[metrics] instrument fastapi for tracing

docs/references/production_request_trace.md

@@ -12,7 +12,7 @@ This section explains how to configure the request tracing and export the trace
     pip install -e "python[tracing]"
 
     # or manually install the dependencies using pip
-    pip install opentelemetry-sdk opentelemetry-api opentelemetry-exporter-otlp opentelemetry-exporter-otlp-proto-grpc
+    pip install opentelemetry-sdk opentelemetry-api opentelemetry-exporter-otlp opentelemetry-exporter-otlp-proto-grpc opentelemetry-instrumentation-fastapi
     ```
 
 2. launch opentelemetry collector and jaeger

python/pyproject.toml

@@ -88,6 +88,7 @@ tracing = [
     "opentelemetry-api",
     "opentelemetry-exporter-otlp",
     "opentelemetry-exporter-otlp-proto-grpc",
+    "opentelemetry-instrumentation-fastapi",
 ]
 all = ["sglang[test]", "sglang[decord]"]
 blackwell = ["sglang[test]", "sglang[decord]"]

python/sglang/srt/entrypoints/http_server.py

@@ -29,7 +29,11 @@
 from http import HTTPStatus
 from typing import Any, AsyncIterator, Callable, Dict, List, Optional, Union
 
-from sglang.srt.tracing.trace import process_tracing_init, trace_set_thread_info
+from sglang.srt.tracing.trace import (
+    instrument_fastapi,
+    process_tracing_init,
+    trace_set_thread_info,
+)
 
 # Fix a bug of Python threading
 setattr(threading, "_register_atexit", lambda *args, **kwargs: None)
@@ -1183,6 +1187,9 @@ async def vertex_generate(vertex_req: VertexGenerateReqInput, raw_request: Reque
     return ORJSONResponse({"predictions": ret})
 
 
+instrument_fastapi(app)
+
+
 def _update_weight_version_if_provided(weight_version: Optional[str]) -> None:
     """Update weight version if provided."""
     if weight_version is not None:

python/sglang/srt/tracing/trace.py

@@ -25,13 +25,16 @@
 from dataclasses import dataclass
 from typing import Any, Dict, List, Optional
 
+from fastapi import FastAPI
+
 logger = logging.getLogger(__name__)
 opentelemetry_imported = False
 tracing_enabled = False
 
 try:
     from opentelemetry import context, propagate, trace
     from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
+    from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
     from opentelemetry.sdk.resources import SERVICE_NAME, Resource
     from opentelemetry.sdk.trace import TracerProvider, id_generator
     from opentelemetry.sdk.trace.export import BatchSpanProcessor
@@ -550,3 +553,10 @@ def trace_slice_add_attr(rid: str, attrs: Dict[str, Any]):
 
     slice_info = thread_context.cur_slice_stack[-1]
     slice_info.span.set_attributes(attrs)
+
+
+def instrument_fastapi(app: FastAPI):
+    if not opentelemetry_imported:
+        return
+
+    FastAPIInstrumentor.instrument_app(app)