[python_safe_point_bias] Initial commit

Author: KowalskiThomas

scenarios/python_safe_point_bias_3.11/Dockerfile

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+ARG BASE_IMAGE="prof-python-3.11"
+FROM $BASE_IMAGE
+
+WORKDIR /usr/src/app
+
+COPY ./scenarios/python_safe_point_bias_3.11/ /usr/src/app
+
+RUN chmod 644 /usr/src/app/main.py
+RUN pip install --no-cache-dir -r requirements.txt
+
+ENV EXECUTION_TIME_SEC=20
+ENV DD_TRACE_DEBUG=false
+ENV DD_PROFILING_MEMORY_ENABLED=false
+
+CMD ddtrace-run python main.py

scenarios/python_safe_point_bias_3.11/README.md

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+# python_safe_point_bias_3.11
+
+Verifies that the Python profiler correctly attributes CPU time to `slow_method` rather than to `empty_method`, which is called from `slow_method` but does no work.
+
+## What the program does
+
+`slow_method` performs string concatenations and then calls `empty_method`, which is a no-op. The loop runs for the full `EXECUTION_TIME_SEC` duration.
+
+```python
+def empty_method() -> None:
+    pass
+
+def slow_method() -> None:
+    while time() < end_time:
+        x = "h" + "e" + "l" + "l" + "o" + ","
+        x += "w" + "o" + "r" + "l" + "d"
+        empty_method()
+```
+
+## Expected behavior
+
+- **cpu-time**: `slow_method` appears in ~100% of samples (inclusive), since all CPU work happens there.
+- **cpu-time**: `empty_method` appears in ~0% of samples; it is a no-op and should not be blamed for the CPU usage of its caller.
+
+A profiler with a blame-attribution bug would incorrectly show `empty_method` consuming significant CPU time.

scenarios/python_safe_point_bias_3.11/expected_profile.json

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+{
+  "test_name": "python_safe_point_bias",
+  "stacks": [
+    {
+      "profile-type": "cpu-time",
+      "stack-content": [
+        {
+          "regular_expression": ".*slow_method",
+          "percent": 100,
+          "error_margin": 5
+        },
+        {
+          "regular_expression": ".*empty_method",
+          "percent": 0,
+          "error_margin": 5
+        }
+      ]
+    }
+  ],
+  "scale_by_duration": true
+}

scenarios/python_safe_point_bias_3.11/main.py

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+import os
+from time import time
+
+
+def empty_method() -> None:
+    pass
+
+
+def slow_method() -> None:
+    execution_time_sec = float(os.getenv("EXECUTION_TIME_SEC", "10"))
+    end = time() + execution_time_sec
+    while time() < end:
+        x = "h" + "e" + "l" + "l" + "o" + ","
+        x += "w" + "o" + "r" + "l" + "d"
+        empty_method()
+
+
+if __name__ == "__main__":
+    slow_method()

scenarios/python_safe_point_bias_3.11/requirements.txt

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+ddtrace