Unexpected Performance Results: httpx Async Slower than aiohttp and httpx Sync

[brianler]

Asynchronous requests with httpx are much slower than those with aiohttp, and surprisingly, even slower than httpx's synchronous requests.

Test Results:

-> httpx AsyncClient 2.01 s

-> aiohttp AsyncClient 0.36 s

-> httpx Client with asyncio.to_thread 1.46 s

Test Script:

import asyncio
import httpx
import aiohttp
import time


async def ah():
    async with httpx.AsyncClient(timeout=3600) as client:
        response = await client.get('https://connect.rom.miui.com/generate_204')
        print(response.status_code, response.text)


async def aio():
    async with aiohttp.ClientSession(timeout=aiohttp.ClientTimeout(total=3600)) as client:
        async with client.get('https://connect.rom.miui.com/generate_204') as resp:
            data = await resp.text()
            print(resp.status, data)


def ah_sync():
    with httpx.Client(timeout=3600) as client:
        response = client.get('https://connect.rom.miui.com/generate_204')
        print(response.status_code, response.text)


async def mutli_ah():
    tasks = [ah() for _ in range(100)]
    await asyncio.gather(*tasks)


async def mutli_aio():
    tasks = [aio() for _ in range(100)]
    await asyncio.gather(*tasks)


async def mutli_ah_2():
    tasks = [asyncio.to_thread(ah_sync) for _ in range(100)]
    await asyncio.gather(*tasks)


t1 = time.perf_counter()
asyncio.run(mutli_ah())
print('httpx AsyncClient', time.perf_counter() - t1, 's')
# ------------------------------
# asyncio.run(mutli_aio())
# print('aiohttp AsyncClient', time.perf_counter() - t1, 's')
# ------------------------------
# asyncio.run(mutli_ah_2())
# print('httpx Client with asyncio.to_thread', time.perf_counter() - t1)