[Core] Add opt-in serialized HWR build admission

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

docs/design/feature/host_weight_runtime.md

@@ -313,6 +313,16 @@ One process per exact identity owns a build; other workers wait and then acquire
 leases for the published artifact. Publication is invisible until all payloads
 and metadata are validated, hashed, fsynced, and atomically renamed.
 
+By default, different identities may build concurrently. A domain configured
+with `CapacityPolicy(build_admission="serialized", max_store_bytes=...)` admits
+only one producer/publication operation at a time. Warm hits remain concurrent,
+and admission uses the existing coordination deadline. All workers must agree
+on the serialized domain's schema-2 capacity policy; use a new root when opting
+in, since in-place migration of an active domain is unsupported. This prevents
+competing producers from racing allocation checks but does not provide a
+filesystem-wide byte quota or automatic stale-data reclamation. See the
+[module capacity contract](../module/host_weight_runtime.md#validation-and-capacity).
+
 `coordination_timeout_seconds` bounds filesystem lock acquisition. It does not
 cancel synchronous validation, a producer that has already started, or atomic
 publication. A hung in-process producer therefore blocks its owning process and

docs/design/module/host_weight_runtime.md

@@ -311,9 +311,41 @@ point-in-time evidence only; kernel locks are not a persistent owner registry.
 Capacity policy covers all store-owned bytes, including ready, temporary, and
 quarantined data. The local writer preflights `max_artifact_bytes`,
 `max_store_bytes`, and `min_free_bytes`, and preallocates payloads where the
-filesystem supports it. `ENOSPC` remains a normal typed store failure because
-concurrent preflight is inherently racy. Automatic eviction and strict
-concurrent reservations are not implemented.
+filesystem supports it. `ENOSPC` remains a normal typed store failure.
+
+`CapacityPolicy.build_admission` defaults to `concurrent`, preserving parallel
+production for different identities and best-effort capacity preflight. An
+explicit `serialized` policy, which requires `max_store_bytes`, admits one
+cooperative build/publication operation per domain through
+`locks/domain-build.lock`. Production lock order becomes domain admission,
+per-key build, then artifact. Validated warm hits bypass admission; queued
+same-key callers still recheck and join a completed artifact. Admission waiting
+uses the caller's existing coordination deadline and returns a retryable build
+timeout without interrupting its owner.
+
+The kernel releases admission on process exit. An explicit same-key retry uses
+the existing stale-temp recovery; files from unrelated dead builds continue to
+count toward capacity. A synchronous producer that hangs still requires
+external process supervision. Admission release errors are logged without
+revising an already determined publication result.
+
+Concurrent domains retain their exact schema-1 capacity document. Serialized
+domains use a schema-2 capacity document with `build_admission=serialized`, so
+mixed policies and old readers fail initialization rather than bypass admission.
+Opt into serialization using a new root with an agreed policy; in-place policy
+migration while old workers may exist is unsupported. For example:
+
+```python
+from vllm_omni.host_weight_runtime import CapacityPolicy
+
+capacity = CapacityPolicy(max_store_bytes=192 * 1024**3, build_admission="serialized")
+```
+
+Serialization prevents cooperative producers from racing each other's
+allocation checks. It is not a filesystem quota: control metadata, finalization,
+and outside writers can still affect total usage. Automatic eviction and
+parallel byte reservations are not implemented. This policy trades parallel
+cold-build throughput for predictable producer admission.
 
 For tmpfs, artifact bytes are host-memory consumption and may consume swap;
 they must not be reported operationally as ordinary disk capacity. The store

tests/host_weight_runtime/test_build_admission.py

@@ -0,0 +1,305 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+"""CPU process and policy coverage for domain-wide producer admission."""
+
+from __future__ import annotations
+
+import errno
+import json
+import multiprocessing as mp
+import os
+import time
+from multiprocessing.connection import Connection
+from pathlib import Path
+from typing import Literal
+
+import pytest
+import torch
+
+from tests.host_weight_runtime.test_filesystem_store import FakeProducer, _identity, _make_store, _publish_test_artifact
+from vllm_omni.host_weight_runtime import (
+    BuildRequest,
+    CapacityPolicy,
+    FailureCode,
+    HostWeightError,
+    HostWeightRuntime,
+    HostWeightRuntimeConfig,
+    ProductionMetadata,
+    ResolutionOutcome,
+    RuntimeMode,
+    StoreResult,
+    StoreStatus,
+    TensorWriteSpec,
+    ValidationLevel,
+    WaitPolicy,
+    WeightArtifactIdentity,
+    WeightProductionSpec,
+)
+from vllm_omni.host_weight_runtime.filesystem.locks import FileLock, lock_is_active
+from vllm_omni.host_weight_runtime.protocols import ArtifactWriter
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+
+class AdmissionProducer:
+    def __init__(self, identity: WeightArtifactIdentity, control: Connection | None = None) -> None:
+        self._spec = FakeProducer(identity).spec
+        self.control = control
+
+    @property
+    def spec(self) -> WeightProductionSpec:
+        return self._spec
+
+    def produce(self, writer: ArtifactWriter) -> ProductionMetadata:
+        action = "produce"
+        if self.control is not None:
+            self.control.send("entered")
+            if not self.control.poll(60):
+                raise TimeoutError("test did not release producer")
+            action = self.control.recv()
+        spec = TensorWriteSpec("payload", (65536,), torch.bfloat16)
+        with writer.open_tensor_file("weights.safetensors", (spec,)) as output:
+            output.write_tensor("payload", torch.arange(65536, dtype=torch.float32).to(torch.bfloat16))
+            if action == "crash":
+                os._exit(27)
+        return ProductionMetadata("test-producer-v1", "test-restorer-v1")
+
+
+def _admission_process(root: Path, policy: CapacityPolicy, rank: int, control: Connection) -> None:
+    try:
+        store = _make_store(root, capacity=policy)
+        identity = _identity(tp_rank=rank)
+        original_lookup = store.lookup
+        first_lookup = True
+
+        def notify_lookup(
+            identity: WeightArtifactIdentity, *, validation: ValidationLevel, deadline: float | None = None
+        ) -> StoreResult:
+            nonlocal first_lookup
+            result = original_lookup(identity, validation=validation, deadline=deadline)
+            if first_lookup:
+                # Prove the caller observed a miss before the parent lets the
+                # active producer publish, independent of process scheduling.
+                control.send("looked_up")
+                first_lookup = False
+            return result
+
+        store.lookup = notify_lookup  # type: ignore[method-assign]
+        control.send("ready")
+        assert control.poll(60) and control.recv() == "start"
+        result = store.get_or_build(
+            BuildRequest(identity),
+            AdmissionProducer(identity, control),
+            validation=ValidationLevel.FULL_CHECKSUM,
+            deadline=time.monotonic() + 30,
+        )
+        if result.lease is not None:
+            result.lease.close()
+        control.send((result.status.value, result.failure.code.value if result.failure is not None else None))
+    finally:
+        control.close()
+
+
+@pytest.mark.parametrize("admission", ["concurrent", "serialized"])
+@pytest.mark.parametrize("same_key", [False, True])
+def test_cross_identity_admission_and_capacity(
+    tmp_path: Path, admission: Literal["concurrent", "serialized"], same_key: bool
+) -> None:
+    policy = CapacityPolicy(max_store_bytes=192 * 1024, build_admission=admission)
+    store = _make_store(tmp_path / "store", capacity=policy)
+    ctx = mp.get_context("spawn")
+    pairs = [ctx.Pipe() for _ in range(2)]
+    processes = [
+        ctx.Process(target=_admission_process, args=(store.root, policy, 0 if same_key else rank, pair[1]))
+        for rank, pair in enumerate(pairs)
+    ]
+    try:
+        for process, pair in zip(processes, pairs, strict=True):
+            process.start()
+            pair[1].close()
+        first, second = [pair[0] for pair in pairs]
+        for connection in (first, second):
+            assert connection.poll(60) and connection.recv() == "ready"
+        first.send("start")
+        assert first.poll(10) and first.recv() == "looked_up"
+        assert first.poll(10) and first.recv() == "entered"
+        second.send("start")
+        assert second.poll(10) and second.recv() == "looked_up"
+        if admission == "concurrent" and not same_key:
+            assert second.poll(10) and second.recv() == "entered"
+        else:
+            assert not second.poll(0.2), "a second producer entered while coordination should exclude it"
+        first.send("produce")
+        assert first.poll(30) and first.recv() == (StoreStatus.BUILT.value, None)
+        if same_key:
+            assert second.poll(30) and second.recv() == (StoreStatus.JOINED.value, None)
+        else:
+            if admission == "serialized":
+                assert second.poll(10) and second.recv() == "entered"
+            second.send("produce")
+            assert second.poll(30)
+            assert second.recv() == (StoreStatus.FAILED.value, FailureCode.STORE_LIMIT_EXCEEDED.value)
+        assert policy.max_store_bytes is not None
+        assert store.inspect_domain().store_bytes < policy.max_store_bytes
+        assert not list(store.tmp_dir.iterdir())
+        assert {path.name for path in store.artifacts_dir.iterdir()} == {_identity(tp_rank=0).key}
+        for process in processes:
+            process.join(10)
+            assert process.exitcode == 0
+    finally:
+        for process in processes:
+            if process.pid is not None:
+                if process.is_alive():
+                    process.kill()
+                process.join(5)
+                process.close()
+        for pair in pairs:
+            for connection in pair:
+                connection.close()
+
+
+def test_admission_timeout_preserves_owner_and_warm_hit_bypasses_lock(tmp_path: Path) -> None:
+    policy = CapacityPolicy(max_store_bytes=512 * 1024, build_admission="serialized")
+    store = _make_store(tmp_path / "store", capacity=policy)
+    identity, _ = _publish_test_artifact(store)
+    other = _identity(tp_rank=1)
+    lock_path = store.locks_dir / "domain-build.lock"
+    with FileLock(lock_path, exclusive=True, deadline=None):
+        hit = store.get_or_build(
+            BuildRequest(identity),
+            FakeProducer(identity),
+            validation=ValidationLevel.FULL_CHECKSUM,
+            deadline=time.monotonic() + 0.02,
+        )
+        assert hit.status is StoreStatus.HIT and hit.lease is not None
+        hit.lease.close()
+        timeout = store.get_or_build(
+            BuildRequest(other),
+            FakeProducer(other),
+            validation=ValidationLevel.FULL_CHECKSUM,
+            deadline=time.monotonic() + 0.02,
+        )
+        assert timeout.status is StoreStatus.TIMEOUT
+        assert timeout.failure is not None and timeout.failure.code is FailureCode.ACTIVE_BUILD_TIMEOUT
+        assert timeout.failure.retryable
+        assert lock_is_active(lock_path)
+    _publish_test_artifact(store, other)
+
+
+def test_producer_failure_releases_admission(tmp_path: Path) -> None:
+    store = _make_store(
+        tmp_path / "store", capacity=CapacityPolicy(max_store_bytes=16384, build_admission="serialized")
+    )
+    identity = _identity()
+    failed = store.get_or_build(
+        BuildRequest(identity),
+        FakeProducer(identity, write_mode="incomplete"),
+        validation=ValidationLevel.FULL_CHECKSUM,
+        deadline=time.monotonic() + 5,
+    )
+    assert failed.status is StoreStatus.FAILED
+    assert not lock_is_active(store.locks_dir / "domain-build.lock")
+    _publish_test_artifact(store, identity)
+
+
+@pytest.mark.parametrize(
+    ("mode", "expected"),
+    [(RuntimeMode.PREFERRED, ResolutionOutcome.CANONICAL_FALLBACK), (RuntimeMode.REQUIRED, ResolutionOutcome.FAILED)],
+)
+def test_admission_timeout_obeys_runtime_mode(tmp_path: Path, mode: RuntimeMode, expected: ResolutionOutcome) -> None:
+    policy = CapacityPolicy(max_store_bytes=16384, build_admission="serialized")
+    store = _make_store(tmp_path / "store", capacity=policy)
+    runtime = HostWeightRuntime.from_config(
+        HostWeightRuntimeConfig(mode=mode, domain=store.domain_policy, capacity=policy, wait=WaitPolicy(0.01))
+    )
+    identity = _identity()
+    with FileLock(store.locks_dir / "domain-build.lock", exclusive=True, deadline=None):
+        resolution = runtime.resolve(identity, producer=FakeProducer(identity))
+    assert resolution.report.outcome is expected
+    failure = resolution.report.attempts[-1].failure
+    assert failure is not None and failure.code is FailureCode.ACTIVE_BUILD_TIMEOUT
+
+
+def test_crashed_producer_releases_admission_and_same_key_retry_recovers(tmp_path: Path) -> None:
+    policy = CapacityPolicy(max_store_bytes=192 * 1024, build_admission="serialized")
+    store = _make_store(tmp_path / "store", capacity=policy)
+    ctx = mp.get_context("spawn")
+    parent, child = ctx.Pipe()
+    process = ctx.Process(target=_admission_process, args=(store.root, policy, 0, child))
+    process.start()
+    child.close()
+    try:
+        assert parent.poll(60) and parent.recv() == "ready"
+        parent.send("start")
+        assert parent.poll(10) and parent.recv() == "looked_up"
+        assert parent.poll(10) and parent.recv() == "entered"
+        parent.send("crash")
+        process.join(10)
+        assert process.exitcode == 27
+    finally:
+        if process.is_alive():
+            process.kill()
+        process.join(5)
+        process.close()
+        parent.close()
+    assert not lock_is_active(store.locks_dir / "domain-build.lock")
+    assert list(store.tmp_dir.iterdir())
+    identity = _identity(tp_rank=0)
+    recovered = store.get_or_build(
+        BuildRequest(identity),
+        AdmissionProducer(identity),
+        validation=ValidationLevel.FULL_CHECKSUM,
+        deadline=time.monotonic() + 10,
+    )
+    assert recovered.status is StoreStatus.BUILT and recovered.lease is not None
+    assert torch.equal(recovered.lease.tensors["payload"], torch.arange(65536, dtype=torch.float32).to(torch.bfloat16))
+    recovered.lease.close()
+    assert not list(store.tmp_dir.iterdir())
+
+
+def test_admission_release_error_preserves_publication(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    store = _make_store(
+        tmp_path / "store", capacity=CapacityPolicy(max_store_bytes=16384, build_admission="serialized")
+    )
+    original_close = FileLock.close
+
+    def fail_admission_close(lock: FileLock) -> None:
+        original_close(lock)
+        if lock.path.name == "domain-build.lock":
+            raise OSError(errno.EIO, "injected admission release failure")
+
+    monkeypatch.setattr(FileLock, "close", fail_admission_close)
+    _publish_test_artifact(store)
+    assert not lock_is_active(store.locks_dir / "domain-build.lock")
+
+
+def test_admission_policy_is_authoritative_and_legacy_document_is_unchanged(tmp_path: Path) -> None:
+    concurrent = CapacityPolicy(max_store_bytes=16384)
+    serialized = CapacityPolicy(max_store_bytes=16384, build_admission="serialized")
+    legacy = _make_store(tmp_path / "legacy", capacity=concurrent)
+    path = legacy.root / "domain-policy.json"
+    original = path.read_bytes()
+    assert json.loads(original) == {
+        "schema_version": 1,
+        "policy_version": 1,
+        "max_artifact_bytes": None,
+        "max_store_bytes": 16384,
+        "min_free_bytes": 0,
+        "eviction": "none",
+    }
+    with pytest.raises(HostWeightError, match="incompatible schema"):
+        _make_store(legacy.root, capacity=serialized)
+    assert path.read_bytes() == original
+    strict = _make_store(tmp_path / "serialized", capacity=serialized)
+    document = json.loads((strict.root / "domain-policy.json").read_bytes())
+    assert document["schema_version"] == 2 and document["build_admission"] == "serialized"
+    assert _make_store(strict.root, capacity=serialized).domain_uuid == strict.domain_uuid
+    with pytest.raises(HostWeightError, match="incompatible schema"):
+        _make_store(strict.root, capacity=concurrent)
+
+
+def test_admission_policy_validation() -> None:
+    with pytest.raises(ValueError, match="requires max_store_bytes"):
+        CapacityPolicy(build_admission="serialized")
+    with pytest.raises(ValueError, match="must be concurrent or serialized"):
+        CapacityPolicy(build_admission="unknown")  # type: ignore[arg-type]

vllm_omni/host_weight_runtime/config.py

@@ -8,6 +8,7 @@ import math
 from dataclasses import dataclass, field
 from enum import Enum
 from pathlib import Path
+from typing import Literal
 
 
 class RuntimeMode(str, Enum):
@@ -66,6 +67,7 @@ class CapacityPolicy:
     max_store_bytes: int | None = None
     min_free_bytes: int = 0
     eviction: str = "none"
+    build_admission: Literal["concurrent", "serialized"] = "concurrent"
 
     def __post_init__(self) -> None:
         for name, value in (
@@ -78,6 +80,10 @@ class CapacityPolicy:
             raise ValueError("min_free_bytes must not be negative")
         if not isinstance(self.eviction, str) or self.eviction != "none":
             raise ValueError("automatic host weight eviction is not implemented")
+        if self.build_admission not in ("concurrent", "serialized"):
+            raise ValueError("build_admission must be concurrent or serialized")
+        if self.build_admission == "serialized" and self.max_store_bytes is None:
+            raise ValueError("serialized build admission requires max_store_bytes")
 
 
 @dataclass(frozen=True)

vllm_omni/host_weight_runtime/filesystem/store.py

@@ -627,7 +627,7 @@ class FilesystemHostWeightStore:
                 self.policy_version = 1
 
     def _capacity_document(self, *, policy_version: int) -> dict[str, object]:
-        return {
+        document: dict[str, object] = {
             "schema_version": 1,
             "policy_version": policy_version,
             "max_artifact_bytes": self.capacity_policy.max_artifact_bytes,
@@ -635,6 +635,9 @@ class FilesystemHostWeightStore:
             "min_free_bytes": self.capacity_policy.min_free_bytes,
             "eviction": self.capacity_policy.eviction,
         }
+        if self.capacity_policy.build_admission == "serialized":
+            document.update(schema_version=2, build_admission="serialized")
+        return document
 
     def _build_lock_path(self, key: str) -> Path:
         return self.locks_dir / f"{key}.build.lock"
@@ -1013,6 +1016,40 @@ class FilesystemHostWeightStore:
         if initial.status in {StoreStatus.TIMEOUT, StoreStatus.FAILED}:
             return initial
 
+        if self.capacity_policy.build_admission == "concurrent":
+            return self._build_after_miss(identity, producer, validation=validation, deadline=deadline)
+        try:
+            admission = FileLock(self.locks_dir / "domain-build.lock", exclusive=True, deadline=deadline)
+        except FileLockTimeoutError as exc:
+            return StoreResult(
+                StoreStatus.TIMEOUT,
+                failure=_failure(
+                    ResolutionStage.PRODUCTION, FailureCode.ACTIVE_BUILD_TIMEOUT, str(exc), retryable=True
+                ),
+            )
+        except OSError as exc:
+            return StoreResult(
+                StoreStatus.FAILED,
+                failure=_failure(ResolutionStage.DOMAIN, FailureCode.DOMAIN_UNAVAILABLE, str(exc), retryable=True),
+            )
+        try:
+            return self._build_after_miss(identity, producer, validation=validation, deadline=deadline)
+        finally:
+            try:
+                admission.close()
+            except OSError:
+                # Releasing coordination must not revise the completed build's
+                # publication outcome or replace its primary failure.
+                logger.warning("Failed to release domain build admission under %s", self.root, exc_info=True)
+
+    def _build_after_miss(
+        self,
+        identity: WeightArtifactIdentity,
+        producer: WeightProducer,
+        *,
+        validation: ValidationLevel,
+        deadline: float,
+    ) -> StoreResult:
         try:
             build_lock = FileLock(self._build_lock_path(identity.key), exclusive=True, deadline=deadline)
         except FileLockTimeoutError as exc: