[Bugfix] Make the async-output wait bound configurable and default it higher (#6255)

Signed-off-by: ivanusto <ivanusto@gmail.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/test_async_output_timeout.py

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Unit tests for the async-output wait bound (_async_output_timeout)."""
+
+import logging
+
+import pytest
+
+from vllm_omni.diffusion.diffusion_engine import (
+    _ASYNC_OUTPUT_TIMEOUT_DEFAULT,
+    _ASYNC_OUTPUT_TIMEOUT_ENV,
+    _async_output_timeout,
+)
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+
+class TestAsyncOutputTimeoutIsConfigurable:
+    def test_default_is_generous(self, monkeypatch):
+        """The bound covers a copy queued behind a full denoise step, so the
+        default must not be tight enough to abort a slow but healthy render.
+        """
+        monkeypatch.delenv(_ASYNC_OUTPUT_TIMEOUT_ENV, raising=False)
+        assert _async_output_timeout() == _ASYNC_OUTPUT_TIMEOUT_DEFAULT == 600.0
+
+    def test_env_var_overrides_the_default(self, monkeypatch):
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, "1800")
+        assert _async_output_timeout() == 1800.0
+
+    def test_env_var_accepts_a_float(self, monkeypatch):
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, "45.5")
+        assert _async_output_timeout() == 45.5
+
+    def test_value_is_not_frozen_at_import(self, monkeypatch):
+        """Resolved per call rather than captured in a module constant, so the
+        value never goes stale relative to os.environ and no module reload is
+        needed to exercise it.
+        """
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, "60")
+        assert _async_output_timeout() == 60.0
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, "120")
+        assert _async_output_timeout() == 120.0
+
+
+class TestAsyncOutputTimeoutRejectsBadValues:
+    """This runs on the request path, so a typo in the environment must degrade
+    to the default rather than fail the generation.
+    """
+
+    @pytest.mark.parametrize("value", ["", "abc", "30s", "None"])
+    def test_non_numeric_falls_back_to_the_default(self, monkeypatch, caplog, value):
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, value)
+        with caplog.at_level(logging.WARNING):
+            assert _async_output_timeout() == _ASYNC_OUTPUT_TIMEOUT_DEFAULT
+
+    @pytest.mark.parametrize("value", ["0", "-1", "-0.5"])
+    def test_non_positive_falls_back_to_the_default(self, monkeypatch, caplog, value):
+        monkeypatch.setenv(_ASYNC_OUTPUT_TIMEOUT_ENV, value)
+        with caplog.at_level(logging.WARNING):
+            assert _async_output_timeout() == _ASYNC_OUTPUT_TIMEOUT_DEFAULT