patch: name used for tracing should take into account APIRouter path (#…

…476)

If there is a router at path /foo, and a runnable is added to that
router at
path /bar, the name of the runnable should be /foo/bar for logging
purposes.

examples/router/server.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+"""Example LangChain Server that uses a Fast API Router.
+
+When applications grow, it becomes useful to use FastAPI's Router to organize
+the routes.
+
+See more documentation at:
+
+https://fastapi.tiangolo.com/tutorial/bigger-applications/
+"""
+from fastapi import APIRouter, FastAPI
+from langchain.chat_models import ChatAnthropic, ChatOpenAI
+
+from langserve import add_routes
+
+app = FastAPI()
+
+router = APIRouter(prefix="/models")
+
+# Invocations to this router will appear in trace logs as /models/openai
+add_routes(
+    router,
+    ChatOpenAI(),
+    path="/openai",
+)
+# Invocations to this router will appear in trace logs as /models/anthropic
+add_routes(
+    router,
+    ChatAnthropic(),
+    path="/anthropic",
+)
+
+app.include_router(router)
+
+if __name__ == "__main__":
+    import uvicorn
+
+    uvicorn.run(app, host="localhost", port=8000)

langserve/api_handler.py

@@ -171,7 +171,7 @@ async def _unpack_request_config(
 
 
 def _update_config_with_defaults(
-    path: str,
+    run_name: str,
     incoming_config: RunnableConfig,
     request: Request,
     *,
@@ -209,7 +209,7 @@ def _update_config_with_defaults(
         metadata.update(hosted_metadata)
 
     non_overridable_default_config = RunnableConfig(
-        run_name=path,
+        run_name=run_name,
         metadata=metadata,
     )
 
@@ -536,6 +536,14 @@ def __init__(
 
         self._path = path
         self._base_url = prefix + path
+        # Setting the run name explicitly
+        # the run name is set to the base url, which takes into account
+        # the prefix (e.g., if there's an APIRouter used) and the path relative
+        # to the router.
+        # If the base path is /foo/bar, the run name will be /foo/bar
+        # and when tracing information is logged, we'll be able to see
+        # traces for the path /foo/bar.
+        self._run_name = self._base_url
         self._include_callback_events = include_callback_events
         self._per_req_config_modifier = per_req_config_modifier
         self._serializer = WellKnownLCSerializer()
@@ -663,7 +671,7 @@ async def _get_config_and_input(
                 server_config=server_config,
             )
             config = _update_config_with_defaults(
-                self._path,
+                self._run_name,
                 user_provided_config,
                 request,
                 endpoint=endpoint,
@@ -814,7 +822,7 @@ async def batch(
             _add_callbacks(config_, [aggregator])
             final_configs.append(
                 _update_config_with_defaults(
-                    self._path, config_, request, endpoint="batch"
+                    self._run_name, config_, request, endpoint="batch"
                 )
             )
 
@@ -1236,7 +1244,7 @@ async def input_schema(
                 server_config=server_config,
             )
             config = _update_config_with_defaults(
-                self._path, user_provided_config, request
+                self._run_name, user_provided_config, request
             )
 
         return self._runnable.get_input_schema(config).schema()
@@ -1264,7 +1272,7 @@ async def output_schema(
                 server_config=server_config,
             )
             config = _update_config_with_defaults(
-                self._path, user_provided_config, request
+                self._run_name, user_provided_config, request
             )
         return self._runnable.get_output_schema(config).schema()
 
@@ -1291,7 +1299,7 @@ async def config_schema(
                 server_config=server_config,
             )
             config = _update_config_with_defaults(
-                self._path, user_provided_config, request
+                self._run_name, user_provided_config, request
             )
         return (
             self._runnable.with_config(config)