Config Caching and Retrieving Config Objects

In FastAPI applications, it’s often necessary to load and access configuration settings frequently. To improve performance, you can implement caching mechanisms to avoid redundant configuration loading. This section will explore techniques for caching configuration objects and retrieving them efficiently.

Caching Configuration Objects

Create a Caching Function:

Python

import cachetools

@cachetools.cached(maxsize=128)

def get_settings():

# Load configuration from environment variables or a file

settings = Settings()

return settings

This function uses cachetools to cache the Settings object. The maxsize parameter specifies the maximum number of cached items.

Use the Caching Function in Dependencies:

Python

from fastapi import Depends

def get_settings(settings: Settings = Depends(get_settings)):

return settings

Retrieving Config Objects

To retrieve the cached configuration object, simply call the get_settings function:

Python

@app.get("/")
def read_root(settings: Settings = Depends(get_settings)):
    return {"debug": settings.debug, "database_url": settings.database_url}

Additional Considerations

• Cache Invalidation: If your configuration values change during runtime, you might need to invalidate the cache to ensure that the application uses the latest values. You can use cachetools’ ttl parameter to set a time-to-live for cached items, or manually invalidate the cache when necessary.
• Cache Storage: For more complex caching scenarios, consider using specialized caching libraries like Redis or Memcached. These libraries offer features like distributed caching and persistence.
• Performance Considerations: While caching can improve performance, be mindful of the trade-offs. Caching can introduce complexity and potential issues if not managed properly.

Example with Redis:

Python

import redis
from fastapi import Depends
from cachetools import cached, LRUCache

redis_client = redis.Redis(host="localhost", port=6379)

@cached(cache=LRUCache(maxsize=128), key=lambda: "settings")
def get_settings():
    # Load configuration from environment variables or a file
    settings = Settings()
    redis_client.set("settings", settings.json())
    return settings