run LitServe with minimal dependency (#138)

* make minimal dependency

* add test

* fix

* fix test

* fix

* add license

.github/workflows/ci-minimal-dependency-check.yml

@@ -0,0 +1,33 @@
+name: Minimal dependency check
+
+on:
+  push:
+    branches: [main, "release/*"]
+  pull_request:
+    branches: [main, "release/*"]
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  pytester:
+    runs-on: ubuntu-latest
+
+    timeout-minutes: 30
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: 3.9
+
+      - name: Install LitServe
+        run: |
+          pip --version
+          pip install . psutil  -U -q
+          pip list
+
+      - name: Tests
+        run: python tests/minimal_run.py

src/litserve/connector.py

@@ -72,12 +72,17 @@ def _auto_device_count(self, accelerator) -> int:
 
     @staticmethod
     def _choose_gpu_accelerator_backend():
-        import torch
-
         if check_cuda_with_nvidia_smi() > 0:
             return "cuda"
-        if torch.backends.mps.is_available() and platform.processor() in ("arm", "arm64"):
-            return "mps"
+
+        try:
+            import torch
+
+            if torch.backends.mps.is_available() and platform.processor() in ("arm", "arm64"):
+                return "mps"
+        except ImportError:
+            return None
+
         return None
 
 

tests/minimal_run.py

@@ -0,0 +1,46 @@
+# Copyright The Lightning AI team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import subprocess
+import psutil
+import time
+import json
+import urllib.request
+
+
+def main():
+    process = subprocess.Popen(
+        ["python", "tests/simple_server.py"],
+    )
+    print("Waiting for server to start...")
+    time.sleep(5)
+    try:
+        url = "http://127.0.0.1:8000/predict"
+        data = json.dumps({"input": 4.0}).encode("utf-8")
+        headers = {"Content-Type": "application/json"}
+        request = urllib.request.Request(url, data=data, headers=headers, method="POST")
+        response = urllib.request.urlopen(request)
+        status_code = response.getcode()
+        assert status_code == 200
+    except Exception:
+        raise
+
+    finally:
+        parent = psutil.Process(process.pid)
+        for child in parent.children(recursive=True):
+            child.kill()
+        process.kill()
+
+
+if __name__ == "__main__":
+    main()