[PD] let toy proxy handle /chat/completions (#19730)

Signed-off-by: Linkun <github@lkchen.net>

tests/v1/kv_connector/nixl_integration/toy_proxy_server.py

@@ -196,8 +196,7 @@ async def stream_service_response(client_info: dict, endpoint: str,
             yield chunk
 
 
-@app.post("/v1/completions")
-async def handle_completions(request: Request):
+async def _handle_completions(api: str, request: Request):
     try:
         req_data = await request.json()
         request_id = str(uuid.uuid4())
@@ -206,9 +205,8 @@ async def handle_completions(request: Request):
         prefill_client_info = get_next_client(request.app, 'prefill')
 
         # Send request to prefill service
-        response = await send_request_to_service(prefill_client_info,
-                                                 "/completions", req_data,
-                                                 request_id)
+        response = await send_request_to_service(prefill_client_info, api,
+                                                 req_data, request_id)
 
         # Extract the needed fields
         response_json = response.json()
@@ -224,7 +222,7 @@ async def handle_completions(request: Request):
         # Stream response from decode service
         async def generate_stream():
             async for chunk in stream_service_response(decode_client_info,
-                                                       "/completions",
+                                                       api,
                                                        req_data,
                                                        request_id=request_id):
                 yield chunk
@@ -237,12 +235,22 @@ async def handle_completions(request: Request):
         import traceback
         exc_info = sys.exc_info()
         print("Error occurred in disagg prefill proxy server"
-              " - completions endpoint")
+              f" - {api} endpoint")
         print(e)
         print("".join(traceback.format_exception(*exc_info)))
         raise
 
 
+@app.post("/v1/completions")
+async def handle_completions(request: Request):
+    return await _handle_completions("/completions", request)
+
+
+@app.post("/v1/chat/completions")
+async def handle_chat_completions(request: Request):
+    return await _handle_completions("/chat/completions", request)
+
+
 @app.get("/healthcheck")
 async def healthcheck():
     """Simple endpoint to check if the server is running."""