how to set batch size for kafka batch Subscriber?

[willnufe]

Dear Team,
I saw from the documents that Kafka can consume messages in batches, but what is the maximum batch size, or how to configure it? RabbitMQ can control the maximum number of messages consumed simultaneously via the max_consumers parameter. Does Kafka have similar parameters?

from typing import List

from pydantic import BaseModel, Field

from faststream import FastStream, Logger
from faststream.kafka import KafkaBroker

broker = KafkaBroker("localhost:9092")
app = FastStream(broker)


class HelloWorld(BaseModel):
    msg: str = Field(
        ...,
        examples=["Hello"],
        description="Demo hello world message",
    )


@broker.subscriber("test_batch", batch=True)
async def handle_batch(msg: List[HelloWorld], logger: Logger):
    logger.info(msg)

[Lancetnik]

https://github.com/ag2ai/faststream/blob/main/faststream/kafka/broker/registrator.py#L348-L351