opentelemetry-instrumentation-system-metrics: fix cpython metrics (open-telemetry#4092)

* opentelemetry-instrumentation-system-metrics: fix cpython metrics

Use the proper attribute per semantic convention for the generation.
Don't break the backward compatibility for now, add a TODO to remove
the wrong attribute in following releases.

Author: xrmx

CHANGELOG.md

@@ -58,6 +58,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4068](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4068))
 - `opentelemetry-instrumentation-mysqlclient`: Replace SpanAttributes with semconv constants
   ([#4067](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4067))
+- `opentelemetry-instrumentation-system-metrics`: Use proper numeric `cpython.gc.generation` attribute in CPython metrics, out of spec `generation` attribute is deprecated and will be removed in the future
+  ([#4092](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4092))
 
 ## Version 1.39.0/0.60b0 (2025-12-03)
 

instrumentation/opentelemetry-instrumentation-system-metrics/src/opentelemetry/instrumentation/system_metrics/__init__.py

@@ -112,6 +112,9 @@
 from opentelemetry.instrumentation.system_metrics.package import _instruments
 from opentelemetry.instrumentation.system_metrics.version import __version__
 from opentelemetry.metrics import CallbackOptions, Observation, get_meter
+from opentelemetry.semconv._incubating.attributes.cpython_attributes import (
+    CPYTHON_GC_GENERATION,
+)
 from opentelemetry.semconv._incubating.metrics.process_metrics import (
     create_process_cpu_utilization,
 )
@@ -958,6 +961,8 @@ def _get_runtime_gc_collections(
     ) -> Iterable[Observation]:
         """Observer callback for garbage collection"""
         for index, stat in enumerate(gc.get_stats()):
+            self._runtime_gc_collections_labels[CPYTHON_GC_GENERATION] = index
+            # TODO: remove this a few releases after 1.40.0
             self._runtime_gc_collections_labels["generation"] = str(index)
             yield Observation(
                 stat["collections"], self._runtime_gc_collections_labels.copy()
@@ -968,6 +973,10 @@ def _get_runtime_gc_collected_objects(
     ) -> Iterable[Observation]:
         """Observer callback for garbage collection collected objects"""
         for index, stat in enumerate(gc.get_stats()):
+            self._runtime_gc_collected_objects_labels[
+                CPYTHON_GC_GENERATION
+            ] = index
+            # TODO: remove this a few releases after 1.40.0
             self._runtime_gc_collected_objects_labels["generation"] = str(
                 index
             )
@@ -981,6 +990,10 @@ def _get_runtime_gc_uncollectable_objects(
     ) -> Iterable[Observation]:
         """Observer callback for garbage collection uncollectable objects"""
         for index, stat in enumerate(gc.get_stats()):
+            self._runtime_gc_uncollectable_objects_labels[
+                CPYTHON_GC_GENERATION
+            ] = index
+            # TODO: remove this a few releases after 1.40.0
             self._runtime_gc_uncollectable_objects_labels["generation"] = str(
                 index
             )

instrumentation/opentelemetry-instrumentation-system-metrics/tests/test_system_metrics.py

@@ -983,9 +983,15 @@ def test_runtime_get_gc_collections(self, mock_gc_get_stats):
             }
         )
         expected_gc_collections = [
-            _SystemMetricsResult({"generation": "0"}, 10),
-            _SystemMetricsResult({"generation": "1"}, 20),
-            _SystemMetricsResult({"generation": "2"}, 30),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 0, "generation": "0"}, 10
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 1, "generation": "1"}, 20
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 2, "generation": "2"}, 30
+            ),
         ]
         self._test_metrics(
             "cpython.gc.collections",
@@ -1007,9 +1013,15 @@ def test_runtime_get_gc_collected_objects(self, mock_gc_get_stats):
             }
         )
         expected_gc_collected_objects = [
-            _SystemMetricsResult({"generation": "0"}, 100),
-            _SystemMetricsResult({"generation": "1"}, 200),
-            _SystemMetricsResult({"generation": "2"}, 300),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 0, "generation": "0"}, 100
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 1, "generation": "1"}, 200
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 2, "generation": "2"}, 300
+            ),
         ]
         self._test_metrics(
             "cpython.gc.collected_objects",
@@ -1031,9 +1043,15 @@ def test_runtime_get_gc_uncollectable_objects(self, mock_gc_get_stats):
             }
         )
         expected_gc_uncollectable_objects = [
-            _SystemMetricsResult({"generation": "0"}, 1),
-            _SystemMetricsResult({"generation": "1"}, 2),
-            _SystemMetricsResult({"generation": "2"}, 3),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 0, "generation": "0"}, 1
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 1, "generation": "1"}, 2
+            ),
+            _SystemMetricsResult(
+                {"cpython.gc.generation": 2, "generation": "2"}, 3
+            ),
         ]
         self._test_metrics(
             "cpython.gc.uncollectable_objects",