opentelemetry-sdk: fix serialization of objects in log handler (open-telemetry#4528)

* opentelemetry-sdk: fix serialization of objects in log handler

We should convert to string objects that are not AnyValues because
otherwise exporter will fail later in the pipeline.
While the export of all AnyValue types is not correct yet, exporter tests
expects to being able to handle them and so they are already used in
the handler.

Author: xrmx

CHANGELOG.md

@@ -20,7 +20,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Patch logging.basicConfig so OTel logs don't cause console logs to disappear
   ([#4436](https://github.com/open-telemetry/opentelemetry-python/pull/4436))
 - Fix ExplicitBucketHistogramAggregation to handle multiple explicit bucket boundaries advisories
- ([#4521](https://github.com/open-telemetry/opentelemetry-python/pull/4521))
+  ([#4521](https://github.com/open-telemetry/opentelemetry-python/pull/4521))
+- opentelemetry-sdk: Fix serialization of objects in log handler
+  ([#4528](https://github.com/open-telemetry/opentelemetry-python/pull/4528))
 
 ## Version 1.31.0/0.52b0 (2025-03-12)
 

opentelemetry-api/src/opentelemetry/attributes/__init__.py

@@ -16,13 +16,24 @@
 import threading
 from collections import OrderedDict
 from collections.abc import MutableMapping
-from typing import Optional, Sequence, Tuple, Union
+from typing import Mapping, Optional, Sequence, Tuple, Union
 
 from opentelemetry.util import types
 
 # bytes are accepted as a user supplied value for attributes but
 # decoded to strings internally.
 _VALID_ATTR_VALUE_TYPES = (bool, str, bytes, int, float)
+# AnyValue possible values
+_VALID_ANY_VALUE_TYPES = (
+    type(None),
+    bool,
+    bytes,
+    int,
+    float,
+    str,
+    Sequence,
+    Mapping,
+)
 
 
 _logger = logging.getLogger(__name__)

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

@@ -36,7 +36,7 @@
     get_logger_provider,
     std_to_otel,
 )
-from opentelemetry.attributes import BoundedAttributes
+from opentelemetry.attributes import _VALID_ANY_VALUE_TYPES, BoundedAttributes
 from opentelemetry.sdk.environment_variables import (
     OTEL_ATTRIBUTE_COUNT_LIMIT,
     OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT,
@@ -523,8 +523,11 @@ def _translate(self, record: logging.LogRecord) -> LogRecord:
             # itself instead of its string representation.
             # For more background, see: https://github.com/open-telemetry/opentelemetry-python/pull/4216
             if not record.args and not isinstance(record.msg, str):
-                # no args are provided so it's *mostly* safe to use the message template as the body
-                body = record.msg
+                #  if record.msg is not a value we can export, cast it to string
+                if not isinstance(record.msg, _VALID_ANY_VALUE_TYPES):
+                    body = str(record.msg)
+                else:
+                    body = record.msg
             else:
                 body = record.getMessage()
 

opentelemetry-sdk/tests/logs/test_handler.py

@@ -153,6 +153,7 @@ def test_log_record_exception(self):
         log_record = processor.get_log_record(0)
 
         self.assertIsNotNone(log_record)
+        self.assertTrue(isinstance(log_record.body, str))
         self.assertEqual(log_record.body, "Zero Division Error")
         self.assertEqual(
             log_record.attributes[SpanAttributes.EXCEPTION_TYPE],
@@ -226,6 +227,40 @@ def test_log_exc_info_false(self):
             SpanAttributes.EXCEPTION_STACKTRACE, log_record.attributes
         )
 
+    def test_log_record_exception_with_object_payload(self):
+        processor, logger = set_up_test_logging(logging.ERROR)
+
+        class CustomException(Exception):
+            def __str__(self):
+                return "CustomException stringified"
+
+        try:
+            raise CustomException("CustomException message")
+        except CustomException as exception:
+            with self.assertLogs(level=logging.ERROR):
+                logger.exception(exception)
+
+        log_record = processor.get_log_record(0)
+
+        self.assertIsNotNone(log_record)
+        self.assertTrue(isinstance(log_record.body, str))
+        self.assertEqual(log_record.body, "CustomException stringified")
+        self.assertEqual(
+            log_record.attributes[SpanAttributes.EXCEPTION_TYPE],
+            CustomException.__name__,
+        )
+        self.assertEqual(
+            log_record.attributes[SpanAttributes.EXCEPTION_MESSAGE],
+            "CustomException message",
+        )
+        stack_trace = log_record.attributes[
+            SpanAttributes.EXCEPTION_STACKTRACE
+        ]
+        self.assertIsInstance(stack_trace, str)
+        self.assertTrue("Traceback" in stack_trace)
+        self.assertTrue("CustomException" in stack_trace)
+        self.assertTrue(__file__ in stack_trace)
+
     def test_log_record_trace_correlation(self):
         processor, logger = set_up_test_logging(logging.WARNING)