opentelemetry-instrumentation-system-metrics: fix running on Google Cloud Run

psutil fails reading context switches fails on Google Cloud Run, so
before setting up the observable counter trying to read the values check
we are actually being able to do so.

Author: xrmx

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

@@ -395,7 +395,10 @@ def _instrument(self, **kwargs: Any):
                 self._meter, callbacks=[self._get_cpu_utilization]
             )
 
-        if "process.context_switches" in self._config:
+        if (
+            "process.context_switches" in self._config
+            and self._can_read_context_switches()
+        ):
             self._meter.create_observable_counter(
                 name="process.context_switches",
                 callbacks=[self._get_context_switches],
@@ -482,7 +485,10 @@ def _instrument(self, **kwargs: Any):
                 unit="1",
             )
 
-        if "process.runtime.context_switches" in self._config:
+        if (
+            "process.runtime.context_switches" in self._config
+            and self._can_read_context_switches()
+        ):
             self._meter.create_observable_counter(
                 name=f"process.runtime.{self._python_implementation}.context_switches",
                 callbacks=[self._get_runtime_context_switches],
@@ -493,6 +499,14 @@ def _instrument(self, **kwargs: Any):
     def _uninstrument(self, **kwargs: Any):
         pass
 
+    def _can_read_context_switches(self) -> bool:
+        """On Google Cloud Run psutil is not able to read context switches, catch it before creating the observable instrument"""
+        try:
+            self._proc.num_ctx_switches()
+            return True
+        except NotImplementedError:
+            return False
+
     def _get_open_file_descriptors(
         self, options: CallbackOptions
     ) -> Iterable[Observation]:

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

@@ -855,6 +855,24 @@ def test_context_switches(self, mock_process_num_ctx_switches):
         ]
         self._test_metrics("process.context_switches", expected)
 
+    @mock.patch("psutil.Process.num_ctx_switches")
+    def test_context_switches_not_implemented_error(
+        self, mock_process_num_ctx_switches
+    ):
+        mock_process_num_ctx_switches.side_effect = NotImplementedError
+
+        reader = InMemoryMetricReader()
+        meter_provider = MeterProvider(metric_readers=[reader])
+        system_metrics = SystemMetricsInstrumentor()
+        system_metrics.instrument(meter_provider=meter_provider)
+
+        seen_metrics = set()
+        for resource_metrics in reader.get_metrics_data().resource_metrics:
+            for scope_metrics in resource_metrics.scope_metrics:
+                for metric in scope_metrics.metrics:
+                    seen_metrics.add(metric.name)
+        self.assertNotIn("process.context_switches", seen_metrics)
+
     @mock.patch("psutil.Process.num_threads")
     def test_thread_count(self, mock_process_thread_num):
         mock_process_thread_num.configure_mock(**{"return_value": 42})