add Starlette middleware support

src/litserve/server.py

@@ -113,16 +113,25 @@ def __init__(
         stream: bool = False,
         spec: Optional[LitSpec] = None,
         max_payload_size=None,
-        middlewares: Optional[list[tuple[Callable, dict]]] = None,
+        middlewares: Optional[list[Union[Callable, tuple[Callable, dict]]]] = None,
     ):
         if batch_timeout > timeout and timeout not in (False, -1):
             raise ValueError("batch_timeout must be less than timeout")
         if max_batch_size <= 0:
             raise ValueError("max_batch_size must be greater than 0")
         if isinstance(spec, OpenAISpec):
             stream = True
+
         if middlewares is None:
             middlewares = []
+        if not isinstance(middlewares, list):
+            _msg = (
+                "middlewares must be a list of tuples"
+                " where each tuple contains a middleware and its arguments. For example:\n"
+                "server = ls.LitServer(ls.examples.SimpleLitAPI(), "
+                'middlewares=[(RequestIdMiddleware, {"length": 5})])'
+            )
+            raise ValueError(_msg)
 
         if not api_path.startswith("/"):
             raise ValueError(
@@ -364,8 +373,12 @@ async def stream_predict(request: self.request_type) -> self.response_type:
                     path, endpoint=endpoint, methods=methods, dependencies=[Depends(self.setup_auth())]
                 )
 
-        for middleware, kwargs in self.middlewares:
-            self.app.add_middleware(middleware, **kwargs)
+        for middleware in self.middlewares:
+            if isinstance(middleware, tuple):
+                middleware, kwargs = middleware
+                self.app.add_middleware(middleware, **kwargs)
+            elif callable(middleware):
+                self.app.add_middleware(middleware)
 
     @staticmethod
     def generate_client_file():

tests/test_lit_server.py

@@ -23,6 +23,8 @@
 import torch.nn as nn
 from httpx import AsyncClient
 from litserve.utils import wrap_litserve_start
+from starlette.middleware.httpsredirect import HTTPSRedirectMiddleware
+from starlette.middleware.trustedhost import TrustedHostMiddleware
 
 from unittest.mock import patch, MagicMock
 import pytest
@@ -393,3 +395,37 @@ def test_custom_middleware():
         assert response.status_code == 200, f"Expected response to be 200 but got {response.status_code}"
         assert response.json() == {"output": 16.0}, "server didn't return expected output"
         assert response.headers["X-Request-Id"] == "00000"
+
+
+def test_starlette_middlewares():
+    middlewares = [
+        (
+            TrustedHostMiddleware,
+            {
+                "allowed_hosts": ["localhost", "127.0.0.1"],
+            },
+        ),
+        HTTPSRedirectMiddleware,
+    ]
+    server = ls.LitServer(ls.examples.SimpleLitAPI(), middlewares=middlewares)
+    with wrap_litserve_start(server) as server, TestClient(server.app) as client:
+        response = client.post("/predict", json={"input": 4.0}, headers={"Host": "localhost"})
+        assert response.status_code == 200, f"Expected response to be 200 but got {response.status_code}"
+        assert response.json() == {"output": 16.0}, "server didn't return expected output"
+
+        response = client.post("/predict", json={"input": 4.0}, headers={"Host": "not-trusted-host"})
+        assert response.status_code == 400, f"Expected response to be 400 but got {response.status_code}"
+
+
+def test_middlewares_inputs():
+    server = ls.LitServer(SimpleLitAPI(), middlewares=[])
+    assert len(server.middlewares) == 1, "Default middleware should be present"
+
+    server = ls.LitServer(ls.examples.SimpleLitAPI(), middlewares=[], max_payload_size=1000)
+    assert len(server.middlewares) == 2, "Default middleware should be present"
+
+    server = ls.LitServer(ls.examples.SimpleLitAPI(), middlewares=None)
+    assert len(server.middlewares) == 1, "Default middleware should be present"
+
+    with pytest.raises(ValueError, match="middlewares must be a list of tuples"):
+        ls.LitServer(ls.examples.SimpleLitAPI(), middlewares=(RequestIdMiddleware, {"length": 5}))