Capture enqueue source via sys._getframe instead of inspect.stack

inspect.stack() walks the entire call stack and builds FrameInfo for
every frame just to read filename and lineno from frame 1. At realistic
stack depth that was ~500us of pure overhead per run_in_worker call;
sys._getframe(1) is ~75ns for the same information. Matches the
existing pattern in plain/plain/logs/logger.py.

Author: davegaeddert

plain-jobs/plain/jobs/jobs.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import datetime
-import inspect
+import sys
 import time
 from abc import ABCMeta, abstractmethod
 from contextlib import AbstractContextManager, nullcontext
@@ -96,16 +96,17 @@ def run_in_worker(
                 attributes={**metric_attributes, MESSAGING_OPERATION_NAME: "send"},
             ) as span:
                 try:
-                    # Try to automatically annotate the source of the job
-                    caller = inspect.stack()[1]
-                    source = f"{caller.filename}:{caller.lineno}"
+                    frame = sys._getframe(1)
+                    filename = frame.f_code.co_filename
+                    lineno = frame.f_lineno
+                    source = f"{filename}:{lineno}"
                     span.set_attributes(
                         {
-                            CODE_FILE_PATH: caller.filename,
-                            CODE_LINE_NUMBER: caller.lineno,
+                            CODE_FILE_PATH: filename,
+                            CODE_LINE_NUMBER: lineno,
                         }
                     )
-                except (IndexError, AttributeError):
+                except (ValueError, AttributeError):
                     source = ""
 
                 parameters = JobParameters.to_json(self._init_args, self._init_kwargs)