Enhance hook mechanism in dumper (#19073)

python/sglang/srt/debug_utils/dumper.py

@@ -1,3 +1,4 @@
+import functools
 import json
 import os
 import re
@@ -90,14 +91,14 @@ class _FrozenConfig(ABC):
 class _DumperConfig(_FrozenConfig):
     enable: bool = False
     filter: Optional[str] = None
-    dir: str = "/tmp"
+    dir: str = "/tmp/dumper"
     enable_output_file: bool = True
     enable_output_console: bool = True
     enable_value: bool = True
     enable_grad: bool = False
     enable_model_value: bool = True
     enable_model_grad: bool = True
-    partial_name: Optional[str] = None
+    exp_name: Optional[str] = None
     enable_http_server: bool = True
     cleanup_previous: bool = False
     collective_timeout: int = 60
@@ -176,7 +177,7 @@ class _Dumper:
             return
 
         # Users may want to `dump` only on some ranks, thus determine name here
-        self._ensure_partial_name()
+        self._ensure_exp_name()
 
         self._step += 1
         print(f"[Dumper] [{time.time()}] step={self._step}")
@@ -388,7 +389,7 @@ class _Dumper:
         save: bool,
         step: Optional[int] = None,
     ) -> None:
-        self._ensure_partial_name()
+        self._ensure_exp_name()
         self._dump_index += 1
 
         rank = _get_rank()
@@ -399,11 +400,7 @@ class _Dumper:
             **tags,
         )
         full_filename = _format_tags(full_kwargs) + ".pt"
-        path = (
+        path = Path(self._config.dir) / self._config.exp_name / full_filename
-            Path(self._config.dir)
-            / f"sglang_dump_{self._config.partial_name}"
-            / full_filename
-        )
 
         if self._config.enable_output_console:
             print(
@@ -468,11 +465,13 @@ class _Dumper:
                 _start_http_server(prefix="/dumper/", target=self, http_port=http_port)
                 print(f"[Dumper] HTTP server started on port {http_port}")
 
-    def _ensure_partial_name(self):
+    def _ensure_exp_name(self):
-        if self._config.partial_name is None:
+        if self._config.exp_name is None:
-            name = _get_partial_name(timeout_seconds=self._config.collective_timeout)
+            name = _get_default_exp_name(
-            self.configure(partial_name=name)
+                timeout_seconds=self._config.collective_timeout
-            print(f"[Dumper] Choose partial_name={name}")
+            )
+            self.configure(exp_name=name)
+            print(f"[Dumper] Choose exp_name={name}")
 
 
 # -------------------------------------- hook dumper ------------------------------------------
@@ -496,11 +495,16 @@ class _NonIntrusiveDumper:
             if ctx := self._detect_module_ctx(module_name, module):
                 self._register_ctx_hooks(module, ctx=ctx)
 
-            module.register_forward_hook(
+            is_root = module_name == ""
-                self._make_forward_hook(
+            pre_hook = self._make_forward_pre_hook(
-                    module_name=module_name,
+                module_name=module_name, is_root=is_root
-                    is_root=(module_name == ""),
+            )
-                )
+            hook = self._make_forward_hook(module_name=module_name, is_root=is_root)
+            _register_forward_hook_or_replace_fn(
+                module,
+                pre_hook=pre_hook,
+                hook=hook,
+                mode="replace_fn" if is_root else "hook",
             )
 
     @classmethod
@@ -525,11 +529,15 @@ class _NonIntrusiveDumper:
             )
         )
 
-    def _make_forward_hook(self, *, module_name: str, is_root: bool):
+    def _make_forward_pre_hook(self, *, module_name: str, is_root: bool):
-        def _hook(_module, input, output):
+        def _hook(_module, input):
             for i, item in enumerate(input):
                 self._dump_value(module_name, item, role=f"inputs.{i}", is_root=is_root)
 
+        return _hook
+
+    def _make_forward_hook(self, *, module_name: str, is_root: bool):
+        def _hook(_module, input, output):
             if output is not None:
                 self._dump_value(module_name, output, role="output", is_root=False)
 
@@ -566,6 +574,39 @@ class _NonIntrusiveDumper:
         return {}
 
 
+def _register_forward_hook_or_replace_fn(
+    module: "torch.nn.Module",
+    *,
+    pre_hook,
+    hook,
+    mode: str,
+) -> None:
+    """Attach pre/post forward hooks to *module*.
+
+    mode="hook"       — standard ``register_forward_pre_hook`` / ``register_forward_hook``
+                        (fires only via ``__call__``).
+    mode="replace_fn" — monkey-patch ``module.forward`` so hooks fire even when
+                        callers invoke ``.forward()`` directly (as sglang does for the
+                        root model).
+    """
+    if mode == "hook":
+        module.register_forward_pre_hook(pre_hook)
+        module.register_forward_hook(hook)
+    elif mode == "replace_fn":
+        original_forward = module.forward
+
+        @functools.wraps(original_forward)
+        def _wrapped(*args, **kwargs):
+            pre_hook(module, args)
+            output = original_forward(*args, **kwargs)
+            hook(module, args, output)
+            return output
+
+        module.forward = _wrapped
+    else:
+        raise ValueError(f"Unknown mode {mode!r}")
+
+
 # -------------------------------------- util fn ------------------------------------------
 
 
@@ -604,14 +645,14 @@ def _collective_with_timeout(fn, operation_name: str, timeout_seconds: int = 60)
         completed.set()
 
 
-def _get_partial_name(timeout_seconds: int = 60):
+def _get_default_exp_name(timeout_seconds: int = 60):
     rank = _get_rank()
-    object_list = [str(time.time()) if rank == 0 else None]
+    object_list = [f"dump_{time.time()}" if rank == 0 else None]
 
     if dist.is_initialized():
         _collective_with_timeout(
             lambda: dist.broadcast_object_list(object_list, device="cuda"),
-            operation_name="broadcast_object_list in _get_partial_name",
+            operation_name="broadcast_object_list in _get_default_exp_name",
             timeout_seconds=timeout_seconds,
         )
 
@@ -622,7 +663,7 @@ def _cleanup_old_dumps(base_dir: Path) -> None:
     import shutil
 
     if _get_rank() == 0:
-        for entry in base_dir.glob("sglang_dump_*"):
+        for entry in base_dir.glob("dump_*"):
             if entry.is_dir():
                 shutil.rmtree(entry)
                 print(f"[Dumper] Cleaned up {entry}")

test/registered/debug_utils/test_dump_comparator.py

@@ -108,7 +108,7 @@ class TestEndToEnd(CustomTestCase):
                 dumper.step()
                 dumper.dump("tensor_b", tensor * 2)
                 dumper.step()
-                dump_dirs.append(Path(d) / f"sglang_dump_{dumper._config.partial_name}")
+                dump_dirs.append(Path(d) / dumper._config.exp_name)
 
             args = Namespace(
                 baseline_path=str(dump_dirs[0]),

test/registered/debug_utils/test_dumper.py

@@ -440,7 +440,7 @@ def _make_test_dumper(tmp_path, **overrides) -> _Dumper:
     config = _DumperConfig(
         enable=True,
         dir=str(tmp_path),
-        partial_name="test",
+        exp_name="test",
         enable_http_server=False,
         **overrides,
     )
@@ -448,7 +448,7 @@ def _make_test_dumper(tmp_path, **overrides) -> _Dumper:
 
 
 def _get_filenames(tmpdir):
-    return {f.name for f in Path(tmpdir).glob("sglang_dump_*/*.pt")}
+    return {f.name for f in Path(tmpdir).glob("*/*.pt")}
 
 
 def _assert_files(filenames, *, exist=(), not_exist=()):
@@ -468,7 +468,7 @@ def _load_dump(path: Path) -> dict:
 def _find_dump_file(tmpdir, *, rank: int = 0, name: str) -> Path:
     matches = [
         f
-        for f in Path(tmpdir).glob("sglang_dump_*/*.pt")
+        for f in Path(tmpdir).glob("*/*.pt")
         if f"rank={rank}" in f.name and name in f.name
     ]
     assert (
@@ -770,7 +770,7 @@ class TestDumpModel:
 
 class TestCleanup:
     def test_cleanup_removes_old_dumps(self, tmp_path):
-        old_dir = tmp_path / "sglang_dump_old"
+        old_dir = tmp_path / "dump_old"
         old_dir.mkdir()
         (old_dir / "dummy.pt").touch()
 
@@ -781,7 +781,7 @@ class TestCleanup:
         _assert_files(_get_filenames(tmp_path), exist=["new_tensor"])
 
     def test_no_cleanup_by_default(self, tmp_path):
-        old_dir = tmp_path / "sglang_dump_old"
+        old_dir = tmp_path / "dump_old"
         old_dir.mkdir()
         (old_dir / "dummy.pt").touch()
 
@@ -1020,6 +1020,43 @@ class TestNonIntrusiveDumper(_NonIntrusiveTestBase):
         P = self._PREFIX
         assert torch.allclose(captured[f"{P}output"]["value"], output)
 
+    def test_inputs_dumped_before_forward(self, tmp_path):
+        """Inputs are captured *before* forward(); in-place mutation must not affect them."""
+
+        class Mutator(torch.nn.Module):
+            def forward(self, x):
+                x.fill_(999.0)
+                return x
+
+        class Inner(torch.nn.Module):
+            def __init__(self):
+                super().__init__()
+                self.mutator = Mutator()
+
+            def forward(self, x):
+                return self.mutator(x)
+
+        d = self._make_dumper(tmp_path)
+        model = self._wrap_as_outer(Inner)
+        d.register_non_intrusive_dumper(model)
+
+        x = torch.randn(2, 4)
+        original_x = x.clone()
+        with d.capture_output() as captured:
+            model(x)
+
+        P = self._PREFIX
+        dumped_input = captured[f"{P}model.mutator.inputs.0"]["value"]
+        assert torch.allclose(dumped_input, original_x), (
+            f"pre-hook should capture inputs before forward mutates them; "
+            f"got {dumped_input} but expected {original_x}"
+        )
+
+        dumped_output = captured[f"{P}model.mutator.output"]["value"]
+        assert (
+            dumped_output == 999.0
+        ).all(), "post-hook should capture outputs after forward"
+
     def test_hooks_all_module_levels(self, tmp_path):
         class Attention(torch.nn.Module):
             def __init__(self):