Support functools.partial functions in AsyncioInstrumentor.trace_to_thread (#2911)

instrumentation/opentelemetry-instrumentation-asyncio/tests/test_asyncio_to_thread.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import asyncio
+import functools
 import sys
 from unittest import skipIf
 from unittest.mock import patch
@@ -72,3 +73,37 @@ class TestAsyncioToThread(TestBase):
                 for point in metric.data.data_points:
                     self.assertEqual(point.attributes["type"], "to_thread")
                     self.assertEqual(point.attributes["name"], "multiply")
+
+    @skipIf(
+        sys.version_info < (3, 9), "to_thread is only available in Python 3.9+"
+    )
+    def test_to_thread_partial_func(self):
+        def multiply(x, y):
+            return x * y
+
+        double = functools.partial(multiply, 2)
+
+        async def to_thread():
+            result = await asyncio.to_thread(double, 3)
+            assert result == 6
+
+        with self._tracer.start_as_current_span("root"):
+            asyncio.run(to_thread())
+        spans = self.memory_exporter.get_finished_spans()
+
+        self.assertEqual(len(spans), 2)
+        assert spans[0].name == "asyncio to_thread-multiply"
+        for metric in (
+            self.memory_metrics_reader.get_metrics_data()
+            .resource_metrics[0]
+            .scope_metrics[0]
+            .metrics
+        ):
+            if metric.name == "asyncio.process.duration":
+                for point in metric.data.data_points:
+                    self.assertEqual(point.attributes["type"], "to_thread")
+                    self.assertEqual(point.attributes["name"], "multiply")
+            if metric.name == "asyncio.process.created":
+                for point in metric.data.data_points:
+                    self.assertEqual(point.attributes["type"], "to_thread")
+                    self.assertEqual(point.attributes["name"], "multiply")