elasticotel/distro: try harder to print the EDOT configuration at startup

Since we rely on the instrumented application logging setup BUT:
- by default the python root logger should be at WARNING level
- the EDOT Configuration dump is at INFO level
- at startup we don't have application logging already setup

So we need to add a temporary logging handler just for printing our config

Author: xrmx

src/elasticotel/distro/config.py

@@ -100,9 +100,17 @@ def log_env_vars(self):
             for k, v in os.environ.items()
             if k.startswith("OTEL_") or k.startswith("ELASTIC_OTEL_")
         ]
+        # we rely on the application setting up logging and we don't want to interfere with that BUT:
+        # - by default the python root logger should be at WARNING level
+        # - the EDOT Configuration dump is at INFO level
+        # - at startup we don't have application logging already setup
+        # So we add a temporary handler just for printing our config
+        handler = logging.StreamHandler()
+        logger.addHandler(handler)
         logger.info("EDOT Configuration")
         for k, v in sorted(env_vars):
             logger.info("%s: %s", k, v)
+        logger.handlers.remove(handler)
 
     def _handle_logging(self):
         # do validation, we only validate logging_level because sampling_rate is handled by the sdk already

tests/integration/test_integration.py

@@ -213,6 +213,19 @@ def test_script():
         self.assertFalse(telemetry["traces"])
         self.assertTrue(telemetry["logs"])
 
+    def test_configuration_dump_at_startup_with_info_level(self):
+        def test_script():
+            pass
+
+        env = {"OTEL_LOG_LEVEL": "info", "OTEL_ENV_VAR": "value"}
+        stdout, stderr, returncode = self.run_script(
+            test_script, environment_variables=env, wrapper_script="opentelemetry-instrument"
+        )
+
+        assert "EDOT Configuration" in stderr
+        assert "OTEL_LOG_LEVEL: info" in stderr
+        assert "OTEL_ENV_VAR: value" in stderr
+
 
 @pytest.mark.integration
 class HTTPIntegrationTestCase(ElasticIntegrationHTTPTestCase):