add gc_count metrics with correct collection unit .

fixes #3549

Author: david-gang

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3610](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3610))
 - `opentelemetry-instrumentation-kafka-python` Utilize instruments-any functionality.
   ([#3610](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3610))
+- `opentelemetry-instrumentation-system-metrics`: Add `cpython.gc.collections` metrics with collection unit is specified in semconv ([3617](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3617))
 
 ## Version 1.35.0/0.56b0 (2025-07-11)
 

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

@@ -44,6 +44,7 @@
         "process.runtime.memory": ["rss", "vms"],
         "process.runtime.cpu.time": ["user", "system"],
         "process.runtime.gc_count": None,
+        "cpython.gc.collections": None,
         "process.runtime.thread_count": None,
         "process.runtime.cpu.utilization": None,
         "process.runtime.context_switches": ["involuntary", "voluntary"],
@@ -136,6 +137,7 @@
     "process.runtime.memory": ["rss", "vms"],
     "process.runtime.cpu.time": ["user", "system"],
     "process.runtime.gc_count": None,
+    "cpython.gc.collections": None,
     "process.runtime.thread_count": None,
     "process.runtime.cpu.utilization": None,
     "process.runtime.context_switches": ["involuntary", "voluntary"],
@@ -196,6 +198,7 @@ def __init__(
         self._runtime_memory_labels = self._labels.copy()
         self._runtime_cpu_time_labels = self._labels.copy()
         self._runtime_gc_count_labels = self._labels.copy()
+        self._runtime_gc_collections_labels = self._labels.copy()
         self._runtime_thread_count_labels = self._labels.copy()
         self._runtime_cpu_utilization_labels = self._labels.copy()
         self._runtime_context_switches_labels = self._labels.copy()
@@ -470,6 +473,19 @@ def _instrument(self, **kwargs: Any):
                     unit="By",
                 )
 
+        if "cpython.gc.collections" in self._config:
+            if self._python_implementation == "pypy":
+                _logger.warning(
+                    "The cpython.gc.collections metric won't be collected because the interpreter is PyPy"
+                )
+            else:
+                self._meter.create_observable_counter(
+                    name="cpython.gc.collections",
+                    callbacks=[self._get_runtime_gc_collections],
+                    description="The number of times a generation was collected since interpreter start.",
+                    unit="{collection}",
+                )
+
         if "process.runtime.thread_count" in self._config:
             self._meter.create_observable_up_down_counter(
                 name=f"process.runtime.{self._python_implementation}.thread_count",
@@ -885,6 +901,16 @@ def _get_runtime_gc_count(
             self._runtime_gc_count_labels["count"] = str(index)
             yield Observation(count, self._runtime_gc_count_labels.copy())
 
+    def _get_runtime_gc_collections(
+        self, options: CallbackOptions
+    ) -> Iterable[Observation]:
+        """Observer callback for garbage collection"""
+        for index, count in enumerate(gc.get_count()):
+            self._runtime_gc_collections_labels["generation"] = str(index)
+            yield Observation(
+                count, self._runtime_gc_collections_labels.copy()
+            )
+
     def _get_runtime_thread_count(
         self, options: CallbackOptions
     ) -> Iterable[Observation]:

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

@@ -136,6 +136,9 @@ def test_system_metrics_instrument(self):
             observer_names.append(
                 f"process.runtime.{self.implementation}.gc_count",
             )
+            observer_names.append(
+                "cpython.gc.collections",
+            )
         if sys.platform != "darwin":
             observer_names.append("system.network.connections")
 
@@ -946,13 +949,30 @@ def test_runtime_cpu_time(self, mock_process_cpu_times):
     def test_runtime_get_count(self, mock_gc_get_count):
         mock_gc_get_count.configure_mock(**{"return_value": (1, 2, 3)})
 
-        expected = [
+        expected_gc_count = [
             _SystemMetricsResult({"count": "0"}, 1),
             _SystemMetricsResult({"count": "1"}, 2),
             _SystemMetricsResult({"count": "2"}, 3),
         ]
         self._test_metrics(
-            f"process.runtime.{self.implementation}.gc_count", expected
+            f"process.runtime.{self.implementation}.gc_count",
+            expected_gc_count,
+        )
+
+    @mock.patch("gc.get_count")
+    @skipIf(
+        python_implementation().lower() == "pypy", "not supported for pypy"
+    )
+    def test_runtime_get_gc_collections(self, mock_gc_get_count):
+        mock_gc_get_count.configure_mock(**{"return_value": (1, 2, 3)})
+        expected_gc_collections = [
+            _SystemMetricsResult({"generation": "0"}, 1),
+            _SystemMetricsResult({"generation": "1"}, 2),
+            _SystemMetricsResult({"generation": "2"}, 3),
+        ]
+        self._test_metrics(
+            "cpython.gc.collections",
+            expected_gc_collections,
         )
 
     @mock.patch("psutil.Process.num_ctx_switches")