[Core] add an option to log every function call to for debugging hang/crash in distributed inference (#4079)

Co-authored-by: Simon Mo <simon.mo@hey.com>

tests/test_logger.py

@@ -0,0 +1,27 @@
+import os
+import sys
+import tempfile
+
+from vllm.logger import enable_trace_function_call
+
+
+def f1(x):
+    return f2(x)
+
+
+def f2(x):
+    return x
+
+
+def test_trace_function_call():
+    fd, path = tempfile.mkstemp()
+    cur_dir = os.path.dirname(__file__)
+    enable_trace_function_call(path, cur_dir)
+    f1(1)
+    with open(path, 'r') as f:
+        content = f.read()
+
+    assert "f1" in content
+    assert "f2" in content
+    sys.settrace(None)
+    os.remove(path)