


@broker.subscriber(stream="input-stream")
@broker.publisher(stream="output-stream")
async def on_input_data(msg: Data) -> Data:
    return Data(data=msg.data + 1.0)