fix(profiler): do not unload google.protobuf in module clean-up [backport #5747 to 1.10]

ddtrace/bootstrap/sitecustomize.py

@@ -121,7 +121,18 @@ def drop(module_name):
     # uses a copy of that module that is distinct from the copy that user code
     # gets when it does `import threading`. The same applies to every module
     # not in `KEEP_MODULES`.
-    KEEP_MODULES = frozenset(["atexit", "ddtrace", "asyncio", "concurrent", "typing", "logging", "attr"])
+    KEEP_MODULES = frozenset(
+        [
+            "atexit",
+            "ddtrace",
+            "asyncio",
+            "concurrent",
+            "typing",
+            "logging",
+            "attr",
+            "google.protobuf",  # the upb backend in >= 4.21 does not like being unloaded
+        ]
+    )
     if PY2:
         KEEP_MODULES_PY2 = frozenset(["encodings", "codecs"])
     for m in list(_ for _ in sys.modules if _ not in LOADED_MODULES):

releasenotes/notes/fix-profiler-segfault-in-protobuf-apps-032558829864cdfe.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    profiler: Fixed a bug that caused segmentation faults in applications that
+    use protobuf as a runtime dependency.

tests/profiling/test_main.py

@@ -124,3 +124,20 @@ def test_memalloc_no_init_error_on_fork():
     if not pid:
         exit(0)
     os.waitpid(pid, 0)
+
+
+@pytest.mark.subprocess(
+    ddtrace_run=True,
+    env=dict(
+        DD_PROFILING_ENABLED="1",
+        DD_UNLOAD_MODULES_FROM_SITECUSTOMIZE="1",
+    ),
+    out="OK\n",
+    err=None,
+)
+def test_profiler_start_up_with_module_clean_up_in_protobuf_app():
+    # This can cause segfaults if we do module clean up with later versions of
+    # protobuf. This is a regression test.
+    from google.protobuf import empty_pb2  # noqa
+
+    print("OK")