Randomly ConnectTimeout instead of ConnectError (Name or service not known)

[powellnorma]

Version 0.25

Hi, not sure if this counts as bug, but I was relying on a ConnectError being thrown that contains the string Name or service not known in case the A-Record was missing, to detect DNS related issues. But in the current case only half the time it works as intended, in the other half a stack trace like below gets thrown.

I do have strict timeout requirements (4 seconds), but I thought that the DNS resolution does not count into ConnectTimeout?
FWIW this ruby library does not count DNS-Delays into ConnectTimeout.

Is there a way to reliably get a ConnectError in such cases? Or maybe we can add a ResolveTimeout? Thank you.

Traceback (most recent call last):
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/anyio/_core/_sockets.py", line 186, in connect_tcp
    addr_obj = ip_address(remote_host)
               ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/ipaddress.py", line 54, in ip_address
    raise ValueError(f'{address!r} does not appear to be an IPv4 or IPv6 address')
ValueError: 'www.domain-has-no-a-record.tld' does not appear to be an IPv4 or IPv6 address

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_backends/anyio.py", line 114, in connect_tcp
    stream: anyio.abc.ByteStream = await anyio.connect_tcp(
                                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/anyio/_core/_sockets.py", line 189, in connect_tcp
    gai_res = await getaddrinfo(
              ^^^^^^^^^^^^^^^^^^
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_exceptions.py", line 10, in map_exceptions
    yield
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_backends/anyio.py", line 113, in connect_tcp
    with anyio.fail_after(timeout):
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/anyio/_core/_tasks.py", line 118, in __exit__
    raise TimeoutError
TimeoutError

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

Traceback (most recent call last):
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_transports/default.py", line 66, in map_httpcore_exceptions
    yield
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_transports/default.py", line 366, in handle_async_request
    resp = await self._pool.handle_async_request(req)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_async/connection_pool.py", line 262, in handle_async_request
    raise exc
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_async/connection_pool.py", line 245, in handle_async_request
    response = await connection.handle_async_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_async/connection.py", line 99, in handle_async_request
    raise exc
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_async/connection.py", line 76, in handle_async_request
    stream = await self._connect(request)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_async/connection.py", line 124, in _connect
    stream = await self._network_backend.connect_tcp(**kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_backends/auto.py", line 31, in connect_tcp
    return await self._backend.connect_tcp(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_backends/anyio.py", line 112, in connect_tcp
    with map_exceptions(exc_map):
  File "/usr/lib64/python3.11/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
    raise to_exc(exc) from exc
httpcore.ConnectTimeout

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

Traceback (most recent call last):
	[..]
    return await client.request(method, url, **opts)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_client.py", line 1530, in request
    return await self.send(request, auth=auth, follow_redirects=follow_redirects)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_client.py", line 1617, in send
    response = await self._send_handling_auth(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_client.py", line 1645, in _send_handling_auth
    response = await self._send_handling_redirects(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_client.py", line 1682, in _send_handling_redirects
    response = await self._send_single_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_client.py", line 1719, in _send_single_request
    response = await transport.handle_async_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_transports/default.py", line 365, in handle_async_request
    with map_httpcore_exceptions():
  File "/usr/lib64/python3.11/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
  File "/home/user/.virtualenvs/venv3.11/lib64/python3.11/site-packages/httpx/_transports/default.py", line 83, in map_httpcore_exceptions
    raise mapped_exc(message) from exc
httpx.ConnectTimeout