假設通過 httpx.Client 設置 limit 速率控制后，同時發起多個請求訪問 youtube。并且由于科學原因一直連接不上
假設一共 4 個連接，max_connection=2，timeout=5s。

• 默認會發生的情況不是前兩個連接 tcp 握手 timeout，后兩個連接再發起連接 timeout。經過 2 * timeout = 10s 后所有連接失敗
• 默認的配置里，一個請求開始 await 后，由于 limits 限制導致在本地等待的時間也算到總 timeout 里，這就會導致經過 1 * timeout = 5s 后，所有連接全 timeout 了

1. 示例代碼

如下示例代碼可以證明該問題：

import asyncio
import logging
import os
from asyncio import tasksimport httpxmax_conn = 2
max_keepalive = max_connproject_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "."))
assets_root = os.path.join(project_root, "assets")
cert_path = os.path.join(assets_root, "cert", "cert.pem")
TIMEOUT = 5logging.basicConfig(level=logging.DEBUG)async def __log_content_length__(response: httpx.Response):"""這是一個事件鉤子函數，用于在 'response' 事件發生時被調用。"""# 優先嘗試從 headers 獲取 Content-Lengthcontent_length_header = response.headers.get("Content-Length")if content_length_header is not None:# 如果 header 存在，直接使用body_length = content_length_headerelse:# 如果 header 不存在，計算實際內容的長度...logging.info(f"<-- Received response: {response.status_code} {response.request.method} {response.url} "f"- Length: {body_length} bytes")async def make_req(client: httpx.AsyncClient, url):try:response = await client.get(url)except httpx.TimeoutException as e:logging.error(f"Timeout while making request to {url}: {e}")return Nonereturn responsedef main():limits = httpx.Limits(max_connections=max_conn,max_keepalive_connections=max_keepalive,)httpx_client = httpx.AsyncClient(timeout=TIMEOUT, limits=limits, event_hooks={"response": [__log_content_length__]}, verify=False)tasks = [make_req(httpx_client, f"https://youtube.com") for i in range(10)]async def runner():await asyncio.gather(*tasks)asyncio.run(runner())if __name__ == "__main__":main()

2. 修復方法

timeout 傳入一個對象關閉 pool 中 wait 計時

 timeout_config = httpx.Timeout(TIMEOUT, pool=None)