opentelemetry-sdk: sketch of an OpAMP integration

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

@@ -554,6 +554,33 @@ def _import_id_generator(id_generator_name: str) -> IdGenerator:
     raise RuntimeError(f"{id_generator_name} is not an IdGenerator")
 
 
+def _import_opamp() -> Callable[[Resource], None] | None:
+    # this in development, at the moment we are looking for a callable that takes
+    # the resource and instantiate an OpAMP agent.
+    # Since configuration is not specified every implementers may have its own.
+    # Refer to opentelemetry-opamp-client package on how to setup the OpAMP agent.
+    entry_point = None
+    try:
+        entry_point = next(
+            iter(
+                entry_points(
+                    group="_opentelemetry_opamp", name="pre_sdk_init_function"
+                )
+            )
+        )
+        return entry_point.load()
+    except StopIteration:
+        _logger.debug("No OpAMP init function found")
+    except AttributeError as exc:
+        _logger.warning(
+            "Failed to load OpAMP init function from entry point, %s: %s",
+            entry_point,
+            exc,
+        )
+
+    return None
+
+
 def _initialize_components(
     auto_instrumentation_version: str | None = None,
     trace_exporter_names: list[str] | None = None,
@@ -618,6 +645,15 @@ def _initialize_components(
     # from the env variable else defaults to "unknown_service"
     resource = Resource.create(resource_attributes)
 
+    # OpAMP is a system created to configure OpenTelemetry SDKs with a remote config.
+    # This is different than other init helpers because setting up OpAMP requires distro
+    # provided code as it's not strictly specified. We call OpAMP init before other code
+    # because people may want to have it blocking to get an updated config before setting
+    # up the rest of the SDK.
+    _init_opamp = _import_opamp()
+    if _init_opamp is not None:
+        _init_opamp(resource)
+
     _init_tracing(
         exporters=span_exporters,
         id_generator=id_generator,

opentelemetry-sdk/tests/test_configurator.py

@@ -1573,3 +1573,67 @@ def f(x):
         self.assertEqual(logging.config.dictConfig.__name__, "dictConfig")
         self.assertEqual(logging.basicConfig.__name__, "basicConfig")
         self.assertEqual(logging.config.fileConfig.__name__, "fileConfig")
+
+
+class TestOpAMPInit(TestCase):
+    @patch("opentelemetry.sdk._configuration.entry_points")
+    @patch("opentelemetry.sdk._configuration.Resource")
+    def test_init_function_found(self, mock_resource, mock_entry_points):
+        init_function = mock.Mock()
+        mock_entry_points.configure_mock(
+            return_value=[
+                IterEntryPoint("pre_sdk_init_function", init_function)
+            ]
+        )
+
+        _initialize_components(id_generator=1)
+
+        mock_entry_points.assert_has_calls(
+            [
+                mock.call(
+                    group="_opentelemetry_opamp", name="pre_sdk_init_function"
+                )
+            ]
+        )
+        init_function.assert_called_once_with(
+            mock_resource.create.return_value
+        )
+
+    @patch("opentelemetry.sdk._configuration.entry_points")
+    def test_init_function_load_failure(self, mock_entry_points):
+        entry_point_mock = mock.Mock()
+        entry_point_mock.load.side_effect = AttributeError(
+            "module 'foo' has no attribute 'OpampInit'"
+        )
+        mock_entry_points.configure_mock(
+            return_value=[entry_point_mock],
+        )
+        entry_point_mock.__str__ = lambda x: "<EntryPoint>"
+
+        with self.assertLogs(level="WARNING") as cm:
+            _initialize_components(id_generator=1)
+
+        mock_entry_points.assert_has_calls(
+            [
+                mock.call(
+                    group="_opentelemetry_opamp", name="pre_sdk_init_function"
+                )
+            ]
+        )
+
+        self.assertIn(
+            "WARNING:opentelemetry.sdk._configuration:Failed to load OpAMP init function from entry point,"
+            " <EntryPoint>: module 'foo' has no attribute 'OpampInit'",
+            cm.output,
+        )
+
+    @patch("opentelemetry.sdk._configuration.entry_points")
+    def test_init_function_not_found(self, mock_entry_points):
+        mock_entry_points.configure_mock(return_value=[])
+
+        with self.assertLogs(level="DEBUG") as cm:
+            _initialize_components(id_generator=1)
+        self.assertIn(
+            "DEBUG:opentelemetry.sdk._configuration:No OpAMP init function found",
+            cm.output,
+        )