Add default and service name to get_aggregated_resource (open-telemetry#2013)

* Add default & service name to resource aggregator

* Aggregator calls Resource.create() to set default attributes

* Allow get aggregated resources to remove defaults

Author: NathanielRN

CHANGELOG.md

@@ -5,7 +5,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.4.0-0.23b0...HEAD)
-- Fix documentation on well known exporters and variable OTEL_TRACES_EXPORTER which were misnamed [#2023](https://github.com/open-telemetry/opentelemetry-python/pull/2023)
+- Fix documentation on well known exporters and variable OTEL_TRACES_EXPORTER which were misnamed
+  ([#2023](https://github.com/open-telemetry/opentelemetry-python/pull/2023))
+- `opentelemetry-sdk` `get_aggregated_resource()` returns default resource and service name
+  whenever called
+  ([#2013](https://github.com/open-telemetry/opentelemetry-python/pull/2013))
 - `opentelemetry-distro` & `opentelemetry-sdk` Moved Auto Instrumentation Configurator code to SDK
   to let distros use its default implementation
   ([#1937](https://github.com/open-telemetry/opentelemetry-python/pull/1937))

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

@@ -291,23 +291,25 @@ def get_aggregated_resources(
     :param timeout: Number of seconds to wait for each detector to return
     :return:
     """
-    final_resource = initial_resource or _EMPTY_RESOURCE
-    detectors = [OTELResourceDetector()] + detectors
+    detectors_merged_resource = initial_resource or Resource.create()
 
     with concurrent.futures.ThreadPoolExecutor(max_workers=4) as executor:
         futures = [executor.submit(detector.detect) for detector in detectors]
         for detector_ind, future in enumerate(futures):
             detector = detectors[detector_ind]
             try:
-                detected_resources = future.result(timeout=timeout)
+                detected_resource = future.result(timeout=timeout)
             # pylint: disable=broad-except
             except Exception as ex:
                 if detector.raise_on_error:
                     raise ex
                 logger.warning(
                     "Exception %s in detector %s, ignoring", ex, detector
                 )
-                detected_resources = _EMPTY_RESOURCE
+                detected_resource = _EMPTY_RESOURCE
             finally:
-                final_resource = final_resource.merge(detected_resources)
-    return final_resource
+                detectors_merged_resource = detectors_merged_resource.merge(
+                    detected_resource
+                )
+
+    return detectors_merged_resource

opentelemetry-sdk/tests/resources/test_resources.py

@@ -230,9 +230,18 @@ def test_invalid_resource_attribute_values(self):
 
     def test_aggregated_resources_no_detectors(self):
         aggregated_resources = resources.get_aggregated_resources([])
-        self.assertEqual(aggregated_resources, resources.Resource.get_empty())
+        self.assertEqual(
+            aggregated_resources,
+            resources._DEFAULT_RESOURCE.merge(
+                resources.Resource(
+                    {resources.SERVICE_NAME: "unknown_service"}, ""
+                )
+            ),
+        )
 
-    def test_aggregated_resources_with_static_resource(self):
+    def test_aggregated_resources_with_default_destroying_static_resource(
+        self,
+    ):
         static_resource = resources.Resource({"static_key": "static_value"})
 
         self.assertEqual(
@@ -280,13 +289,19 @@ def test_aggregated_resources_multiple_detectors(self):
             resources.get_aggregated_resources(
                 [resource_detector1, resource_detector2, resource_detector3]
             ),
-            resources.Resource(
-                {
-                    "key1": "value1",
-                    "key2": "try_to_overwrite_existing_value",
-                    "key3": "try_to_overwrite_existing_value",
-                    "key4": "value4",
-                }
+            resources._DEFAULT_RESOURCE.merge(
+                resources.Resource(
+                    {resources.SERVICE_NAME: "unknown_service"}, ""
+                )
+            ).merge(
+                resources.Resource(
+                    {
+                        "key1": "value1",
+                        "key2": "try_to_overwrite_existing_value",
+                        "key3": "try_to_overwrite_existing_value",
+                        "key4": "value4",
+                    }
+                )
             ),
         )
 
@@ -321,18 +336,30 @@ def test_aggregated_resources_different_schema_urls(self):
             resources.get_aggregated_resources(
                 [resource_detector1, resource_detector2]
             ),
-            resources.Resource(
-                {"key1": "value1", "key2": "value2", "key3": "value3"},
-                "url1",
+            resources._DEFAULT_RESOURCE.merge(
+                resources.Resource(
+                    {resources.SERVICE_NAME: "unknown_service"}, ""
+                )
+            ).merge(
+                resources.Resource(
+                    {"key1": "value1", "key2": "value2", "key3": "value3"},
+                    "url1",
+                )
             ),
         )
         with self.assertLogs(level=ERROR) as log_entry:
             self.assertEqual(
                 resources.get_aggregated_resources(
                     [resource_detector2, resource_detector3]
                 ),
-                resources.Resource(
-                    {"key2": "value2", "key3": "value3"}, "url1"
+                resources._DEFAULT_RESOURCE.merge(
+                    resources.Resource(
+                        {resources.SERVICE_NAME: "unknown_service"}, ""
+                    )
+                ).merge(
+                    resources.Resource(
+                        {"key2": "value2", "key3": "value3"}, "url1"
+                    )
                 ),
             )
             self.assertIn("url1", log_entry.output[0])
@@ -347,14 +374,20 @@ def test_aggregated_resources_different_schema_urls(self):
                         resource_detector1,
                     ]
                 ),
-                resources.Resource(
-                    {
-                        "key1": "value1",
-                        "key2": "try_to_overwrite_existing_value",
-                        "key3": "try_to_overwrite_existing_value",
-                        "key4": "value4",
-                    },
-                    "url1",
+                resources._DEFAULT_RESOURCE.merge(
+                    resources.Resource(
+                        {resources.SERVICE_NAME: "unknown_service"}, ""
+                    )
+                ).merge(
+                    resources.Resource(
+                        {
+                            "key1": "value1",
+                            "key2": "try_to_overwrite_existing_value",
+                            "key3": "try_to_overwrite_existing_value",
+                            "key4": "value4",
+                        },
+                        "url1",
+                    )
                 ),
             )
             self.assertIn("url1", log_entry.output[0])
@@ -366,7 +399,11 @@ def test_resource_detector_ignore_error(self):
         resource_detector.raise_on_error = False
         self.assertEqual(
             resources.get_aggregated_resources([resource_detector]),
-            resources.Resource.get_empty(),
+            resources._DEFAULT_RESOURCE.merge(
+                resources.Resource(
+                    {resources.SERVICE_NAME: "unknown_service"}, ""
+                )
+            ),
         )
 
     def test_resource_detector_raise_error(self):