[Bugfix][Router] Accept single-label static backend URLs

src/tests/test_utils.py

@@ -8,6 +8,40 @@
 from vllm_router import utils
 
 
+@pytest.mark.parametrize(
+    "url,expected_result",
+    (
+        ("http://oss-20b:8000", True),
+        ("http://oss-20b/v1", True),
+        ("http://oss_20b:8000", True),
+        ("https://x:8000", True),
+        ("http://-host:8000", False),
+        ("http://host-:8000/v1", False),
+        ("https://example.com:8000/v1", True),
+        ("http://oss_20b.example.com:8000", True),
+        ("http://oss-20b.example.com:8000", True),
+        # Preserve existing multi-label acceptance.
+        ("http://-host.example.com:8000", True),
+        ("http://host-.example.com:8000", True),
+        ("http://localhost:8000", True),
+        ("http://127.0.0.1:8000", True),
+        ("", False),
+        ("ftp://localhost:8000", False),
+        ("http://host..example.com:8000", False),
+        ("http://host:", False),
+        ("http://[::1]:8000", False),
+    ),
+)
+def test_validate_url(url: str, expected_result: bool) -> None:
+    assert utils.validate_url(url) is expected_result
+
+
+def test_parse_static_urls_keeps_single_label_backends() -> None:
+    assert utils.parse_static_urls(
+        "http://oss-20b:8000,http://-host:8000,http://oss_20b/v1,http://localhost:8000"
+    ) == ["http://oss-20b:8000", "http://oss_20b/v1", "http://localhost:8000"]
+
+
 @pytest.mark.parametrize(
     "aliases,expected_result",
     (

src/vllm_router/utils.py

@@ -171,7 +171,7 @@ def validate_url(url: str) -> bool:
     regex = re.compile(
         r"^(http|https)://"  # Protocol
         r"(([a-zA-Z0-9_-]+\.)+[a-zA-Z]{2,}|"  # Domain name
-        r"localhost|"  # Or localhost
+        r"(?!-)[a-zA-Z0-9_-]+(?<!-)|"  # Or single-label hostname (including localhost)
         r"\d{1,3}(\.\d{1,3}){3})"  # Or IPv4 address
         r"(:\d+)?"  # Optional port
         r"(/.*)?$"  # Optional path