[Feature] OTEL tracing during loading (#31162)

tests/tracing/test_loading_tracing.py

@@ -0,0 +1,87 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import asyncio
+
+import pytest
+from opentelemetry.sdk.environment_variables import OTEL_EXPORTER_OTLP_TRACES_INSECURE
+
+from tests.tracing.conftest import FAKE_TRACE_SERVER_ADDRESS, FakeTraceService
+from vllm.tracing import init_tracer, instrument, is_otel_available
+
+# Skip everything if OTel is missing
+pytestmark = pytest.mark.skipif(not is_otel_available(), reason="OTel required")
+
+
+class TestCoreInstrumentation:
+    """Focuses on the @instrument decorator's ability to capture execution data."""
+
+    @pytest.fixture(autouse=True)
+    def setup_tracing(self, monkeypatch):
+        monkeypatch.setenv(OTEL_EXPORTER_OTLP_TRACES_INSECURE, "true")
+        init_tracer("test.core", FAKE_TRACE_SERVER_ADDRESS)
+
+    def test_decorator_captures_sync_and_async(self, trace_service: FakeTraceService):
+        """Verify basic span creation for both sync and async functions."""
+
+        @instrument(span_name="sync_task")
+        def sync_task():
+            return True
+
+        @instrument(span_name="async_task")
+        async def async_task():
+            return True
+
+        sync_task()
+        asyncio.run(async_task())
+
+        assert trace_service.wait_for_spans(count=2)
+        span_names = [s["name"] for s in trace_service.get_all_spans()]
+        assert "sync_task" in span_names
+        assert "async_task" in span_names
+
+    def test_nested_spans_hierarchy(self, trace_service: FakeTraceService):
+        """Verify that nested calls create a parent-child relationship."""
+
+        @instrument(span_name="child")
+        def child():
+            pass
+
+        @instrument(span_name="parent")
+        def parent():
+            child()
+
+        parent()
+
+        assert trace_service.wait_for_spans(count=2)
+        spans = trace_service.get_all_spans()
+        parent_span = next(s for s in spans if s["name"] == "parent")
+        child_span = next(s for s in spans if s["name"] == "child")
+
+        assert child_span["parent_span_id"] == parent_span["span_id"]
+
+
+class TestInterProcessPropagation:
+    """Test the propagation of trace context between processes."""
+
+    def test_pickup_external_context(self, monkeypatch, trace_service):
+        """Test that vLLM attaches to an existing trace ID if in environment."""
+        monkeypatch.setenv(OTEL_EXPORTER_OTLP_TRACES_INSECURE, "true")
+
+        # Manually simulate an external parent trace ID
+        fake_trace_id = "4bf92f3577b34da6a3ce929d0e0e4736"
+        fake_parent_id = "00f067aa0ba902b7"
+        monkeypatch.setenv("traceparent", f"00-{fake_trace_id}-{fake_parent_id}-01")
+
+        init_tracer("test.external", FAKE_TRACE_SERVER_ADDRESS)
+
+        @instrument(span_name="follower")
+        def follower_func():
+            pass
+
+        follower_func()
+
+        assert trace_service.wait_for_spans(count=1)
+        span = trace_service.get_all_spans()[0]
+
+        assert span["trace_id"] == fake_trace_id
+        assert span["parent_span_id"] == fake_parent_id