support serving engine switch in pf serve cmd

src/promptflow-devkit/promptflow/_cli/_pf/_flow.py

@@ -199,6 +199,9 @@ def add_parser_serve_flow(subparsers):
  add_param_skip_browser = lambda parser: parser.add_argument( # noqa: E731
  "--skip-open-browser", action="store_true", default=False, help="Skip open browser for flow serving."
  )
+ add_param_engine = lambda parser: parser.add_argument( # noqa: E731
+ "--engine", type=str, default="flask", help="The engine to serve the flow, can be flask or fastapi."
+ )
  activate_action(
  name="serve",
  description="Serving a flow as an endpoint.",
@@ -207,6 +210,7 @@ def add_parser_serve_flow(subparsers):
  add_param_source,
  add_param_port,
  add_param_host,
+ add_param_engine,
  add_param_static_folder,
  add_param_environment_variables,
  add_param_config,
@@ -595,6 +599,7 @@ def serve_flow(args):
  host=args.host,
  port=args.port,
  skip_open_browser=args.skip_open_browser,
+ engine=args.engine,
  )
  logger.info("Promptflow app ended")
 

src/promptflow-devkit/promptflow/_sdk/_utilities/serve_utils.py

@@ -58,6 +58,7 @@ def start_flow_service(
  environment_variables: Dict[str, str] = None,
  init: Dict[str, Any] = None,
  skip_open_browser: bool = True,
+ engine: str = "flask",
 ):
  logger.info(
  "Start promptflow server with port %s",
@@ -72,6 +73,11 @@ def start_flow_service(
  message_format="Support directory `source` for Python flow only for now, but got {source}.",
  source=source,
  )
+ if engine not in ["flask", "fastapi"]:
+ raise UserErrorException(
+ message_format="Unsupported engine {engine} for Python flow, only support 'flask' and 'fastapi'.",
+ engine=engine,
+ )
  serve_python_flow(
  flow_file_name=flow_file_name,
  flow_dir=flow_dir,
@@ -82,6 +88,7 @@ def start_flow_service(
  config=config or {},
  environment_variables=environment_variables or {},
  skip_open_browser=skip_open_browser,
+ engine=engine,
  )
  else:
  serve_csharp_flow(
@@ -103,6 +110,7 @@ def serve_python_flow(
  environment_variables,
  init,
  skip_open_browser: bool,
+ engine,
 ):
  from promptflow._sdk._configuration import Configuration
  from promptflow.core._serving.app import create_app
@@ -121,13 +129,24 @@ def serve_python_flow(
  environment_variables=environment_variables,
  connection_provider=connection_provider,
  init=init,
+ engine=engine,
  )
  if not skip_open_browser:
  target = f"http://{host}:{port}"
  logger.info(f"Opening browser {target}...")
  webbrowser.open(target)
- # Debug is not supported for now as debug will rerun command, and we changed working directory.
- app.run(port=port, host=host)
+ if engine == "flask":
+ # Debug is not supported for now as debug will rerun command, and we changed working directory.
+ app.run(port=port, host=host)
+ else:
+ try:
+ import uvicorn
+
+ uvicorn.run(app, host=host, port=port)
+ except ImportError:
+ raise UserErrorException(
+ message_format="FastAPI engine requires uvicorn, please install uvicorn by `pip install uvicorn`."
+ )
 
 
 @contextlib.contextmanager