feat: implement on ending in span processor

CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - docs: Added sqlcommenter example
   ([#4734](https://github.com/open-telemetry/opentelemetry-python/pull/4734))
+- feat: implement on ending in span processor
+  ([#4775](https://github.com/open-telemetry/opentelemetry-python/pull/4775))
 
 ## Version 1.38.0/0.59b0 (2025-10-16)
 

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

@@ -113,6 +113,16 @@ def on_start(
             parent_context: The parent context of the span that just started.
         """
 
+    def _on_ending(self, span: "Span") -> None:
+        """Called when a :class:`opentelemetry.trace.Span` is ending.
+
+        This method is called synchronously on the thread that ends the
+        span, therefore it should not block or throw an exception.
+
+        Args:
+            span: The :class:`opentelemetry.trace.Span` that is ending.
+        """
+
     def on_end(self, span: "ReadableSpan") -> None:
         """Called when a :class:`opentelemetry.trace.Span` is ended.
 
@@ -170,6 +180,10 @@ def on_start(
         for sp in self._span_processors:
             sp.on_start(span, parent_context=parent_context)
 
+    def _on_ending(self, span: "Span") -> None:
+        for sp in self._span_processors:
+            sp._on_ending(span)
+
     def on_end(self, span: "ReadableSpan") -> None:
         for sp in self._span_processors:
             sp.on_end(span)
@@ -254,6 +268,9 @@ def on_start(
             lambda sp: sp.on_start, span, parent_context=parent_context
         )
 
+    def _on_ending(self, span: "Span") -> None:
+        self._submit_and_await(lambda sp: sp._on_ending, span)
+
     def on_end(self, span: "ReadableSpan") -> None:
         self._submit_and_await(lambda sp: sp.on_end, span)
 
@@ -945,6 +962,7 @@ def end(self, end_time: Optional[int] = None) -> None:
 
             self._end_time = end_time if end_time is not None else time_ns()
 
+        self._span_processor._on_ending(self)
         self._span_processor.on_end(self._readable_span())
 
     @_check_span_ended

opentelemetry-sdk/tests/trace/test_span_processor.py

@@ -32,6 +32,10 @@ def span_event_start_fmt(span_processor_name, span_name):
     return span_processor_name + ":" + span_name + ":start"
 
 
+def span_event_ending_fmt(span_processor_name, span_name):
+    return span_processor_name + ":" + span_name + ":ending"
+
+
 def span_event_end_fmt(span_processor_name, span_name):
     return span_processor_name + ":" + span_name + ":end"
 
@@ -50,6 +54,11 @@ def on_end(self, span: "trace.Span") -> None:
         self.span_list.append(span_event_end_fmt(self.name, span.name))
 
 
+class MyExtendedSpanProcessor(MySpanProcessor):
+    def _on_ending(self, span: "trace.Span") -> None:
+        self.span_list.append(span_event_ending_fmt(self.name, span.name))
+
+
 class TestSpanProcessor(unittest.TestCase):
     def test_span_processor(self):
         tracer_provider = trace.TracerProvider()
@@ -120,6 +129,84 @@ def test_span_processor(self):
         # compare if two lists are the same
         self.assertListEqual(spans_calls_list, expected_list)
 
+    def test_span_processor_with_on_ending(self):
+        tracer_provider = trace.TracerProvider()
+        tracer = tracer_provider.get_tracer(__name__)
+
+        spans_calls_list = []  # filled by MySpanProcessor
+        expected_list = []  # filled by hand
+
+        # Span processors are created but not added to the tracer yet
+        sp1 = MyExtendedSpanProcessor("SP1", spans_calls_list)
+        sp2 = MyExtendedSpanProcessor("SP2", spans_calls_list)
+
+        with tracer.start_as_current_span("foo"):
+            with tracer.start_as_current_span("bar"):
+                with tracer.start_as_current_span("baz"):
+                    pass
+
+        # at this point lists must be empty
+        self.assertEqual(len(spans_calls_list), 0)
+
+        # add single span processor
+        tracer_provider.add_span_processor(sp1)
+
+        with tracer.start_as_current_span("foo"):
+            expected_list.append(span_event_start_fmt("SP1", "foo"))
+
+            with tracer.start_as_current_span("bar"):
+                expected_list.append(span_event_start_fmt("SP1", "bar"))
+
+                with tracer.start_as_current_span("baz"):
+                    expected_list.append(span_event_start_fmt("SP1", "baz"))
+
+                expected_list.append(span_event_ending_fmt("SP1", "baz"))
+                expected_list.append(span_event_end_fmt("SP1", "baz"))
+
+            expected_list.append(span_event_ending_fmt("SP1", "bar"))
+            expected_list.append(span_event_end_fmt("SP1", "bar"))
+
+        expected_list.append(span_event_ending_fmt("SP1", "foo"))
+        expected_list.append(span_event_end_fmt("SP1", "foo"))
+
+        self.assertListEqual(spans_calls_list, expected_list)
+
+        spans_calls_list.clear()
+        expected_list.clear()
+
+        # go for multiple span processors
+        tracer_provider.add_span_processor(sp2)
+
+        with tracer.start_as_current_span("foo"):
+            expected_list.append(span_event_start_fmt("SP1", "foo"))
+            expected_list.append(span_event_start_fmt("SP2", "foo"))
+
+            with tracer.start_as_current_span("bar"):
+                expected_list.append(span_event_start_fmt("SP1", "bar"))
+                expected_list.append(span_event_start_fmt("SP2", "bar"))
+
+                with tracer.start_as_current_span("baz"):
+                    expected_list.append(span_event_start_fmt("SP1", "baz"))
+                    expected_list.append(span_event_start_fmt("SP2", "baz"))
+
+                expected_list.append(span_event_ending_fmt("SP1", "baz"))
+                expected_list.append(span_event_ending_fmt("SP2", "baz"))
+                expected_list.append(span_event_end_fmt("SP1", "baz"))
+                expected_list.append(span_event_end_fmt("SP2", "baz"))
+
+            expected_list.append(span_event_ending_fmt("SP1", "bar"))
+            expected_list.append(span_event_ending_fmt("SP2", "bar"))
+            expected_list.append(span_event_end_fmt("SP1", "bar"))
+            expected_list.append(span_event_end_fmt("SP2", "bar"))
+
+        expected_list.append(span_event_ending_fmt("SP1", "foo"))
+        expected_list.append(span_event_ending_fmt("SP2", "foo"))
+        expected_list.append(span_event_end_fmt("SP1", "foo"))
+        expected_list.append(span_event_end_fmt("SP2", "foo"))
+
+        # compare if two lists are the same
+        self.assertListEqual(spans_calls_list, expected_list)
+
     def test_add_span_processor_after_span_creation(self):
         tracer_provider = trace.TracerProvider()
         tracer = tracer_provider.get_tracer(__name__)
@@ -176,6 +263,20 @@ def test_on_start(self):
             )
         multi_processor.shutdown()
 
+    def test_on_ending(self):
+        multi_processor = self.create_multi_span_processor()
+
+        mocks = [mock.Mock(spec=trace.SpanProcessor) for _ in range(0, 5)]
+        for mock_processor in mocks:
+            multi_processor.add_span_processor(mock_processor)
+
+        span = self.create_default_span()
+        multi_processor._on_ending(span)
+
+        for mock_processor in mocks:
+            mock_processor._on_ending.assert_called_once_with(span)
+        multi_processor.shutdown()
+
     def test_on_end(self):
         multi_processor = self.create_multi_span_processor()
 

opentelemetry-sdk/tests/trace/test_trace.py

@@ -1428,6 +1428,10 @@ def span_event_start_fmt(span_processor_name, span_name):
     return span_processor_name + ":" + span_name + ":start"
 
 
+def span_event_ending_fmt(span_processor_name, span_name):
+    return span_processor_name + ":" + span_name + ":ending"
+
+
 def span_event_end_fmt(span_processor_name, span_name):
     return span_processor_name + ":" + span_name + ":end"
 
@@ -1442,6 +1446,9 @@ def on_start(
     ) -> None:
         self.span_list.append(span_event_start_fmt(self.name, span.name))
 
+    def _on_ending(self, span: "trace.ReadableSpan") -> None:
+        self.span_list.append(span_event_ending_fmt(self.name, span.name))
+
     def on_end(self, span: "trace.ReadableSpan") -> None:
         self.span_list.append(span_event_end_fmt(self.name, span.name))
 
@@ -1478,10 +1485,13 @@ def test_span_processor(self):
                 with tracer.start_as_current_span("baz"):
                     expected_list.append(span_event_start_fmt("SP1", "baz"))
 
+                expected_list.append(span_event_ending_fmt("SP1", "baz"))
                 expected_list.append(span_event_end_fmt("SP1", "baz"))
 
+            expected_list.append(span_event_ending_fmt("SP1", "bar"))
             expected_list.append(span_event_end_fmt("SP1", "bar"))
 
+        expected_list.append(span_event_ending_fmt("SP1", "foo"))
         expected_list.append(span_event_end_fmt("SP1", "foo"))
 
         self.assertListEqual(spans_calls_list, expected_list)
@@ -1504,12 +1514,18 @@ def test_span_processor(self):
                     expected_list.append(span_event_start_fmt("SP1", "baz"))
                     expected_list.append(span_event_start_fmt("SP2", "baz"))
 
+                expected_list.append(span_event_ending_fmt("SP1", "baz"))
+                expected_list.append(span_event_ending_fmt("SP2", "baz"))
                 expected_list.append(span_event_end_fmt("SP1", "baz"))
                 expected_list.append(span_event_end_fmt("SP2", "baz"))
 
+            expected_list.append(span_event_ending_fmt("SP1", "bar"))
+            expected_list.append(span_event_ending_fmt("SP2", "bar"))
             expected_list.append(span_event_end_fmt("SP1", "bar"))
             expected_list.append(span_event_end_fmt("SP2", "bar"))
 
+        expected_list.append(span_event_ending_fmt("SP1", "foo"))
+        expected_list.append(span_event_ending_fmt("SP2", "foo"))
         expected_list.append(span_event_end_fmt("SP1", "foo"))
         expected_list.append(span_event_end_fmt("SP2", "foo"))
 
@@ -1532,10 +1548,13 @@ def test_add_span_processor_after_span_creation(self):
                     # add span processor after spans have been created
                     tracer_provider.add_span_processor(sp)
 
+                expected_list.append(span_event_ending_fmt("SP1", "baz"))
                 expected_list.append(span_event_end_fmt("SP1", "baz"))
 
+            expected_list.append(span_event_ending_fmt("SP1", "bar"))
             expected_list.append(span_event_end_fmt("SP1", "bar"))
 
+        expected_list.append(span_event_ending_fmt("SP1", "foo"))
         expected_list.append(span_event_end_fmt("SP1", "foo"))
 
         self.assertListEqual(spans_calls_list, expected_list)