Added the logger to warn users process.runtime.gc_count won't be coll…

…ected in case of PyPy

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

@@ -77,6 +77,7 @@
 
 import gc
 import os
+import logging
 import threading
 from platform import python_implementation
 from typing import Collection, Dict, Iterable, List, Optional
@@ -91,6 +92,9 @@
 from opentelemetry.metrics import CallbackOptions, Observation, get_meter
 from opentelemetry.sdk.util import get_dict_as_key
 
+logger = logging.getLogger(__name__)
+
+
 _DEFAULT_CONFIG = {
     "system.cpu.time": ["idle", "user", "system", "irq"],
     "system.cpu.utilization": ["idle", "user", "system", "irq"],
@@ -351,6 +355,9 @@ def _instrument(self, **kwargs):
             )
 
         if "process.runtime.gc_count" in self._config and self._python_implementation != "pypy":
+            logger.warning(
+                "The process.runtime.gc_count metric won't be collected because the interpreter is PyPy"
+            )
             self._meter.create_observable_counter(
                 name=f"process.runtime.{self._python_implementation}.gc_count",
                 callbacks=[self._get_runtime_gc_count],