perf(serverless): probe CPU info only for debugger

runpod/serverless/utils/rp_debugger.py

@@ -6,24 +6,43 @@
 
 import datetime
 from datetime import timezone
+import functools
 import platform
 import time
 
-import cpuinfo
-
 # ---------------------------------------------------------------------------- #
 #                                  System Info                                 #
 # ---------------------------------------------------------------------------- #
 OS_INFO = f"{platform.system()} {platform.release()}"
 
-try:
-    PROCESSOR = cpuinfo.get_cpu_info()["brand_raw"]
-except KeyError:
-    PROCESSOR = "Unable to get processor info."
-
 PYTHON_VERSION = platform.python_version()
 
 
+@functools.lru_cache(maxsize=1)
+def _get_processor() -> str:
+    """
+    Return the CPU brand string, probed on first use.
+
+    py-cpuinfo is slow on x86: it measures clock speed in a child process
+    around a fixed sleep(1). The worker imports this module on every start,
+    so probing here instead of at import keeps that second off cold starts
+    when the debugger is not enabled.
+    """
+    import cpuinfo  # pylint: disable=import-outside-toplevel
+
+    try:
+        return cpuinfo.get_cpu_info()["brand_raw"]
+    except KeyError:
+        return "Unable to get processor info."
+
+
+def __getattr__(name: str):
+    """Resolve PROCESSOR lazily for callers that read the module attribute."""
+    if name == "PROCESSOR":
+        return _get_processor()
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
 class Checkpoints:
     """
     A singleton class to store checkpoint times.
@@ -192,7 +211,7 @@ def get_debugger_output():
 
     system_info = {
         "os": OS_INFO,
-        "processor": PROCESSOR,
+        "processor": _get_processor(),
         "python_version": PYTHON_VERSION,
         "runpod": runpod.__version__,
     }

tests/test_serverless/test_utils/test_debugger.py

@@ -3,6 +3,8 @@
 """
 
 import importlib
+import subprocess
+import sys
 import time
 import unittest
 from unittest.mock import patch
@@ -23,18 +25,82 @@
     def setUp(self):
         self.checkpoints = Checkpoints()
         self.checkpoints.clear()
+        rp_debugger._get_processor.cache_clear()
 
-    @patch("runpod.serverless.utils.rp_debugger.cpuinfo.get_cpu_info")
+    def tearDown(self):
+        rp_debugger._get_processor.cache_clear()
+
+    @patch("cpuinfo.get_cpu_info")
+    def test_import_does_not_probe_cpu(self, mock_get_cpu_info):
+        """
+        Importing the module must not run py-cpuinfo; on x86 it sleeps 1s.
+        """
+        importlib.reload(rp_debugger)
+
+        mock_get_cpu_info.assert_not_called()
+
+    def test_import_does_not_load_cpuinfo(self):
+        """
+        Importing the module must not import py-cpuinfo, which spawns a subprocess at import.
+        """
+        result = subprocess.run(
+            [
+                sys.executable,
+                "-c",
+                "import sys; import runpod.serverless.utils.rp_debugger; "
+                "print('cpuinfo' in sys.modules)",
+            ],
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+
+        self.assertEqual(result.stdout.strip(), "False")
+
+    @patch("cpuinfo.get_cpu_info")
+    def test_debugger_output_reports_processor(self, mock_get_cpu_info):
+        """
+        The processor is looked up when debugger output is built.
+        """
+        mock_get_cpu_info.return_value = {"brand_raw": "Test CPU"}
+
+        output = get_debugger_output()
+
+        self.assertEqual(output["system_info"]["processor"], "Test CPU")
+
+    @patch("cpuinfo.get_cpu_info")
+    def test_processor_lookup_is_cached(self, mock_get_cpu_info):
+        """
+        The processor is probed once per process, not once per job.
+        """
+        mock_get_cpu_info.return_value = {"brand_raw": "Test CPU"}
+
+        get_debugger_output()
+        get_debugger_output()
+
+        mock_get_cpu_info.assert_called_once()
+
+    @patch("cpuinfo.get_cpu_info")
     def test_key_error(self, mock_get_cpu_info):
         """
-        Test that a KeyError is raised when an invalid key is used.
+        A missing brand string falls back to a placeholder.
         """
         mock_get_cpu_info.side_effect = KeyError("Test Error")
 
-        importlib.reload(rp_debugger)
+        output = get_debugger_output()
+
+        self.assertEqual(
+            output["system_info"]["processor"], "Unable to get processor info."
+        )
+
+    @patch("cpuinfo.get_cpu_info")
+    def test_processor_attribute_is_lazy(self, mock_get_cpu_info):
+        """
+        The PROCESSOR module attribute still resolves for existing callers.
+        """
+        mock_get_cpu_info.return_value = {"brand_raw": "Test CPU"}
 
-        assert mock_get_cpu_info.called
-        self.assertEqual(rp_debugger.PROCESSOR, "Unable to get processor info.")
+        self.assertEqual(rp_debugger.PROCESSOR, "Test CPU")
 
     def test_checkpoints(self):
         """