FastAPI yana goyan jiya da async def da regular def kaɗai don ayyukan hanya. Zaɓin yake mahalaci don aiki: yi amfani da async def lokacin da za ka iya non-blocking I/O, da na yau da kullun lokacin da kodanki ya kira ayyukan da ke toshe (synchronous).
awaitdef@app.get("/async")
async def async_endpoint():
data = await fetch_from_api() # await non-blocking I/O — efficient
return data
@app.get("/sync")
def sync_endpoint():
data = blocking_db_call() # ordinary blocking code
return data
async def → runs on the main event loop. Efficient ONLY if you await non-blocking calls.
⚠️ A BLOCKING call inside async def blocks the WHOLE event loop → kills concurrency!
def → FastAPI runs it in a THREAD POOL, so blocking code doesn't block the event loop.
Safe for synchronous/blocking libraries.
# ✅ async def — when you can await async libraries (httpx, async DB drivers)
async def get_user():
async with httpx.AsyncClient() as c:
return await c.get(url)
# ✅ plain def — when using SYNCHRONOUS/blocking libraries (requests, sync ORM)
def get_user():
return requests.get(url).json() # blocking → FastAPI runs it in a thread
# ❌ THE DANGEROUS MISTAKE — blocking call inside async def
async def bad():
return requests.get(url).json() # blocks the event loop! Use `def` or an async client
Mahalaccing tsari: kada ka saka kiran da ke toshe a cikin async def — yana toshe event loop kuma yana lalata haɗin gida. Kai amfani da async library tare da await, ko yi amfani da sauƙaƙƙen def (wanda FastAPI ke gutsewa a cikin thread pool).
Zaɓi tsakanin async def da def a hanya daidai yana tasiri aiki da haɗin gida na API, kuma yi lokaci a hanya mara kyau babbar kuskure ne.
Sakamakon kawo shine async def kawai yana aiki lokacin da ka await non-blocking ayyuka — saka kira toshe (kamar yadda sync requests library ko driver database toshe) a cikin async def yana toshe duk event loop, yana damje duk bukattuwa masu samuwa kuma yana lalata burin async.
A faɗi, FastAPI a hankali yana aiki sauƙaƙƙe def endpoints a thread pool, don haka code sync/toshe yana amince a can.
Ganewa tsarin nan — yi amfani da async def tare da libraries na ainihi async, yi amfani da sauƙaƙƙen def don code toshe, kuma kada ka ragaba duk toshe kira a cikin async def — ya zama mahalaci don rubuta aiki FastAPI endpoints kuma kaucewa sabawa kaɗan amma mummunan kuskure na buƙatar a sauke jerin bukattuwa a bayan event loop toshe.