Handle explicit end time when ending spans

opentracing-shim/src/opentracingshim/__init__.py

@@ -61,12 +61,11 @@ def set_operation_name(self, operation_name):
         self._otel_span.update_name(operation_name)
         return self
 
-    def finish(self, finish_time=None):
-        self._otel_span.end()
-        # TODO: Handle finish_time. The OpenTelemetry API doesn't currently
-        # support setting end time on a span and we cannot assume that all
-        # OpenTelemetry Tracer implementations have an `end_time` field.
-        # https://github.com/open-telemetry/opentelemetry-python/issues/134
+    def finish(self, finish_time: float = None):
+        end_time = finish_time
+        if end_time is not None:
+            end_time = util.time_seconds_to_ns(finish_time)
+        self._otel_span.end(end_time=end_time)
 
     def set_tag(self, key, value):
         self._otel_span.set_attribute(key, value)

opentracing-shim/tests/test_shim.py

@@ -119,6 +119,16 @@ def test_explicit_start_time(self):
             result = util.time_seconds_from_ns(scope.span.unwrap().start_time)
             self.assertEqual(result, now)
 
+    def test_explicit_end_time(self):
+        """Test `end_time` argument of `finish()` method."""
+
+        span = self.shim.start_span("TestSpan")
+        now = time.time()
+        span.finish(now)
+
+        end_time = util.time_seconds_from_ns(span.unwrap().end_time)
+        self.assertEqual(end_time, now)
+
     def test_explicit_span_activation(self):
         """Test manual activation and deactivation of a span."""