Use ThreadedResolver to honor /etc/hosts and nsswitch.conf

.ci/assets/ci_constraints.txt

@@ -15,5 +15,3 @@ azure-storage-blob!=12.28.*
 # Apparently does not work with current azurite.
 
 
-pycares<5
-# older aiodns versions don't pin pycares UB, and are broken by pycares>=5

pulpcore/download/factory.py

@@ -144,7 +144,13 @@ def _make_aiohttp_session_from_remote(self):
         # I don't see why...
         # https://github.com/aio-libs/aiohttp/pull/3372
         return aiohttp.ClientSession(
-            connector=aiohttp.TCPConnector(loop=asyncio.get_event_loop(), **tcp_conn_opts),
+            # ThreadedResolver uses getaddrinfo() which honors /etc/hosts and nsswitch.conf;
+            # the default AsyncResolver (c-ares) bypasses the system resolver entirely.
+            connector=aiohttp.TCPConnector(
+                loop=asyncio.get_event_loop(),
+                resolver=aiohttp.resolver.ThreadedResolver(loop=asyncio.get_event_loop()),
+                **tcp_conn_opts,
+            ),
             timeout=timeout,
             headers=headers,
             requote_redirect_url=False,

pulpcore/download/http.py

@@ -161,7 +161,9 @@ def __init__(
             self._close_session_on_finalize = False
         else:
             timeout = aiohttp.ClientTimeout(total=None, sock_connect=600, sock_read=600)
-            conn = aiohttp.TCPConnector()
+            # ThreadedResolver uses getaddrinfo() which honors /etc/hosts and nsswitch.conf;
+            # the default AsyncResolver (c-ares) bypasses the system resolver entirely.
+            conn = aiohttp.TCPConnector(resolver=aiohttp.resolver.ThreadedResolver())
             self.session = aiohttp.ClientSession(
                 connector=conn, timeout=timeout, headers=headers, requote_redirect_url=False
             )

pyproject.toml

@@ -25,7 +25,6 @@ classifiers=[
 ]
 requires-python = ">=3.11"
 dependencies = [
-  "aiodns>=3.3.0,<3.7",  # Looks like only bugfixes in z-Stream.
   "aiofiles>=22.1,<=25.1.0",  # Uses sort of CalVer, luckily not released often https://github.com/Tinche/aiofiles/issues/144 .
   "aiohttp>=3.10.10,<3.15",  # SemVer https://docs.aiohttp.org/en/stable/faq.html#what-is-the-api-stability-and-deprecation-policy .
   "asyncio-throttle>=1.0,<=1.0.2",  # Unsure about versioning, but not released often anyway.