Record exception on context manager exit

This updates the tracer context manager to automatically record
exceptions as events on exit if an exception was raised within the
context manager's context.

Author: owais

Diff for: opentelemetry-sdk/CHANGELOG.md

@@ -6,6 +6,7 @@
   ([#1128](https://github.com/open-telemetry/opentelemetry-python/pull/1128))
 - Add support for `OTEL_BSP_MAX_QUEUE_SIZE`, `OTEL_BSP_SCHEDULE_DELAY_MILLIS`, `OTEL_BSP_MAX_EXPORT_BATCH_SIZE` and `OTEL_BSP_EXPORT_TIMEOUT_MILLIS` environment variables
   ([#1105](https://github.com/open-telemetry/opentelemetry-python/pull/1120))
+- `start_as_current_span` and `use_span` now auto-record any exceptions raised inside the context manager.
 
 ## Version 0.13b0
 

Diff for: opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -705,9 +705,10 @@ def start_as_current_span(
         kind: trace_api.SpanKind = trace_api.SpanKind.INTERNAL,
         attributes: types.Attributes = None,
         links: Sequence[trace_api.Link] = (),
+        record_exception: bool = False
     ) -> Iterator[trace_api.Span]:
         span = self.start_span(name, parent, kind, attributes, links)
-        return self.use_span(span, end_on_exit=True)
+        return self.use_span(span, end_on_exit=True, record_exception=record_exception)
 
     def start_span(  # pylint: disable=too-many-locals
         self,
@@ -786,7 +787,7 @@ def start_span(  # pylint: disable=too-many-locals
 
     @contextmanager
     def use_span(
-        self, span: trace_api.Span, end_on_exit: bool = False
+        self, span: trace_api.Span, end_on_exit: bool = False, record_exception: bool = False
     ) -> Iterator[trace_api.Span]:
         try:
             token = context_api.attach(context_api.set_value(SPAN_KEY, span))
@@ -796,6 +797,8 @@ def use_span(
                 context_api.detach(token)
 
         except Exception as error:  # pylint: disable=broad-except
+            if record_exception:
+                span.record_exception(error)
             if (
                 isinstance(span, Span)
                 and span.status is None

Diff for: opentelemetry-sdk/tests/trace/test_trace.py

@@ -799,6 +799,24 @@ def test_record_exception(self):
             exception_event.attributes["exception.stacktrace"],
         )
 
+    def test_record_exception_context_manager(self):
+        try:
+            with self.tracer.start_as_current_span("span", record_exception=True) as span:
+                raise RuntimeError("example error")
+        except RuntimeError:
+            pass
+        finally:
+            self.assertEqual(len(span.events), 1)
+            event = span.events[0]
+            self.assertEqual("exception", event.name)
+            self.assertEqual("RuntimeError", event.attributes["exception.type"])
+            self.assertEqual("example error", event.attributes["exception.message"])
+
+            stacktrace = '''in test_record_exception_context_manager
+    raise RuntimeError("example error")
+RuntimeError: example error'''
+            self.assertIn(stacktrace, event.attributes["exception.stacktrace"])
+
 
 def span_event_start_fmt(span_processor_name, span_name):
     return span_processor_name + ":" + span_name + ":start"