Fix deadlock bug

Author: DylanRussell

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

@@ -489,6 +489,7 @@ def __init__(
     ) -> None:
         super().__init__(level=level)
         self._logger_provider = logger_provider or get_logger_provider()
+        # self.flushOnClose = False
 
     @staticmethod
     def _get_attributes(record: logging.LogRecord) -> _ExtendedAttributes:
@@ -584,7 +585,8 @@ def flush(self) -> None:
         if hasattr(self._logger_provider, "force_flush") and callable(
             self._logger_provider.force_flush
         ):
-            self._logger_provider.force_flush()
+            thread = threading.Thread(target=self._logger_provider.force_flush)
+            thread.start()
 
 
 class Logger(APILogger):

opentelemetry-sdk/tests/logs/test_handler.py

@@ -59,6 +59,34 @@ def test_handler_custom_log_level(self):
             logger.critical("No Time For Caution")
         self.assertEqual(processor.emit_count(), 2)
 
+    def test_handler_calling_flush_does_not_cause_deadlock(self):
+        class LogProcessorThatAccessesLockOnFlush(LogRecordProcessor):
+            def emit(self, log_data: LogData):
+                pass
+
+            def shutdown(self):
+                pass
+
+            def force_flush(self, timeout_millis: int = 30000):
+                # Deadlock will happen here IF `flush` starts a new thread
+                # and then blocks, if it just starts a thread and then returns
+                # we don't seem to encounter the issue..
+                logging._lock.acquire()
+                # assert logging._lock.acquire(False) is True
+                logging._lock.release()
+
+        logger_provider = LoggerProvider()
+        processor = LogProcessorThatAccessesLockOnFlush()
+        logger_provider.add_log_record_processor(processor)
+        handler = LoggingHandler(logger_provider=logger_provider)
+        logging.getLogger().addHandler(handler)
+        # The below code is essentially recreating what is causing the problem inside
+        # logging.config.dictConfig. Actually calling logging.config.dictConfig will modify
+        # global state inside the logging module and break lots of tests.
+        with logging._lock:
+            for handler in logging.getLogger().handlers:
+                handler.flush()
+
     # pylint: disable=protected-access
     def test_log_record_emit_noop(self):
         noop_logger_provder = NoOpLoggerProvider()