Fix _connected in grpclib Channel (#54193)

GitOrigin-RevId: 0a65a95df46aeab69b8e614840aeecf726e1886f

Author: thomasjpfan

py/CHANGELOG_DEV.md

@@ -5,6 +5,7 @@
 - Added `Sandbox.logs`(/docs/sdk/py/latest/Sandbox#logs) namespace to retrieve Sandbox entrypoint logs directly from the SDK. The namespace has two different methods, allowing you `fetch()` logs from a specific date/time range, or `tail()` the most recent logs.
 - Added support for setting the default member Role when creating Restricted Environments through the Python SDK and CLI.
 - The `modal` CLI now accepts a global `--profile` option for simpler ad hoc profile selection.
+- Fixed gRPC channels attempting to reuse connections whose underlying transport is closing.
 - `modal environment roles list --exclude-default` and
   `Environment.roles.list(exclude_default=True)` list only users and service users who have been
   directly assigned a role for the Environment.

py/modal/_utils/grpc_utils.py

@@ -152,6 +152,15 @@ async def _create_connection(self) -> H2Protocol:
         )
         return protocol
 
+    @property
+    def _connected(self) -> bool:
+        return (
+            self._protocol is not None
+            # the H2Protocol handler does have connection_lost
+            and not self._protocol.handler.connection_lost  # type: ignore
+            and not self._protocol.connection.is_closing()
+        )
+
     def close(self):
         self.__closed = True
         return super().close()

py/test/grpc_utils_test.py

@@ -2,6 +2,7 @@
 import pytest
 import time
 import urllib.parse
+from unittest import mock
 
 from google.protobuf.any_pb2 import Any
 from grpclib import GRPCError, Status
@@ -393,6 +394,20 @@ async def test_ModalChannel(servicer):
         await client_stub.BlobCreate(req, metadata=metadata)
 
 
+@pytest.mark.asyncio
+def test_modal_channel_connected_checks_transport():
+    channel = ModalChannel()
+    assert not channel._connected
+
+    channel._protocol = mock.Mock()  # type: ignore
+    channel._protocol.handler.connection_lost = False  # type: ignore
+    channel._protocol.connection.is_closing.return_value = False  # type: ignore
+    assert channel._connected
+
+    channel._protocol.connection.is_closing.return_value = True
+    assert not channel._connected
+
+
 @pytest.mark.asyncio
 async def test_create_channel_with_fallbacks_single_url(servicer):
     # With a single URL, the channel is created and connected normally.