Append trace ids to the keygrabber's stderr log lines

libby/keygrabber/main.py

@@ -11,6 +11,7 @@
 from collections.abc import Mapping
 from typing import List, Optional
 
+from .. import telemetry
 from ..daemon import DEFAULT_LOG_FORMAT
 from ..errors import LibbyError
 from .daemon import KeygrabberDaemon
@@ -49,7 +50,9 @@ def log_to_stderr() -> None:
     already given the daemon its own handler, and a second one on the root
     logger would print every line twice.
     """
-    logging.basicConfig(level=logging.INFO, format=DEFAULT_LOG_FORMAT)
+    handler = logging.StreamHandler()
+    handler.setFormatter(telemetry.TraceContextFormatter(DEFAULT_LOG_FORMAT))
+    logging.basicConfig(level=logging.INFO, handlers=[handler])
     # pika logs each connection step at INFO, which the transport's
     # once-a-second reconnect loop would turn into a flood during an outage
     logging.getLogger("pika").setLevel(logging.WARNING)

tests/test_daemon_logging.py

@@ -12,7 +12,8 @@
 from typing import Any, Dict, Optional
 from unittest import mock
 
-from libby.daemon import LibbyDaemon
+from libby import telemetry
+from libby.daemon import DEFAULT_LOG_FORMAT, LibbyDaemon
 from libby.keygrabber import main as keygrabber_main
 
 # lasterror is read back from the daemon's own attribute
@@ -87,6 +88,14 @@ def test_leaves_a_configured_logging_section_alone(self):
         """Do not add a root handler that would print every line twice."""
         self._run({"level": "DEBUG"}).assert_not_called()
 
+    def test_stderr_lines_carry_trace_ids(self):
+        """Format stderr with the formatter that appends the active trace ids."""
+        with mock.patch.object(keygrabber_main.logging, "basicConfig") as basic_config:
+            keygrabber_main.log_to_stderr()
+        (handler,) = basic_config.call_args.kwargs["handlers"]
+        self.assertIsInstance(handler.formatter, telemetry.TraceContextFormatter)
+        self.assertEqual(handler.formatter._fmt, DEFAULT_LOG_FORMAT)  # pylint: disable=protected-access
+
     def test_quiets_pika_connection_chatter(self):
         pika = logging.getLogger("pika")
         level = pika.level