Fix use of link.attributes.dropped, which may not exist (#4119)

Author: kevinji

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix use of `link.attributes.dropped`, which may not exist
+  ([#4119](https://github.com/open-telemetry/opentelemetry-python/pull/4119))
 - Running mypy on SDK resources
   ([#4053](https://github.com/open-telemetry/opentelemetry-python/pull/4053))
 - Added py.typed file to top-level module

exporter/opentelemetry-exporter-otlp-proto-common/src/opentelemetry/exporter/otlp/proto/common/_internal/trace_encoder/__init__.py

@@ -157,7 +157,7 @@ def _encode_links(links: Sequence[Link]) -> Sequence[PB2SPan.Link]:
                 trace_id=_encode_trace_id(link.context.trace_id),
                 span_id=_encode_span_id(link.context.span_id),
                 attributes=_encode_attributes(link.attributes),
-                dropped_attributes_count=link.attributes.dropped,
+                dropped_attributes_count=link.dropped_attributes,
                 flags=_span_flags(link.context),
             )
             pb2_links.append(encoded_link)

exporter/opentelemetry-exporter-otlp-proto-grpc/tests/test_otlp_trace_exporter.py

@@ -171,6 +171,7 @@ def setUp(self):
                         "attributes": BoundedAttributes(
                             attributes={"a": 1, "b": False}
                         ),
+                        "dropped_attributes": 0,
                         "kind": OTLPSpan.SpanKind.SPAN_KIND_INTERNAL,  # pylint: disable=no-member
                     }
                 )

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

@@ -84,6 +84,7 @@
 from deprecated import deprecated
 
 from opentelemetry import context as context_api
+from opentelemetry.attributes import BoundedAttributes
 from opentelemetry.context.context import Context
 from opentelemetry.environment_variables import OTEL_PYTHON_TRACER_PROVIDER
 from opentelemetry.trace.propagation import (
@@ -149,6 +150,12 @@ def __init__(
     def attributes(self) -> types.Attributes:
         return self._attributes
 
+    @property
+    def dropped_attributes(self) -> int:
+        if isinstance(self._attributes, BoundedAttributes):
+            return self._attributes.dropped
+        return 0
+
 
 _Links = Optional[Sequence[Link]]
 

opentelemetry-sdk/tests/trace/test_trace.py

@@ -669,6 +669,19 @@ def test_event_dropped_attributes(self):
         event2 = trace.Event("foo2", {"bar2": "baz2"})
         self.assertEqual(event2.dropped_attributes, 0)
 
+    def test_link_dropped_attributes(self):
+        link1 = trace_api.Link(
+            mock.Mock(spec=trace_api.SpanContext),
+            BoundedAttributes(0, attributes={"bar1": "baz1"}),
+        )
+        self.assertEqual(link1.dropped_attributes, 1)
+
+        link2 = trace_api.Link(
+            mock.Mock(spec=trace_api.SpanContext),
+            {"bar2": "baz2"},
+        )
+        self.assertEqual(link2.dropped_attributes, 0)
+
 
 class DummyError(Exception):
     pass
@@ -1897,7 +1910,7 @@ def test_dropped_attributes(self):
         self.assertEqual(2, span.dropped_attributes)
         self.assertEqual(3, span.dropped_events)
         self.assertEqual(2, span.events[0].dropped_attributes)
-        self.assertEqual(2, span.links[0].attributes.dropped)
+        self.assertEqual(2, span.links[0].dropped_attributes)
 
     def _test_span_limits(
         self,