Allow to start_as_current_span with end_on_exit=False

CHANGELOG.md

@@ -34,6 +34,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1285](https://github.com/open-telemetry/opentelemetry-python/pull/1285))
 - Added `__repr__` for `DefaultSpan`, added `trace_flags` to `__repr__` of
   `SpanContext` ([#1485](https://github.com/open-telemetry/opentelemetry-python/pull/1485)])
+- Added `end_on_exit` argument to `start_as_current_span`
+  ([#1519](https://github.com/open-telemetry/opentelemetry-python/pull/1519)])
 
 ### Changed
 - `opentelemetry-exporter-zipkin` Updated zipkin exporter status code and error tag

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

@@ -290,6 +290,7 @@ def start_as_current_span(
         start_time: typing.Optional[int] = None,
         record_exception: bool = True,
         set_status_on_exception: bool = True,
+        end_on_exit: bool = True,
     ) -> typing.Iterator["Span"]:
         """Context manager for creating a new span and set it
         as the current span in this tracer's context.
@@ -396,6 +397,7 @@ def start_as_current_span(
         start_time: typing.Optional[int] = None,
         record_exception: bool = True,
         set_status_on_exception: bool = True,
+        end_on_exit: bool = True,
     ) -> typing.Iterator["Span"]:
         # pylint: disable=unused-argument,no-self-use
         yield INVALID_SPAN

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

@@ -757,6 +757,7 @@ def start_as_current_span(
         start_time: Optional[int] = None,
         record_exception: bool = True,
         set_status_on_exception: bool = True,
+        end_on_exit: bool = True,
     ) -> Iterator[trace_api.Span]:
         span = self.start_span(
             name=name,
@@ -768,7 +769,7 @@ def start_as_current_span(
             record_exception=record_exception,
             set_status_on_exception=set_status_on_exception,
         )
-        with self.use_span(span, end_on_exit=True) as span_context:
+        with self.use_span(span, end_on_exit=end_on_exit) as span_context:
             yield span_context
 
     def start_span(  # pylint: disable=too-many-locals

opentelemetry-sdk/tests/trace/test_trace.py

@@ -446,6 +446,14 @@ def func():
         self.assertIsNotNone(root2.end_time)
         self.assertIsNot(root1, root2)
 
+    def test_start_as_current_span_no_end_on_exit(self):
+        tracer = new_tracer()
+
+        with tracer.start_as_current_span("root", end_on_exit=False) as root:
+            self.assertIsNone(root.end_time)
+
+        self.assertIsNone(root.end_time)
+
     def test_explicit_span_resource(self):
         resource = resources.Resource.create({})
         tracer_provider = trace.TracerProvider(resource=resource)