fastapi-cache

Introduction

fastapi-cache is a tool to cache fastapi response and function result, with backends support redis, memcache, and dynamodb.

Features

• Support redis, memcache, dynamodb, and in-memory backends.
• Easily integration with fastapi.
• Support http cache like ETag and Cache-Control.

Requirements

• asyncio environment.
• redis if use RedisBackend.
• memcache if use MemcacheBackend.
• aiobotocore if use DynamoBackend.

Install

> pip install fastapi-cache2

or

> pip install "fastapi-cache2[redis]"

or

> pip install "fastapi-cache2[memcache]"

or

> pip install "fastapi-cache2[dynamodb]"

Usage

Quick Start

from fastapi import FastAPI
from starlette.requests import Request
from starlette.responses import Response

from fastapi_cache import FastAPICache
from fastapi_cache.backends.redis import RedisBackend
from fastapi_cache.decorator import cache

from redis import asyncio as aioredis

app = FastAPI()


@cache()
async def get_cache():
    return 1


@app.get("/")
@cache(expire=60)
async def index():
    return dict(hello="world")


@app.on_event("startup")
async def startup():
    redis = aioredis.from_url("redis://localhost")
    FastAPICache.init(RedisBackend(redis), prefix="fastapi-cache")

Initialization

Firstly you must call FastAPICache.init on startup event of fastapi, there are some global config you can pass in.

Use cache decorator

If you want cache fastapi response transparently, you can use cache as decorator between router decorator and view function and must pass request as param of view function.

Parameter	type, description
expire	int, states a caching time in seconds
namespace	str, namespace to use to store certain cache items
coder	which coder to use, e.g. JsonCoder
key_builder	which key builder to use, default to builtin
injected_dependency_namespace	prefix for injected dependency keywords, defaults to __fastapi_cache.
cache_status_header	Name for the header on the response indicating if the request was served from cache; either HIT or MISS. Defaults to X-FastAPI-Cache.

You can also use cache as decorator like other cache tools to cache common function result.

Injected Request and Response dependencies

The cache decorator adds dependencies for the Request and Response objects, so that it can add cache control headers to the outgoing response, and return a 304 Not Modified response when the incoming request has a matching If-Non-Match header. This only happens if the decorated endpoint doesn't already list these objects directly.

The keyword arguments for these extra dependencies are named __fastapi_cache_request and __fastapi_cache_response to minimize collisions. Use the injected_dependency_namespace argument to @cache() to change the prefix used if those names would clash anyway.

Supported data types

When using the (default) JsonCoder, the cache can store any data type that FastAPI can convert to JSON, including Pydantic models and dataclasses, provided that your endpoint has a correct return type annotation, unless the return type is a standard JSON-supported type such as a dictionary or a list.

E.g. for an endpoint that returns a Pydantic model named SomeModel:

from .models import SomeModel, create_some_model

@app.get("/foo")
@cache(expire=60)
async def foo() -> SomeModel:
    return create_some_model

It is not sufficient to configure a response model in the route decorator; the cache needs to know what the method itself returns.

If no return type decorator is given, the primitive JSON type is returned instead.

For broader type support, use the fastapi_cache.coder.PickleCoder or implement a custom coder (see below).

Custom coder

By default use JsonCoder, you can write custom coder to encode and decode cache result, just need inherit fastapi_cache.coder.Coder.

@app.get("/")
@cache(expire=60, coder=JsonCoder)
async def index():
    return dict(hello="world")

Custom key builder

By default use builtin key builder, if you need, you can override this and pass in cache or FastAPICache.init to take effect globally.

def my_key_builder(
        func,
        namespace: str = "",
        request: Request = None,
        response: Response = None,
        *args,
        **kwargs,
):
    prefix = FastAPICache.get_prefix()
    cache_key = f"{prefix}:{namespace}:{func.__module__}:{func.__name__}:{args}:{kwargs}"
    return cache_key


@app.get("/")
@cache(expire=60, coder=JsonCoder, key_builder=my_key_builder)
async def index():
    return dict(hello="world")

InMemoryBackend

InMemoryBackend store cache data in memory and use lazy delete, which mean if you don't access it after cached, it will not delete automatically.

RedisBackend

When using the redis backend, please make sure you pass in a redis client that does not decode responses (decode_responses must be False, which is the default). Cached data is stored as bytes (binary), decoding these i the redis client would break caching.

Tests and coverage

coverage run -m pytest
coverage html
xdg-open htmlcov/index.html

License

This project is licensed under the Apache-2.0 License.