[monitor opentelemetry exporter] Update maximum size of custom properties

sdk/monitor/azure-monitor-opentelemetry-exporter/CHANGELOG.md

@@ -9,7 +9,8 @@
 ### Bugs Fixed
 
 ### Other Changes
-
+- Update maximum size of custom properties
+([#](https://github.com/Azure/azure-sdk-for-python/pull/))
 - Declare support for Python 3.13 and 3.14
 ([#44550](https://github.com/Azure/azure-sdk-for-python/pull/44550))
 

sdk/monitor/azure-monitor-opentelemetry-exporter/azure/monitor/opentelemetry/exporter/_utils.py

@@ -356,6 +356,7 @@ def _is_any_synthetic_source(properties: Optional[Any]) -> bool:
 
 # pylint: disable=W0622
 def _filter_custom_properties(properties: Attributes, filter=None) -> Dict[str, str]:
+    max_length = 64 * 1024
     truncated_properties: Dict[str, str] = {}
     if not properties:
         return truncated_properties
@@ -365,10 +366,10 @@ def _filter_custom_properties(properties: Attributes, filter=None) -> Dict[str,
             if not filter(key, val):
                 continue
         # Apply truncation rules
-        # Max key length is 150, value is 8192
+        # Max key length is 150, value is 64 * 1024
         if not key or len(key) > 150 or val is None:
             continue
-        truncated_properties[key] = str(val)[:8192]
+        truncated_properties[key] = str(val)[:max_length]
     return truncated_properties
 
 

sdk/monitor/azure-monitor-opentelemetry-exporter/tests/test_utils.py

@@ -35,6 +35,24 @@ class TestUtils(unittest.TestCase):
     def setUp(self):
         self._valid_instrumentation_key = "1234abcd-5678-4efa-8abc-1234567890ab"
 
+    def test_filter_custom_properties_truncates_and_drops_invalid_entries(self):
+        oversized_value = "v" * 9000
+        properties = {
+            "valid_key": oversized_value,
+            "k" * 151: "should_be_dropped",
+            "": "missing_key",
+            "short": "ok",
+            "none_value": None,
+        }
+
+        filtered = _utils._filter_custom_properties(properties)
+
+        self.assertEqual(len(filtered), 2)
+        self.assertIn("valid_key", filtered)
+        self.assertEqual(len(filtered["valid_key"]), 8192)
+        self.assertEqual(filtered["short"], "ok")
+        self.assertNotIn("k" * 151, filtered)
+
     def test_nanoseconds_to_duration(self):
         ns_to_duration = _utils.ns_to_duration
         self.assertEqual(ns_to_duration(0), "0.00:00:00.000")