OTEL attribute count limit not respected, causing columns dropped

CHANGELOG.md

@@ -24,6 +24,8 @@ inject a `requests.Session` or `grpc.ChannelCredentials` object into OTLP export
   ([#4634](https://github.com/open-telemetry/opentelemetry-python/pull/4634))
 - semantic-conventions: Bump to 1.37.0
   ([#4731](https://github.com/open-telemetry/opentelemetry-python/pull/4731))
+- opentelemetry-sdk: fix handling of OTEL_ATTRIBUTE_COUNT_LIMIT in logs
+  ([#4677](https://github.com/open-telemetry/opentelemetry-python/pull/4677))
 - Performance: Cache `importlib_metadata.entry_points`
   ([#4735](https://github.com/open-telemetry/opentelemetry-python/pull/4735))
 - opentelemetry-sdk: fix calling Logger.emit with an API LogRecord instance

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

@@ -104,7 +104,7 @@ class LogLimits:
     This class does not enforce any limits itself. It only provides a way to read limits from env,
     default values and from user provided arguments.
 
-    All limit arguments must be either a non-negative integer, ``None`` or ``LogLimits.UNSET``.
+    All limit arguments must be either a non-negative integer or ``None``.
 
     - All limit arguments are optional.
     - If a limit argument is not set, the class will try to read its value from the corresponding
@@ -126,8 +126,6 @@ class LogLimits:
             the specified length will be truncated.
     """
 
-    UNSET = -1
-
     def __init__(
         self,
         max_attributes: int | None = None,
@@ -156,9 +154,6 @@ def __repr__(self):
     def _from_env_if_absent(
         cls, value: int | None, env_var: str, default: int | None = None
     ) -> int | None:
-        if value == cls.UNSET:
-            return None
-
         err_msg = "{} must be a non-negative integer but got {}"
 
         # if no value is provided for the limit, try to load it from env
@@ -181,12 +176,6 @@ def _from_env_if_absent(
         return value
 
 
-_UnsetLogLimits = LogLimits(
-    max_attributes=LogLimits.UNSET,
-    max_attribute_length=LogLimits.UNSET,
-)
-
-
 class LogRecord(APILogRecord):
     """A LogRecord instance represents an event being logged.
 
@@ -206,7 +195,7 @@ def __init__(
         body: AnyValue | None = None,
         resource: Resource | None = None,
         attributes: _ExtendedAttributes | None = None,
-        limits: LogLimits | None = _UnsetLogLimits,
+        limits: LogLimits | None = None,
         event_name: str | None = None,
     ): ...
 
@@ -226,7 +215,7 @@ def __init__(
         body: AnyValue | None = None,
         resource: Resource | None = None,
         attributes: _ExtendedAttributes | None = None,
-        limits: LogLimits | None = _UnsetLogLimits,
+        limits: LogLimits | None = None,
     ): ...
 
     def __init__(  # pylint:disable=too-many-locals
@@ -242,7 +231,7 @@ def __init__(  # pylint:disable=too-many-locals
         body: AnyValue | None = None,
         resource: Resource | None = None,
         attributes: _ExtendedAttributes | None = None,
-        limits: LogLimits | None = _UnsetLogLimits,
+        limits: LogLimits | None = None,
         event_name: str | None = None,
     ):
         if trace_id or span_id or trace_flags:
@@ -258,6 +247,10 @@ def __init__(  # pylint:disable=too-many-locals
         span = get_current_span(context)
         span_context = span.get_span_context()
 
+        # Use default LogLimits if none provided
+        if limits is None:
+            limits = LogLimits()
+
         super().__init__(
             **{
                 "timestamp": timestamp,

opentelemetry-sdk/tests/logs/test_handler.py

@@ -27,14 +27,15 @@
     LoggingHandler,
     LogRecordProcessor,
 )
+from opentelemetry.sdk.environment_variables import OTEL_ATTRIBUTE_COUNT_LIMIT
 from opentelemetry.semconv._incubating.attributes import code_attributes
 from opentelemetry.semconv.attributes import exception_attributes
 from opentelemetry.trace import (
     INVALID_SPAN_CONTEXT,
     set_span_in_context,
 )
 
-
+# pylint: disable=too-many-public-methods
 class TestLoggingHandler(unittest.TestCase):
     def test_handler_default_log_level(self):
         processor, logger = set_up_test_logging(logging.NOTSET)
@@ -367,6 +368,111 @@ def test_handler_root_logger_with_disabled_sdk_does_not_go_into_recursion_error(
 
         self.assertEqual(processor.emit_count(), 0)
 
+    @patch.dict(os.environ, {OTEL_ATTRIBUTE_COUNT_LIMIT: "3"})
+    def test_otel_attribute_count_limit_respected_in_logging_handler(self):
+        """Test that OTEL_ATTRIBUTE_COUNT_LIMIT is properly respected by LoggingHandler."""
+        # Create a new LoggerProvider within the patched environment
+        # This will create LogLimits() that reads from the environment variable
+        logger_provider = LoggerProvider()
+        processor = FakeProcessor()
+        logger_provider.add_log_record_processor(processor)
+        logger = logging.getLogger("env_test")
+        handler = LoggingHandler(
+            level=logging.WARNING, logger_provider=logger_provider
+        )
+        logger.addHandler(handler)
+
+        # Create a log record with many extra attributes
+        extra_attrs = {f"custom_attr_{i}": f"value_{i}" for i in range(10)}
+
+        with self.assertLogs(level=logging.WARNING):
+            logger.warning(
+                "Test message with many attributes", extra=extra_attrs
+            )
+
+        log_record = processor.get_log_record(0)
+
+        # With OTEL_ATTRIBUTE_COUNT_LIMIT=3, should have exactly 3 attributes
+        total_attrs = len(log_record.attributes)
+        self.assertEqual(
+            total_attrs,
+            3,
+            f"Should have exactly 3 attributes due to limit, got {total_attrs}",
+        )
+
+        # Should have 10 dropped attributes (10 custom + 3 code - 3 kept = 10 dropped)
+        self.assertEqual(
+            log_record.dropped_attributes,
+            10,
+            f"Should have 10 dropped attributes, got {log_record.dropped_attributes}",
+        )
+
+    @patch.dict(os.environ, {OTEL_ATTRIBUTE_COUNT_LIMIT: "5"})
+    def test_otel_attribute_count_limit_includes_code_attributes(self):
+        """Test that OTEL_ATTRIBUTE_COUNT_LIMIT applies to all attributes including code attributes."""
+        # Create a new LoggerProvider within the patched environment
+        # This will create LogLimits() that reads from the environment variable
+        logger_provider = LoggerProvider()
+        processor = FakeProcessor()
+        logger_provider.add_log_record_processor(processor)
+        logger = logging.getLogger("env_test_2")
+        handler = LoggingHandler(
+            level=logging.WARNING, logger_provider=logger_provider
+        )
+        logger.addHandler(handler)
+
+        # Create a log record with some extra attributes
+        extra_attrs = {f"user_attr_{i}": f"value_{i}" for i in range(8)}
+
+        with self.assertLogs(level=logging.WARNING):
+            logger.warning("Test message", extra=extra_attrs)
+
+        log_record = processor.get_log_record(0)
+
+        # With OTEL_ATTRIBUTE_COUNT_LIMIT=5, should have exactly 5 attributes
+        total_attrs = len(log_record.attributes)
+        self.assertEqual(
+            total_attrs,
+            5,
+            f"Should have exactly 5 attributes due to limit, got {total_attrs}",
+        )
+
+        # Should have 6 dropped attributes (8 user + 3 code - 5 kept = 6 dropped)
+        self.assertEqual(
+            log_record.dropped_attributes,
+            6,
+            f"Should have 6 dropped attributes, got {log_record.dropped_attributes}",
+        )
+
+    def test_logging_handler_without_env_var_uses_default_limit(self):
+        """Test that without OTEL_ATTRIBUTE_COUNT_LIMIT, default limit (128) should apply."""
+        processor, logger = set_up_test_logging(logging.WARNING)
+
+        # Create a log record with many attributes (more than default limit of 128)
+        extra_attrs = {f"attr_{i}": f"value_{i}" for i in range(150)}
+
+        with self.assertLogs(level=logging.WARNING):
+            logger.warning(
+                "Test message with many attributes", extra=extra_attrs
+            )
+
+        log_record = processor.get_log_record(0)
+
+        # Should be limited to default limit (128) total attributes
+        total_attrs = len(log_record.attributes)
+        self.assertEqual(
+            total_attrs,
+            128,
+            f"Should have exactly 128 attributes (default limit), got {total_attrs}",
+        )
+
+        # Should have 25 dropped attributes (150 user + 3 code - 128 kept = 25 dropped)
+        self.assertEqual(
+            log_record.dropped_attributes,
+            25,
+            f"Should have 25 dropped attributes, got {log_record.dropped_attributes}",
+        )
+
 
 def set_up_test_logging(level, formatter=None, root_logger=False):
     logger_provider = LoggerProvider()