Fix flush exception thrown when LoggerProvider not configured

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix flush error when no LoggerProvider configured for LoggingHandler
+  ([#3608](https://github.com/open-telemetry/opentelemetry-python/pull/3608))
 - Fix `OTLPMetricExporter` ignores `preferred_aggregation` property
   ([#3603](https://github.com/open-telemetry/opentelemetry-python/pull/3603))
 - Logs: set `observed_timestamp` field

opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/__init__.py

@@ -553,9 +553,10 @@ def emit(self, record: logging.LogRecord) -> None:
 
     def flush(self) -> None:
         """
-        Flushes the logging output.
+        Flushes the logging output. Skip flushing if logger is NoOp.
         """
-        self._logger_provider.force_flush()
+        if not isinstance(self._logger, NoOpLogger):
+            self._logger_provider.force_flush()
 
 
 class Logger(APILogger):

opentelemetry-sdk/tests/logs/test_handler.py

@@ -79,6 +79,19 @@ def test_log_record_emit_noop(self):
             logger.warning("Warning message")
         handler_mock._translate.assert_not_called()
 
+    def test_log_flush_noop(self):
+
+        no_op_logger_provider = NoOpLoggerProvider()
+        no_op_logger_provider.force_flush = Mock()
+
+        logger = get_logger(logger_provider=NoOpLoggerProvider())
+
+        with self.assertLogs(level=logging.WARNING):
+            logger.warning("Warning message")
+
+        logger.handlers[0].flush()
+        no_op_logger_provider.force_flush.assert_not_called()
+
     def test_log_record_no_span_context(self):
         emitter_provider_mock = Mock(spec=LoggerProvider)
         emitter_mock = APIGetLogger(