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devexamples

HTTPX Cache Persistent Offline Replay

Add a persistent caching layer to httpx with httpx-cache, replaying stale responses offline and refreshing in the background.

PythonData Fetching

Code

snippet
import asyncio

import httpx
from httpx_cache import CacheControlTransport

client = httpx.AsyncClient(
    transport=CacheControlTransport(
        cache=httpx_cache.FileCache(cache_dir='.http_cache'),
        cacheable_methods=('GET',),
        cacheable_status_codes=(200, 301, 404),
    )
)


async def fetch_product(product_id: int) -> dict | None:
    try:
        resp = await client.get(f'https://api.example.com/products/{product_id}')
        resp.raise_for_status()
        return resp.json()
    except httpx.HTTPStatusError:
        return None


async def warm_cache(ids: list[int]) -> int:
    results = await asyncio.gather(
        *(fetch_product(pid) for pid in ids),
        return_exceptions=True,
    )
    return sum(1 for r in results if not isinstance(r, Exception))


async def main() -> None:
    await warm_cache(list(range(10)))

    # 断网场景：文件缓存仍可回放此前成功的响应
    product = await fetch_product(3)
    print('served from cache offline:', product is not None)
    await client.aclose()


asyncio.run(main())

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