fastapi_structlog.md

bento_lib – setting up structured logging in FastAPI

Step 1: Replace logger dependency with a structlog.stdlib.BoundLogger:

In your logger dependency definition, replace your get_logger function with something similar to the following (this example was taken from the Reference service):

import structlog

from bento_lib.logging.structured.configure import configure_structlog_from_bento_config, configure_structlog_uvicorn
from fastapi import Depends
from functools import lru_cache
from typing import Annotated

from .config import ConfigDependency
from .constants import BENTO_SERVICE_KIND

__all__ = [
    "get_logger",
    "LoggerDependency",
]


@lru_cache
def get_logger(config: ConfigDependency) -> structlog.stdlib.BoundLogger:
    configure_structlog_from_bento_config(config)
    configure_structlog_uvicorn()  # If using uvicorn to serve the app

    return structlog.stdlib.get_logger(f"{BENTO_SERVICE_KIND}.logger")


LoggerDependency = Annotated[structlog.stdlib.BoundLogger, Depends(get_logger)]

If you type-hint the logger object elsewhere in your service, make sure to change these type hints from logging.Logger to structlog.stdlib.BoundLogger!

Step 2: Configure access logger middleware

In the application main.py or equivalent:

from bento_lib.apps.fastapi import BentoFastAPI
# ...
app = BentoFastAPI(
    # ...
    configure_structlog_access_logger=True,  # Set up custom access log middleware to replace the default Uvicorn one
    # ...
)
# ...

This internally calls build_structlog_fastapi_middleware(...) in bento_lib.logging.structured.fastapi and attaches it as HTTP middleware to the FastAPI application.