Fix: Propagate Otel Context to Subscriber Callback if Provided (#1429)

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: abbrowne126

google/cloud/pubsub_v1/open_telemetry/subscribe_opentelemetry.py

@@ -160,7 +160,7 @@ def end_subscribe_scheduler_span(self) -> None:
         assert self._scheduler_span is not None
         self._scheduler_span.end()
 
-    def start_process_span(self) -> None:
+    def start_process_span(self) -> trace.Span:
         assert self._subscribe_span is not None
         tracer = trace.get_tracer(_OPEN_TELEMETRY_TRACER_NAME)
         publish_create_span_link: Optional[trace.Link] = None
@@ -186,6 +186,7 @@ def start_process_span(self) -> None:
             end_on_exit=False,
         ) as process_span:
             self._process_span = process_span
+            return process_span
 
     def end_process_span(self) -> None:
         assert self._process_span is not None
@@ -200,6 +201,13 @@ def add_process_span_event(self, event: str) -> None:
             },
         )
 
+    def __enter__(self) -> trace.Span:
+        return self.start_process_span()
+
+    def __exit__(self, exc_type, exc_val, traceback):
+        if self._process_span:
+            self.end_process_span()
+
 
 def start_modack_span(
     subscribe_span_links: List[trace.Link],

google/cloud/pubsub_v1/subscriber/_protocol/streaming_pull_manager.py

@@ -148,8 +148,10 @@ def _wrap_callback_errors(
     try:
         if message.opentelemetry_data:
             message.opentelemetry_data.end_subscribe_concurrency_control_span()
-            message.opentelemetry_data.start_process_span()
-        callback(message)
+            with message.opentelemetry_data:
+                callback(message)
+        else:
+            callback(message)
     except BaseException as exc:
         # Note: the likelihood of this failing is extremely low. This just adds
         # a message to a queue, so if this doesn't work the world is in an

tests/unit/pubsub_v1/subscriber/test_streaming_pull_manager.py

@@ -2956,10 +2956,10 @@ def test_opentelemetry_subscriber_concurrency_control_span_end(span_exporter):
     streaming_pull_manager._wrap_callback_errors(mock.Mock(), mock.Mock(), msg)
 
     spans = span_exporter.get_finished_spans()
-    assert len(spans) == 1
+    assert len(spans) == 2
 
     concurrency_control_span = spans[0]
-    concurrency_control_span.name == "subscriber concurrency control"
+    assert concurrency_control_span.name == "subscriber concurrency control"
 
 
 def test_opentelemetry_wrap_callback_error(span_exporter):