async request may raise httpx.ReadTimeout on stale connection

[trim21]

I have a asyncio application using httpx as connection pool, the http client is used to send request to a local nginx server with tls enabled.

My application have low traffic and may not use http client for a long time (hours).

And I observe that it may raise httpx.ReadTimeout from httpcore.ReadTimeout for a long time if the client doesn't have any request for a long time.

request -> wait long time-> next request (and the timeout happened here)

http_client = httpx.AsyncClient(
    follow_redirects=False,
    headers={
        "user-agent": "...",
    },
    limits=httpx.Limits(
        max_keepalive_connections=1,
        max_connections=5,
        keepalive_expiry=1,
    ),
)

Traceback (most recent call last):
  File \"/usr/local/lib/python3.10/site-packages/httpx/_transports/default.py\", line 72, in map_httpcore_exceptions
    yield
  File \"/usr/local/lib/python3.10/site-packages/httpx/_transports/default.py\", line 377, in handle_async_request
    resp = await self._pool.handle_async_request(req)
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/connection_pool.py\", line 216, in handle_async_request
    raise exc from None
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/connection_pool.py\", line 196, in handle_async_request
    response = await connection.handle_async_request(
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/connection.py\", line 101, in handle_async_request
    return await self._connection.handle_async_request(request)
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/http11.py\", line 143, in handle_async_request
    raise exc
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/http11.py\", line 113, in handle_async_request
    ) = await self._receive_response_headers(**kwargs)
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/http11.py\", line 186, in _receive_response_headers
    event = await self._receive_event(timeout=timeout)
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_async/http11.py\", line 224, in _receive_event
    data = await self._network_stream.read(
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_backends/anyio.py\", line 32, in read
    with map_exceptions(exc_map):
  File \"/usr/local/lib/python3.10/contextlib.py\", line 153, in __exit__
    self.gen.throw(typ, value, traceback)
  File \"/usr/local/lib/python3.10/site-packages/httpcore/_exceptions.py\", line 14, in map_exceptions
    raise to_exc(exc) from exc
httpcore.ReadTimeout

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File \"/usr/local/lib/python3.10/site-packages/litestar/middleware/_internal/exceptions/middleware.py\", line 159, in __call__
    await self.app(scope, receive, capture_response_started)
  File \"/usr/local/lib/python3.10/site-packages/litestar/routes/http.py\", line 80, in handle
    response = await self._get_response_for_request(
  File \"/usr/local/lib/python3.10/site-packages/litestar/routes/http.py\", line 132, in _get_response_for_request
    return await self._call_handler_function(
  File \"/usr/local/lib/python3.10/site-packages/litestar/routes/http.py\", line 152, in _call_handler_function
    response_data, cleanup_group = await self._get_response_data(
  File \"/usr/local/lib/python3.10/site-packages/litestar/routes/http.py\", line 197, in _get_response_data
    data = await route_handler.fn(**parsed_kwargs)
  File \"/app/server/review.py\", line 73, in review_patch
    await refresh_access_token(request, back_to=f\"/subject/{patch_id}\")
  File \"/app/server/auth.py\", line 228, in refresh_access_token
    res = await http_client.post(
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1905, in post
    return await self.request(
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1585, in request
    return await self.send(request, auth=auth, follow_redirects=follow_redirects)
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1674, in send
    response = await self._send_handling_auth(
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1702, in _send_handling_auth
    response = await self._send_handling_redirects(
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1739, in _send_handling_redirects
    response = await self._send_single_request(request)
  File \"/usr/local/lib/python3.10/site-packages/httpx/_client.py\", line 1776, in _send_single_request
    response = await transport.handle_async_request(request)
  File \"/usr/local/lib/python3.10/site-packages/httpx/_transports/default.py\", line 376, in handle_async_request
    with map_httpcore_exceptions():
  File \"/usr/local/lib/python3.10/contextlib.py\", line 153, in __exit__
    self.gen.throw(typ, value, traceback)
  File \"/usr/local/lib/python3.10/site-packages/httpx/_transports/default.py\", line 89, in map_httpcore_exceptions
    raise mapped_exc(message) from exc
httpx.ReadTimeout

at where await http_client.post("...", headers={...}, data={...})