[Feature] OTEL tracing during loading (#31162)

requirements/common.txt

@@ -52,4 +52,4 @@ anthropic >= 0.71.0
 model-hosting-container-standards >= 0.1.13, < 1.0.0
 mcp
 grpcio
-grpcio-reflection
+grpcio-reflection
\ No newline at end of file

setup.py

@@ -1049,6 +1049,13 @@ setup(
         "petit-kernel": ["petit-kernel"],
         # Optional deps for Helion kernel development
         "helion": ["helion"],
+        # Optional deps for OpenTelemetry tracing
+        "otel": [
+            "opentelemetry-sdk>=1.26.0",
+            "opentelemetry-api>=1.26.0",
+            "opentelemetry-exporter-otlp>=1.26.0",
+            "opentelemetry-semantic-conventions-ai>=0.4.1",
+        ],
     },
     cmdclass=cmdclass,
     package_data=package_data,

tests/tracing/conftest.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import threading
+from collections.abc import Callable, Generator, Iterable
+from concurrent import futures
+from typing import Any, Literal
+
+import grpc
+import pytest
+from opentelemetry.proto.collector.trace.v1.trace_service_pb2 import (
+    ExportTraceServiceRequest,
+    ExportTraceServiceResponse,
+)
+from opentelemetry.proto.collector.trace.v1.trace_service_pb2_grpc import (
+    TraceServiceServicer,
+    add_TraceServiceServicer_to_server,
+)
+from opentelemetry.proto.common.v1.common_pb2 import AnyValue, KeyValue
+
+FAKE_TRACE_SERVER_ADDRESS = "localhost:4317"
+
+FieldName = Literal[
+    "bool_value", "string_value", "int_value", "double_value", "array_value"
+]
+
+
+def decode_value(value: AnyValue):
+    """Decode an OpenTelemetry AnyValue protobuf message to a Python value."""
+    field_decoders: dict[FieldName, Callable] = {
+        "bool_value": (lambda v: v.bool_value),
+        "string_value": (lambda v: v.string_value),
+        "int_value": (lambda v: v.int_value),
+        "double_value": (lambda v: v.double_value),
+        "array_value": (
+            lambda v: [decode_value(item) for item in v.array_value.values]
+        ),
+    }
+    for field, decoder in field_decoders.items():
+        if value.HasField(field):
+            return decoder(value)
+    raise ValueError(f"Couldn't decode value: {value}")
+
+
+def decode_attributes(attributes: Iterable[KeyValue]) -> dict[str, Any]:
+    """Decode OpenTelemetry KeyValue attributes to a Python dictionary."""
+    return {kv.key: decode_value(kv.value) for kv in attributes}
+
+
+class FakeTraceService(TraceServiceServicer):
+    """A fake gRPC trace service for testing OpenTelemetry trace exports."""
+
+    def __init__(self):
+        self.requests: list[ExportTraceServiceRequest] = []
+        self.evt = threading.Event()
+        self._lock = threading.Lock()
+
+    def Export(self, request, context):
+        with self._lock:
+            self.requests.append(request)
+        self.evt.set()
+        return ExportTraceServiceResponse()
+
+    @property
+    def request(self) -> ExportTraceServiceRequest | None:
+        """Returns the first request received (for backward compatibility)."""
+        with self._lock:
+            return self.requests[0] if self.requests else None
+
+    def get_all_spans(self) -> list[dict]:
+        """Returns all spans from all received requests as decoded dicts."""
+        spans = []
+        with self._lock:
+            for request in self.requests:
+                for resource_span in request.resource_spans:
+                    for scope_span in resource_span.scope_spans:
+                        for span in scope_span.spans:
+                            spans.append(
+                                {
+                                    "name": span.name,
+                                    "attributes": decode_attributes(span.attributes),
+                                    "trace_id": span.trace_id.hex(),
+                                    "span_id": span.span_id.hex(),
+                                    "parent_span_id": span.parent_span_id.hex()
+                                    if span.parent_span_id
+                                    else None,
+                                    "start_time_unix_nano": span.start_time_unix_nano,
+                                    "end_time_unix_nano": span.end_time_unix_nano,
+                                }
+                            )
+        return spans
+
+    def wait_for_spans(self, count: int = 1, timeout: float = 10) -> bool:
+        """Wait until at least `count` spans have been received."""
+        import time
+
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            if len(self.get_all_spans()) >= count:
+                return True
+            time.sleep(0.1)
+        return False
+
+    def clear(self):
+        """Clear all received requests."""
+        with self._lock:
+            self.requests.clear()
+        self.evt.clear()
+
+
+@pytest.fixture
+def trace_service() -> Generator[FakeTraceService, None, None]:
+    """Fixture to set up a fake gRPC trace service."""
+    server = grpc.server(futures.ThreadPoolExecutor(max_workers=2))
+    service = FakeTraceService()
+    add_TraceServiceServicer_to_server(service, server)
+    server.add_insecure_port(FAKE_TRACE_SERVER_ADDRESS)
+    server.start()
+
+    yield service
+
+    server.stop(grace=None)
+
+
+@pytest.fixture
+def trace_server_address() -> str:
+    """Returns the address of the fake trace server."""
+    return FAKE_TRACE_SERVER_ADDRESS

tests/tracing/test_loading_tracing.py

+# 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

tests/v1/tracing/test_tracing.py

@@ -2,76 +2,19 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 # ruff: noqa
 # type: ignore
-import threading
-from collections.abc import Iterable
-from concurrent import futures
-from typing import Callable, Generator, Literal
-
-import grpc
 import pytest
-from opentelemetry.proto.collector.trace.v1.trace_service_pb2 import (
-    ExportTraceServiceResponse,
-)
-from opentelemetry.proto.collector.trace.v1.trace_service_pb2_grpc import (
-    TraceServiceServicer,
-    add_TraceServiceServicer_to_server,
-)
-from opentelemetry.proto.common.v1.common_pb2 import AnyValue, KeyValue
+import time
 from opentelemetry.sdk.environment_variables import OTEL_EXPORTER_OTLP_TRACES_INSECURE
 
 from vllm import LLM, SamplingParams
 from vllm.tracing import SpanAttributes
 
-FAKE_TRACE_SERVER_ADDRESS = "localhost:4317"
-
-FieldName = Literal[
-    "bool_value", "string_value", "int_value", "double_value", "array_value"
-]
-
-
-def decode_value(value: AnyValue):
-    field_decoders: dict[FieldName, Callable] = {
-        "bool_value": (lambda v: v.bool_value),
-        "string_value": (lambda v: v.string_value),
-        "int_value": (lambda v: v.int_value),
-        "double_value": (lambda v: v.double_value),
-        "array_value": (
-            lambda v: [decode_value(item) for item in v.array_value.values]
-        ),
-    }
-    for field, decoder in field_decoders.items():
-        if value.HasField(field):
-            return decoder(value)
-    raise ValueError(f"Couldn't decode value: {value}")
-
-
-def decode_attributes(attributes: Iterable[KeyValue]):
-    return {kv.key: decode_value(kv.value) for kv in attributes}
-
-
-class FakeTraceService(TraceServiceServicer):
-    def __init__(self):
-        self.request = None
-        self.evt = threading.Event()
-
-    def Export(self, request, context):
-        self.request = request
-        self.evt.set()
-        return ExportTraceServiceResponse()
-
-
-@pytest.fixture
-def trace_service() -> Generator[FakeTraceService, None, None]:
-    """Fixture to set up a fake gRPC trace service"""
-    server = grpc.server(futures.ThreadPoolExecutor(max_workers=1))
-    service = FakeTraceService()
-    add_TraceServiceServicer_to_server(service, server)
-    server.add_insecure_port(FAKE_TRACE_SERVER_ADDRESS)
-    server.start()
-
-    yield service
-
-    server.stop(None)
+# Import shared fixtures from the tracing conftest
+from tests.tracing.conftest import (  # noqa: F401
+    FAKE_TRACE_SERVER_ADDRESS,
+    FakeTraceService,
+    trace_service,
+)
 
 
 def test_traces(
@@ -97,29 +40,25 @@ def test_traces(
         outputs = llm.generate(prompts, sampling_params=sampling_params)
         print(f"test_traces outputs is : {outputs}")
 
-        timeout = 10
-        if not trace_service.evt.wait(timeout):
-            raise TimeoutError(
-                f"The fake trace service didn't receive a trace within "
-                f"the {timeout} seconds timeout"
-            )
-
-        request = trace_service.request
-        assert len(request.resource_spans) == 1, (
-            f"Expected 1 resource span, but got {len(request.resource_spans)}"
-        )
-        assert len(request.resource_spans[0].scope_spans) == 1, (
-            f"Expected 1 scope span, "
-            f"but got {len(request.resource_spans[0].scope_spans)}"
-        )
-        assert len(request.resource_spans[0].scope_spans[0].spans) == 1, (
-            f"Expected 1 span, "
-            f"but got {len(request.resource_spans[0].scope_spans[0].spans)}"
+        # Wait for the "llm_request" span to be exported.
+        # The BatchSpanProcessor batches spans and exports them periodically,
+        # so we need to wait specifically for the llm_request span to appear.
+        timeout = 15
+        deadline = time.time() + timeout
+        llm_request_spans = []
+        while time.time() < deadline:
+            all_spans = trace_service.get_all_spans()
+            llm_request_spans = [s for s in all_spans if s["name"] == "llm_request"]
+            if llm_request_spans:
+                break
+            time.sleep(0.5)
+
+        assert len(llm_request_spans) == 1, (
+            f"Expected exactly 1 'llm_request' span, but got {len(llm_request_spans)}. "
+            f"All span names: {[s['name'] for s in all_spans]}"
         )
 
-        attributes = decode_attributes(
-            request.resource_spans[0].scope_spans[0].spans[0].attributes
-        )
+        attributes = llm_request_spans[0]["attributes"]
         # assert attributes.get(SpanAttributes.GEN_AI_RESPONSE_MODEL) == model
         assert attributes.get(SpanAttributes.GEN_AI_REQUEST_ID) == outputs[0].request_id
         assert (

vllm/compilation/backends.py

@@ -33,6 +33,7 @@ from vllm.config.utils import Range, hash_factors
 from vllm.logger import init_logger
 from vllm.logging_utils import lazy
 from vllm.platforms import current_platform
+from vllm.tracing import instrument, instrument_manual
 from vllm.utils.import_utils import resolve_obj_by_qualname
 
 from .compiler_interface import (
@@ -234,6 +235,7 @@ class CompilerManager:
         )
         return compiled_graph
 
+    @instrument(span_name="Compile graph")
     def compile(
         self,
         graph: fx.GraphModule,
@@ -497,6 +499,7 @@ class PiecewiseCompileInterpreter(torch.fx.Interpreter):  # type: ignore[misc]
         # When True, it annoyingly dumps the torch.fx.Graph on errors.
         self.extra_traceback = False
 
+    @instrument(span_name="Inductor compilation")
     def run(self, *args: Any) -> Any:
         # maybe instead just assert inputs are fake?
         fake_args = [
@@ -922,6 +925,11 @@ class VllmBackend:
         )
         self.compilation_config.compilation_time += dynamo_time
 
+        # Record Dynamo time in tracing if available
+        start_time = int(torch_compile_start_time * 1e9)
+        attributes = {"dynamo.time_seconds": dynamo_time}
+        instrument_manual("Dynamo bytecode transform", start_time, None, attributes)
+
         # we control the compilation process, each instance can only be
         # called once
         assert not self._called, "VllmBackend can only be called once"

vllm/config/observability.py

@@ -122,9 +122,9 @@ class ObservabilityConfig:
     @classmethod
     def _validate_otlp_traces_endpoint(cls, value: str | None) -> str | None:
         if value is not None:
-            from vllm.tracing import is_otel_available, otel_import_error_traceback
+            from vllm.tracing import is_tracing_available, otel_import_error_traceback
 
-            if not is_otel_available():
+            if not is_tracing_available():
                 raise ValueError(
                     "OpenTelemetry is not available. Unable to configure "
                     "'otlp_traces_endpoint'. Ensure OpenTelemetry packages are "

vllm/entrypoints/openai/api_server.py

@@ -50,6 +50,7 @@ from vllm.logger import init_logger
 from vllm.reasoning import ReasoningParserManager
 from vllm.tasks import POOLING_TASKS, SupportedTask
 from vllm.tool_parsers import ToolParserManager
+from vllm.tracing import instrument
 from vllm.usage.usage_lib import UsageContext
 from vllm.utils.argparse_utils import FlexibleArgumentParser
 from vllm.utils.network_utils import is_valid_ipv6_address
@@ -377,6 +378,7 @@ def validate_api_server_args(args):
         )
 
 
+@instrument(span_name="API server setup")
 def setup_server(args):
     """Validate API server args, set up signal handler, create socket
     ready to serve."""

vllm/model_executor/model_loader/base_loader.py

@@ -14,6 +14,7 @@ from vllm.model_executor.model_loader.utils import (
     process_weights_after_loading,
 )
 from vllm.platforms import current_platform
+from vllm.tracing import instrument
 from vllm.utils.mem_utils import format_gib
 from vllm.utils.torch_utils import set_default_torch_dtype
 
@@ -37,6 +38,7 @@ class BaseModelLoader(ABC):
         inplace weights loading for an already-initialized model"""
         raise NotImplementedError
 
+    @instrument(span_name="Load model")
     def load_model(
         self, vllm_config: VllmConfig, model_config: ModelConfig, prefix: str = ""
     ) -> nn.Module:

vllm/model_executor/model_loader/default_loader.py

@@ -30,6 +30,7 @@ from vllm.model_executor.model_loader.weight_utils import (
     pt_weights_iterator,
     safetensors_weights_iterator,
 )
+from vllm.tracing import instrument
 from vllm.transformers_utils.repo_utils import list_filtered_repo_files
 
 logger = init_logger(__name__)
@@ -274,6 +275,7 @@ class DefaultModelLoader(BaseModelLoader):
             allow_patterns_overrides=None,
         )
 
+    @instrument(span_name="Load weights")
     def load_weights(self, model: nn.Module, model_config: ModelConfig) -> None:
         if model_config.quantization == "torchao":
             quant_config = get_quant_config(model_config, self.load_config)

vllm/model_executor/model_loader/utils.py

@@ -23,11 +23,13 @@ from vllm.model_executor.model_loader.reload import (
     set_torchao_reload_attrs,
 )
 from vllm.model_executor.models.interfaces import SupportsQuant
+from vllm.tracing import instrument
 from vllm.utils.platform_utils import is_pin_memory_available
 
 logger = init_logger(__name__)
 
 
+@instrument(span_name="Initialize model")
 def initialize_model(
     vllm_config: VllmConfig,
     *,

vllm/model_executor/model_loader/weight_utils.py

@@ -36,6 +36,7 @@ from vllm.model_executor.layers.quantization import (
     get_quantization_config,
 )
 from vllm.platforms import current_platform
+from vllm.tracing import instrument
 from vllm.utils.import_utils import PlaceholderModule
 
 try:
@@ -443,6 +444,7 @@ def download_gguf(
     return local_files[0]
 
 
+@instrument(span_name="Download weights - HF")
 def download_weights_from_hf(
     model_name_or_path: str,
     cache_dir: str | None,

vllm/model_executor/warmup/deep_gemm_warmup.py

@@ -19,6 +19,7 @@ from vllm.model_executor.layers.fused_moe.triton_deep_gemm_moe import (
 )
 from vllm.model_executor.layers.linear import LinearBase
 from vllm.model_executor.layers.quantization.fp8 import Fp8LinearMethod
+from vllm.tracing import instrument
 from vllm.utils.deep_gemm import (
     fp8_gemm_nt,
     get_mk_alignment_for_contiguous_layout,
@@ -358,6 +359,7 @@ def _count_warmup_iterations(model: torch.nn.Module, max_tokens: int) -> int:
     return total
 
 
+@instrument(span_name="DeepGemm warmup")
 def deep_gemm_warmup(model: torch.nn.Module, max_tokens: int):
     total = _count_warmup_iterations(model, max_tokens)
     if total == 0:

vllm/tracing/__init__.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import functools
+from collections.abc import Callable
+from typing import Any, TypeAlias
+
+# Import the implementation details
+from .otel import (
+    SpanKind,
+    extract_trace_context,
+    init_otel_tracer,
+    init_otel_worker_tracer,
+    instrument_otel,
+    is_otel_available,
+    manual_instrument_otel,
+    otel_import_error_traceback,
+)
+from .utils import (
+    SpanAttributes,
+    contains_trace_headers,
+    extract_trace_headers,
+    log_tracing_disabled_warning,
+)
+
+__all__ = [
+    "instrument",
+    "instrument_manual",
+    "init_tracer",
+    "maybe_init_worker_tracer",
+    "is_tracing_available",
+    "SpanAttributes",
+    "SpanKind",
+    "extract_trace_context",
+    "extract_trace_headers",
+    "log_tracing_disabled_warning",
+    "contains_trace_headers",
+    "otel_import_error_traceback",
+]
+
+BackendAvailableFunc: TypeAlias = Callable[[], bool]
+InstrumentFunc: TypeAlias = Callable[..., Any]
+InstrumentManualFunc: TypeAlias = Callable[..., Any]
+InitTracerFunc: TypeAlias = Callable[..., Any]
+InitWorkerTracerFunc: TypeAlias = Callable[..., Any]
+_REGISTERED_TRACING_BACKENDS: dict[
+    str,
+    tuple[
+        BackendAvailableFunc,
+        InitTracerFunc,
+        InitWorkerTracerFunc,
+        InstrumentFunc,
+        InstrumentManualFunc,
+    ],
+] = {
+    "otel": (
+        is_otel_available,
+        init_otel_tracer,
+        init_otel_worker_tracer,
+        instrument_otel,
+        manual_instrument_otel,
+    ),
+}
+
+
+def init_tracer(
+    instrumenting_module_name: str,
+    otlp_traces_endpoint: str,
+    extra_attributes: dict[str, str] | None = None,
+):
+    is_available, init_tracer_fn, _, _, _ = _REGISTERED_TRACING_BACKENDS["otel"]
+    if is_available():
+        return init_tracer_fn(
+            instrumenting_module_name, otlp_traces_endpoint, extra_attributes
+        )
+
+
+def maybe_init_worker_tracer(
+    instrumenting_module_name: str,
+    process_kind: str,
+    process_name: str,
+):
+    is_available, _, init_worker_tracer_fn, _, _ = _REGISTERED_TRACING_BACKENDS["otel"]
+    if is_available():
+        return init_worker_tracer_fn(
+            instrumenting_module_name, process_kind, process_name
+        )
+
+
+def instrument(
+    obj: Callable | None = None,
+    *,
+    span_name: str = "",
+    attributes: dict[str, str] | None = None,
+    record_exception: bool = True,
+):
+    """
+    Generic decorator to instrument functions.
+    """
+    if obj is None:
+        return functools.partial(
+            instrument,
+            span_name=span_name,
+            attributes=attributes,
+            record_exception=record_exception,
+        )
+
+    # Dispatch to OTel (and potentially others later)
+    is_available, _, _, otel_instrument, _ = _REGISTERED_TRACING_BACKENDS["otel"]
+    if is_available():
+        return otel_instrument(
+            func=obj,
+            span_name=span_name,
+            attributes=attributes,
+            record_exception=record_exception,
+        )
+    else:
+        return obj
+
+
+def instrument_manual(
+    span_name: str,
+    start_time: int,
+    end_time: int | None = None,
+    attributes: dict[str, Any] | None = None,
+    context: Any = None,
+    kind: Any = None,
+):
+    """Manually create a span with explicit timestamps.
+
+    Args:
+        span_name: Name of the span to create.
+        start_time: Start time in nanoseconds since epoch.
+        end_time: Optional end time in nanoseconds. If None, ends immediately.
+        attributes: Optional dict of span attributes.
+        context: Optional trace context (e.g., from extract_trace_context).
+        kind: Optional SpanKind (e.g., SpanKind.SERVER).
+    """
+    is_available, _, _, _, manual_instrument_fn = _REGISTERED_TRACING_BACKENDS["otel"]
+    if is_available():
+        return manual_instrument_fn(
+            span_name, start_time, end_time, attributes, context, kind
+        )
+    else:
+        return None
+
+
+def is_tracing_available() -> bool:
+    """
+    Returns True if any tracing backend (OTel, Profiler, etc.) is available.
+    Use this to guard expensive tracing logic in the main code.
+    """
+    check_available = [
+        is_available
+        for is_available, _, _, _, _ in _REGISTERED_TRACING_BACKENDS.values()
+    ]
+    return any(check_available)

vllm/tracing/otel.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import atexit
+import functools
+import inspect
+import os
+import traceback
+from collections.abc import Mapping
+from contextlib import contextmanager
+from typing import Any
+
+from vllm.logger import init_logger
+from vllm.tracing.utils import TRACE_HEADERS, LoadingSpanAttributes
+
+logger = init_logger(__name__)
+
+try:
+    from opentelemetry import trace
+    from opentelemetry.context.context import Context
+    from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import (
+        OTLPSpanExporter as OTLPGrpcExporter,
+    )
+    from opentelemetry.exporter.otlp.proto.http.trace_exporter import (
+        OTLPSpanExporter as OTLPHttpExporter,
+    )
+    from opentelemetry.propagate import inject
+    from opentelemetry.sdk.environment_variables import (
+        OTEL_EXPORTER_OTLP_TRACES_PROTOCOL,
+    )
+    from opentelemetry.sdk.resources import Resource
+    from opentelemetry.sdk.trace import TracerProvider
+    from opentelemetry.sdk.trace.export import BatchSpanProcessor
+    from opentelemetry.trace import (
+        SpanKind,  # noqa: F401
+        Tracer,
+        set_tracer_provider,
+    )
+    from opentelemetry.trace.propagation.tracecontext import (
+        TraceContextTextMapPropagator,
+    )
+
+    _IS_OTEL_AVAILABLE = True
+    otel_import_error_traceback = None
+except ImportError:
+    _IS_OTEL_AVAILABLE = False
+    otel_import_error_traceback = traceback.format_exc()
+    trace = None  # type: ignore
+    Context = Any  # type: ignore
+    Tracer = Any  # type: ignore
+    inject = None  # type: ignore
+    Resource = None  # type: ignore
+    SpanKind = Any  # type: ignore
+
+
+def is_otel_available() -> bool:
+    return _IS_OTEL_AVAILABLE
+
+
+def init_otel_tracer(
+    instrumenting_module_name: str,
+    otlp_traces_endpoint: str,
+    extra_attributes: dict[str, str] | None = None,
+) -> Tracer:
+    """Initializes the OpenTelemetry tracer provider."""
+    if not _IS_OTEL_AVAILABLE:
+        raise ValueError(
+            "OpenTelemetry is not available. Unable to initialize "
+            "a tracer. Ensure OpenTelemetry packages are installed. "
+            f"Original error:\n{otel_import_error_traceback}"
+        )
+
+    # Store the endpoint in environment so child processes can inherit it
+    os.environ["OTEL_EXPORTER_OTLP_TRACES_ENDPOINT"] = otlp_traces_endpoint
+
+    resource_attrs = {}
+    resource_attrs["vllm.instrumenting_module_name"] = instrumenting_module_name
+    resource_attrs["vllm.process_id"] = str(os.getpid())
+    if extra_attributes:
+        resource_attrs.update(extra_attributes)
+    resource = Resource.create(resource_attrs)
+
+    trace_provider = TracerProvider(resource=resource)
+    span_exporter = get_span_exporter(otlp_traces_endpoint)
+    trace_provider.add_span_processor(BatchSpanProcessor(span_exporter))
+    set_tracer_provider(trace_provider)
+
+    atexit.register(trace_provider.shutdown)
+
+    tracer = trace_provider.get_tracer(instrumenting_module_name)
+    return tracer
+
+
+def get_span_exporter(endpoint):
+    protocol = os.environ.get(OTEL_EXPORTER_OTLP_TRACES_PROTOCOL, "grpc")
+    if protocol == "grpc":
+        exporter = OTLPGrpcExporter(endpoint=endpoint, insecure=True)
+    elif protocol == "http/protobuf":
+        exporter = OTLPHttpExporter(endpoint=endpoint)
+    else:
+        raise ValueError(f"Unsupported OTLP protocol '{protocol}' is configured")
+    return exporter
+
+
+def init_otel_worker_tracer(
+    instrumenting_module_name: str,
+    process_kind: str,
+    process_name: str,
+) -> Tracer:
+    """
+    Backend-specific initialization for OpenTelemetry in a worker process.
+    """
+    # Initialize the tracer if an OTLP endpoint is configured.
+    # The endpoint is propagated via environment variable from the main process.
+    otlp_endpoint = os.environ.get("OTEL_EXPORTER_OTLP_TRACES_ENDPOINT")
+    if not otlp_endpoint:
+        return None
+
+    extra_attrs = {
+        "vllm.process_kind": process_kind,
+        "vllm.process_name": process_name,
+    }
+
+    return init_otel_tracer(instrumenting_module_name, otlp_endpoint, extra_attrs)
+
+
+def extract_trace_context(headers: Mapping[str, str] | None) -> Context | None:
+    """Extracts context from HTTP headers."""
+    if _IS_OTEL_AVAILABLE and headers:
+        return TraceContextTextMapPropagator().extract(headers)
+    return None
+
+
+def instrument_otel(func, span_name, attributes, record_exception):
+    """Internal wrapper logic for sync and async functions."""
+
+    # Pre-calculate static code attributes once (these don't change)
+    code_attrs = {
+        LoadingSpanAttributes.CODE_FUNCTION: func.__qualname__,
+        LoadingSpanAttributes.CODE_NAMESPACE: func.__module__,
+        LoadingSpanAttributes.CODE_FILEPATH: func.__code__.co_filename,
+        LoadingSpanAttributes.CODE_LINENO: str(func.__code__.co_firstlineno),
+    }
+    if attributes:
+        code_attrs.update(attributes)
+
+    final_span_name = span_name or func.__qualname__
+    module_name = func.__module__
+
+    @functools.wraps(func)
+    async def async_wrapper(*args, **kwargs):
+        tracer = trace.get_tracer(module_name)
+        ctx = _get_smart_context()
+        with (
+            tracer.start_as_current_span(
+                final_span_name,
+                context=ctx,
+                attributes=code_attrs,
+                record_exception=record_exception,
+            ),
+            propagate_trace_to_env(),
+        ):
+            return await func(*args, **kwargs)
+
+    @functools.wraps(func)
+    def sync_wrapper(*args, **kwargs):
+        tracer = trace.get_tracer(module_name)
+        ctx = _get_smart_context()
+        with (
+            tracer.start_as_current_span(
+                final_span_name,
+                context=ctx,
+                attributes=code_attrs,
+                record_exception=record_exception,
+            ),
+            propagate_trace_to_env(),
+        ):
+            return func(*args, **kwargs)
+
+    return async_wrapper if inspect.iscoroutinefunction(func) else sync_wrapper
+
+
+def manual_instrument_otel(
+    span_name: str,
+    start_time: int,
+    end_time: int | None = None,
+    attributes: dict[str, Any] | None = None,
+    context: Context | None = None,
+    kind: Any = None,  # SpanKind, but typed as Any for when OTEL unavailable
+):
+    """Manually create and end a span with explicit timestamps."""
+    if not _IS_OTEL_AVAILABLE:
+        return
+
+    tracer = trace.get_tracer(__name__)
+    # Use provided context, or fall back to smart context detection
+    ctx = context if context is not None else _get_smart_context()
+
+    span_kwargs: dict[str, Any] = {
+        "name": span_name,
+        "context": ctx,
+        "start_time": start_time,
+    }
+    if kind is not None:
+        span_kwargs["kind"] = kind
+
+    span = tracer.start_span(**span_kwargs)
+    if attributes:
+        span.set_attributes(attributes)
+    if end_time is not None:
+        span.end(end_time=end_time)
+    else:
+        span.end()
+
+
+def _get_smart_context() -> Context | None:
+    """
+    Determines the parent context.
+    1. If a Span is already active in this process, use it.
+    2. If not, extract from os.environ, handling the case-sensitivity mismatch.
+    """
+    current_span = trace.get_current_span()
+    if current_span.get_span_context().is_valid:
+        return None
+
+    carrier = {}
+
+    if tp := os.environ.get("traceparent", os.environ.get("TRACEPARENT")):  # noqa: SIM112
+        carrier["traceparent"] = tp
+
+    if ts := os.environ.get("tracestate", os.environ.get("TRACESTATE")):  # noqa: SIM112
+        carrier["tracestate"] = ts
+
+    if not carrier:
+        carrier = dict(os.environ)
+
+    return TraceContextTextMapPropagator().extract(carrier)
+
+
+@contextmanager
+def propagate_trace_to_env():
+    """
+    Temporarily injects the current OTel context into os.environ.
+    This ensures that any subprocesses (like vLLM workers) spawned
+    within this context inherit the correct traceparent.
+    """
+    if not _IS_OTEL_AVAILABLE:
+        yield
+        return
+
+    # Capture original state of relevant keys
+    original_state = {k: os.environ.get(k) for k in TRACE_HEADERS}
+
+    try:
+        # inject() writes 'traceparent' and 'tracestate' to os.environ
+        inject(os.environ)
+        yield
+
+    finally:
+        # Restore original environment
+        for key, original_value in original_state.items():
+            if original_value is None:
+                os.environ.pop(key, None)
+            else:
+                os.environ[key] = original_value

vllm/tracing.py → vllm/tracing/utils.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-import os
 from collections.abc import Mapping
 
 from vllm.logger import init_logger
 from vllm.utils.func_utils import run_once
 
-TRACE_HEADERS = ["traceparent", "tracestate"]
-
 logger = init_logger(__name__)
 
-_is_otel_imported = False
-otel_import_error_traceback: str | None = None
-try:
-    from opentelemetry.context.context import Context
-    from opentelemetry.sdk.environment_variables import (
-        OTEL_EXPORTER_OTLP_TRACES_PROTOCOL,
-    )
-    from opentelemetry.sdk.trace import TracerProvider
-    from opentelemetry.sdk.trace.export import BatchSpanProcessor
-    from opentelemetry.trace import SpanKind, Tracer, set_tracer_provider
-    from opentelemetry.trace.propagation.tracecontext import (
-        TraceContextTextMapPropagator,
-    )
-
-    _is_otel_imported = True
-except ImportError:
-    # Capture and format traceback to provide detailed context for the import
-    # error. Only the string representation of the error is retained to avoid
-    # memory leaks.
-    # See https://github.com/vllm-project/vllm/pull/7266#discussion_r1707395458
-    import traceback
-
-    otel_import_error_traceback = traceback.format_exc()
-
-    class Context:  # type: ignore
-        pass
-
-    class BaseSpanAttributes:  # type: ignore
-        pass
-
-    class SpanKind:  # type: ignore
-        pass
-
-    class Tracer:  # type: ignore
-        pass
-
-
-def is_otel_available() -> bool:
-    return _is_otel_imported
-
-
-def init_tracer(
-    instrumenting_module_name: str, otlp_traces_endpoint: str
-) -> Tracer | None:
-    if not is_otel_available():
-        raise ValueError(
-            "OpenTelemetry is not available. Unable to initialize "
-            "a tracer. Ensure OpenTelemetry packages are installed. "
-            f"Original error:\n{otel_import_error_traceback}"
-        )
-    trace_provider = TracerProvider()
-
-    span_exporter = get_span_exporter(otlp_traces_endpoint)
-    trace_provider.add_span_processor(BatchSpanProcessor(span_exporter))
-    set_tracer_provider(trace_provider)
-
-    tracer = trace_provider.get_tracer(instrumenting_module_name)
-    return tracer
-
-
-def get_span_exporter(endpoint):
-    protocol = os.environ.get(OTEL_EXPORTER_OTLP_TRACES_PROTOCOL, "grpc")
-    if protocol == "grpc":
-        from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import (
-            OTLPSpanExporter,
-        )
-    elif protocol == "http/protobuf":
-        from opentelemetry.exporter.otlp.proto.http.trace_exporter import (
-            OTLPSpanExporter,  # type: ignore
-        )
-    else:
-        raise ValueError(f"Unsupported OTLP protocol '{protocol}' is configured")
-
-    return OTLPSpanExporter(endpoint=endpoint)
-
-
-def extract_trace_context(headers: Mapping[str, str] | None) -> Context | None:
-    if is_otel_available():
-        headers = headers or {}
-        return TraceContextTextMapPropagator().extract(headers)
-    else:
-        return None
+# Standard W3C headers used for context propagation
+TRACE_HEADERS = ["traceparent", "tracestate"]
 
 
-def extract_trace_headers(headers: Mapping[str, str]) -> Mapping[str, str]:
-    return {h: headers[h] for h in TRACE_HEADERS if h in headers}
+class SpanAttributes:
+    """
+    Standard attributes for spans.
 
+    These are largely based on OpenTelemetry Semantic Conventions but are defined
+    here as constants so they can be used by any backend or logger.
+    """
 
-class SpanAttributes:
-    # Attribute names copied from here to avoid version conflicts:
-    # https://github.com/open-telemetry/semantic-conventions/blob/main/docs/gen-ai/gen-ai-spans.md
+    # Attribute names copied from OTel semantic conventions to avoid version conflicts
     GEN_AI_USAGE_COMPLETION_TOKENS = "gen_ai.usage.completion_tokens"
     GEN_AI_USAGE_PROMPT_TOKENS = "gen_ai.usage.prompt_tokens"
     GEN_AI_REQUEST_MAX_TOKENS = "gen_ai.request.max_tokens"
     GEN_AI_REQUEST_TOP_P = "gen_ai.request.top_p"
     GEN_AI_REQUEST_TEMPERATURE = "gen_ai.request.temperature"
     GEN_AI_RESPONSE_MODEL = "gen_ai.response.model"
-    # Attribute names added until they are added to the semantic conventions:
+
+    # Custom attributes added until they are standardized
     GEN_AI_REQUEST_ID = "gen_ai.request.id"
     GEN_AI_REQUEST_N = "gen_ai.request.n"
     GEN_AI_USAGE_NUM_SEQUENCES = "gen_ai.usage.num_sequences"
@@ -116,20 +36,37 @@ class SpanAttributes:
     GEN_AI_LATENCY_TIME_TO_FIRST_TOKEN = "gen_ai.latency.time_to_first_token"
     GEN_AI_LATENCY_E2E = "gen_ai.latency.e2e"
     GEN_AI_LATENCY_TIME_IN_SCHEDULER = "gen_ai.latency.time_in_scheduler"
-    # Time taken in the forward pass for this across all workers
+
+    # Latency breakdowns
     GEN_AI_LATENCY_TIME_IN_MODEL_FORWARD = "gen_ai.latency.time_in_model_forward"
-    # Time taken in the model execute function. This will include model
-    # forward, block/sync across workers, cpu-gpu sync time and sampling time.
     GEN_AI_LATENCY_TIME_IN_MODEL_EXECUTE = "gen_ai.latency.time_in_model_execute"
     GEN_AI_LATENCY_TIME_IN_MODEL_PREFILL = "gen_ai.latency.time_in_model_prefill"
     GEN_AI_LATENCY_TIME_IN_MODEL_DECODE = "gen_ai.latency.time_in_model_decode"
     GEN_AI_LATENCY_TIME_IN_MODEL_INFERENCE = "gen_ai.latency.time_in_model_inference"
 
 
+class LoadingSpanAttributes:
+    """Custom attributes for code-level tracing (file, line number)."""
+
+    CODE_NAMESPACE = "code.namespace"
+    CODE_FUNCTION = "code.function"
+    CODE_FILEPATH = "code.filepath"
+    CODE_LINENO = "code.lineno"
+
+
 def contains_trace_headers(headers: Mapping[str, str]) -> bool:
+    """Check if the provided headers dictionary contains trace context."""
     return any(h in headers for h in TRACE_HEADERS)
 
 
+def extract_trace_headers(headers: Mapping[str, str]) -> Mapping[str, str]:
+    """
+    Extract only trace-related headers from a larger header dictionary.
+    Useful for logging or passing context to a non-OTel client.
+    """
+    return {h: headers[h] for h in TRACE_HEADERS if h in headers}
+
+
 @run_once
 def log_tracing_disabled_warning() -> None:
     logger.warning("Received a request with trace context but tracing is disabled")

vllm/v1/engine/async_llm.py

@@ -110,6 +110,10 @@ class AsyncLLM(EngineClient):
         self.model_config = vllm_config.model_config
         self.vllm_config = vllm_config
         self.observability_config = vllm_config.observability_config
+        tracing_endpoint = self.observability_config.otlp_traces_endpoint
+        if tracing_endpoint is not None:
+            init_tracer("vllm.llm_engine", tracing_endpoint)
+
         self.log_requests = log_requests
 
         custom_stat_loggers = list(stat_loggers or [])
@@ -136,10 +140,8 @@ class AsyncLLM(EngineClient):
             log_stats=self.log_stats,
             stream_interval=self.vllm_config.scheduler_config.stream_interval,
         )
-        endpoint = self.observability_config.otlp_traces_endpoint
-        if endpoint is not None:
-            tracer = init_tracer("vllm.llm_engine", endpoint)
-            self.output_processor.tracer = tracer
+        if tracing_endpoint is not None:
+            self.output_processor.tracing_enabled = True
 
         # EngineCore (starts the engine in background process).
         self.engine_core = EngineCoreClient.make_async_mp_client(

vllm/v1/engine/core.py

@@ -24,6 +24,7 @@ from vllm.logging_utils.dump_input import dump_engine_exception
 from vllm.lora.request import LoRARequest
 from vllm.multimodal import MULTIMODAL_REGISTRY
 from vllm.tasks import POOLING_TASKS, SupportedTask
+from vllm.tracing import instrument, maybe_init_worker_tracer
 from vllm.transformers_utils.config import maybe_register_config_serialize_by_value
 from vllm.utils.gc_utils import (
     freeze_gc_heap,
@@ -217,6 +218,7 @@ class EngineCore:
         # environment variable overrides after this point)
         enable_envs_cache()
 
+    @instrument(span_name="Prepare model")
     def _initialize_kv_caches(
         self, vllm_config: VllmConfig
     ) -> tuple[int, int, KVCacheConfig]:
@@ -658,6 +660,7 @@ class EngineCoreProc(EngineCore):
 
     ENGINE_CORE_DEAD = b"ENGINE_CORE_DEAD"
 
+    @instrument(span_name="EngineCoreProc init")
     def __init__(
         self,
         vllm_config: VllmConfig,
@@ -926,8 +929,18 @@ class EngineCoreProc(EngineCore):
             data_parallel = parallel_config.data_parallel_size > 1 or dp_rank > 0
             if data_parallel:
                 parallel_config.data_parallel_rank_local = local_dp_rank
+                maybe_init_worker_tracer(
+                    instrumenting_module_name="vllm.engine_core",
+                    process_kind="engine_core",
+                    process_name=f"EngineCore_DP{dp_rank}",
+                )
                 set_process_title("EngineCore", f"DP{dp_rank}")
             else:
+                maybe_init_worker_tracer(
+                    instrumenting_module_name="vllm.engine_core",
+                    process_kind="engine_core",
+                    process_name="EngineCore",
+                )
                 set_process_title("EngineCore")
             decorate_logs()
 
@@ -956,6 +969,7 @@ class EngineCoreProc(EngineCore):
                 parallel_config.data_parallel_rank = 0
                 engine_core = EngineCoreProc(*args, engine_index=dp_rank, **kwargs)
 
+            assert engine_core is not None
             engine_core.run_busy_loop()
 
         except SystemExit:
@@ -1485,6 +1499,13 @@ class EngineCoreActorMixin:
         dp_rank: int = 0,
         local_dp_rank: int = 0,
     ):
+        # Initialize tracer for distributed tracing if configured.
+        maybe_init_worker_tracer(
+            instrumenting_module_name="vllm.engine_core",
+            process_kind="engine_core",
+            process_name=f"DPEngineCoreActor_DP{dp_rank}",
+        )
+
         self.addresses = addresses
         vllm_config.parallel_config.data_parallel_index = dp_rank
         vllm_config.parallel_config.data_parallel_rank_local = local_dp_rank

vllm/v1/engine/core_client.py

@@ -24,6 +24,7 @@ from vllm.envs import VLLM_ENGINE_READY_TIMEOUT_S
 from vllm.logger import init_logger
 from vllm.lora.request import LoRARequest
 from vllm.tasks import SupportedTask
+from vllm.tracing import instrument
 from vllm.utils.async_utils import in_loop
 from vllm.utils.network_utils import (
     close_sockets,
@@ -96,6 +97,7 @@ class EngineCoreClient(ABC):
         return InprocClient(vllm_config, executor_class, log_stats)
 
     @staticmethod
+    @instrument(span_name="Overall Loading")
     def make_async_mp_client(
         vllm_config: VllmConfig,
         executor_class: type[Executor],
@@ -650,6 +652,7 @@ def _process_utility_output(
 class SyncMPClient(MPClient):
     """Synchronous client for multi-proc EngineCore."""
 
+    @instrument(span_name="SyncMPClient init")
     def __init__(
         self, vllm_config: VllmConfig, executor_class: type[Executor], log_stats: bool
     ):
@@ -819,6 +822,7 @@ class SyncMPClient(MPClient):
 class AsyncMPClient(MPClient):
     """Asyncio-compatible client for multi-proc EngineCore."""
 
+    @instrument(span_name="AsyncMPClient init")
     def __init__(
         self,
         vllm_config: VllmConfig,