Add try except to messaging connection (#345)

Just a try except around the connection attempt. It displays the
failure to connect in the logs but does not fail fast. It allows the
rest of the application setup to complete just without a connection to a
message bus. You can then `crtl+c` to close it.

I was advised to just add this fix until the subprocess work is done
then we can re-address the behaviour we want.

src/blueapi/messaging/stomptemplate.py

@@ -180,12 +180,17 @@ def finished_connecting(_: Frame):
  self._listener.on_disconnected = self._on_disconnected
 
  LOGGER.info("Connecting...")
- self._conn.connect(
- username=self._authentication.username,
- passcode=self._authentication.passcode,
- wait=True,
- )
- connected.wait()
+
+ try:
+ self._conn.connect(
+ username=self._authentication.username,
+ passcode=self._authentication.passcode,
+ wait=True,
+ )
+ connected.wait()
+ except ConnectFailedException as ex:
+ LOGGER.exception(msg="Failed to connect to message bus", exc_info=ex)
+
  self._ensure_subscribed()
 
  def _ensure_subscribed(self, sub_ids: Optional[List[str]] = None) -> None:

tests/messaging/test_stomptemplate.py

@@ -4,7 +4,10 @@
 from typing import Any, Iterable, List, Type
 
 import pytest
+from mock import ANY, MagicMock, patch
 from pydantic import BaseModel, BaseSettings, Field
+from stomp import Connection
+from stomp.exception import ConnectFailedException
 
 from blueapi.config import StompConfig
 from blueapi.messaging import MessageContext, MessagingTemplate, StompMessagingTemplate
@@ -159,6 +162,29 @@ def test_reconnect(template: MessagingTemplate, test_queue: str) -> None:
  assert reply == "ack"
 
 
+@pytest.fixture()
+def failing_template() -> MessagingTemplate:
+ def connection_exception(*args, **kwargs):
+ raise ConnectFailedException
+
+ connection = Connection()
+ connection.connect = MagicMock(side_effect=connection_exception)
+ return StompMessagingTemplate(connection)
+
+
+@pytest.mark.stomp
+def test_failed_connect(failing_template: MessagingTemplate, test_queue: str) -> None:
+ assert not failing_template.is_connected()
+ with patch(
+ "blueapi.messaging.stomptemplate.LOGGER.error", autospec=True
+ ) as mock_logger:
+ failing_template.connect()
+ assert not failing_template.is_connected()
+ mock_logger.assert_called_once_with(
+ "Failed to connect to message bus", exc_info=ANY
+ )
+
+
 @pytest.mark.stomp
 def test_correlation_id(
  template: MessagingTemplate, test_queue: str, test_queue_2: str