Add example middleware for langsmith tracing

backend/server/main.py

@@ -14,6 +14,7 @@
     ExtractResponse,
     extraction_runnable,
 )
+from server.middleware import add_langsmith_tracing
 
 logger = logging.getLogger(__name__)
 
@@ -30,6 +31,9 @@
 )
 
 
+add_langsmith_tracing = app.middleware("http")(add_langsmith_tracing)
+
+
 ROOT = Path(__file__).parent.parent
 
 ORIGINS = os.environ.get("CORS_ORIGINS", "").split(",")

backend/server/middleware.py

@@ -0,0 +1,31 @@
+"""Add example middleware to enable langsmith tracing on selected endpoints.
+
+This enables langsmith tracing on selected endpoints, showing how to add
+tags and metadata to the traces.
+"""
+from urllib.parse import urlparse
+
+from langchain_core.tracers.context import tracing_v2_enabled
+from langsmith import trace
+from starlette.requests import Request
+
+
+async def add_langsmith_tracing(request: Request, call_next):
+    """Add langsmith middleware"""
+    with tracing_v2_enabled():
+        parsed_url = urlparse(str(request.url))
+        if parsed_url.path not in {"/suggest", "/extract", "/extract/shared"}:
+            # Skip tracing for all other endpoints
+            return await call_next(request)
+
+        method = request.method
+
+        with trace(
+            name=parsed_url.path,
+            tags=[method],
+            metadata={
+                "__useragent": request.headers.get("user-agent"),
+            },
+        ):
+            response = await call_next(request)
+    return response