[Rebase] Rebase to vllm 0.27.0 (#5976)

Signed-off-by: tzhouam <tzhouam@connect.ust.hk>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/engine/test_stage_engine_startup_cache_env.py

@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Regression tests for per-replica compile-cache isolation at spawn time.
+
+Replicas of the same stage compile the same model concurrently, and vLLM
+0.27's AOT compile (TritonBundler) races on the shared VLLM_CACHE_ROOT —
+a replica then dies with 'Cubin file saved by TritonBundler not found'
+(build 2954, Omni Perf Multi-Replica). Replica 0 must keep the default
+shared cache; additional replicas must spawn with an isolated cache dir,
+and the parent env must be restored afterwards.
+"""
+
+import os
+
+import pytest
+
+from vllm_omni.engine.stage_engine_startup import scoped_spawn_device_env
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+
+def test_replica_zero_keeps_shared_cache_root(monkeypatch):
+    monkeypatch.delenv("VLLM_CACHE_ROOT", raising=False)
+    with scoped_spawn_device_env(None, None, stage_id=1, replica_id=0):
+        assert "VLLM_CACHE_ROOT" not in os.environ
+    assert "VLLM_CACHE_ROOT" not in os.environ
+
+
+def test_additional_replica_gets_isolated_cache_root(monkeypatch):
+    monkeypatch.setenv("VLLM_CACHE_ROOT", "/tmp/base-cache")
+    with scoped_spawn_device_env(None, None, stage_id=2, replica_id=1):
+        assert os.environ["VLLM_CACHE_ROOT"] == os.path.join("/tmp/base-cache", "omni_stage2_replica1")
+    assert os.environ["VLLM_CACHE_ROOT"] == "/tmp/base-cache"
+
+
+def test_isolated_cache_root_defaults_without_env(monkeypatch):
+    monkeypatch.delenv("VLLM_CACHE_ROOT", raising=False)
+    with scoped_spawn_device_env(None, None, stage_id=0, replica_id=3):
+        assert os.environ["VLLM_CACHE_ROOT"].endswith("omni_stage0_replica3")
+        assert os.environ["VLLM_CACHE_ROOT"].startswith(os.path.expanduser("~/.cache/vllm"))
+    assert "VLLM_CACHE_ROOT" not in os.environ
+
+
+def test_missing_ids_leave_env_untouched(monkeypatch):
+    monkeypatch.delenv("VLLM_CACHE_ROOT", raising=False)
+    with scoped_spawn_device_env(None, None):
+        assert "VLLM_CACHE_ROOT" not in os.environ