العملاء الخارجيون وميزانية التزامن

from contextlib import asynccontextmanager
import httpx
from fastapi import FastAPI, HTTPException
from fastapi.testclient import TestClient
def upstream(request):
    if request.url.path == "/fail":
        raise httpx.ReadTimeout("synthetic timeout", request=request)
    return httpx.Response(200, json={"id": 1})
@asynccontextmanager
async def lifespan(app):
    async with httpx.AsyncClient(transport=httpx.MockTransport(upstream), base_url="https://upstream.example.invalid") as client:
        app.state.upstream = client
        yield
app = FastAPI(lifespan=lifespan)
@app.get("/proxy/{key}")
async def proxy(key: str):
    try:
        response = await app.state.upstream.get("/" + key)
    except httpx.TimeoutException:
        raise HTTPException(status_code=503, detail="Dependency timeout")
    return response.json()
with TestClient(app) as client:
    print(client.get("/proxy/item").json())
    print(client.get("/proxy/fail").status_code)

{'id': 1}
503

يوفر النقل النجاح أوالمهلة داخليا وتترجم 503 وتغلق بالحياة.

import asyncio
async def main():
    gate = asyncio.Semaphore(2)
    state = {"active": 0, "peak": 0}
    async def work(value):
        async with gate:
            state["active"] += 1
            state["peak"] = max(state["peak"], state["active"])
            try:
                await asyncio.sleep(0)
                return value * 2
            finally:
                state["active"] -= 1
    values = await asyncio.gather(*(work(value) for value in [1, 2, 3, 4]))
    print(values, state["peak"])
asyncio.run(main())

[2, 4, 6, 8] 2

تصل المحاكاة لاثنين وتحفظ الترتيب دون شبكة أومولد أوقاعدة أوقياس إنتاجية.