WIP autoscaler agent

agent/nix_builder_autoscaler/providers/haproxy.py

@@ -0,0 +1,54 @@
+"""HAProxy runtime socket adapter — stub for Plan 02."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+class HAProxyError(Exception):
+    """Error communicating with HAProxy runtime socket."""
+
+
+@dataclass
+class SlotHealth:
+    """Health status for a single HAProxy server slot."""
+
+    status: str
+    scur: int
+    qcur: int
+
+
+class HAProxyRuntime:
+    """HAProxy runtime CLI adapter via Unix socket.
+
+    Full implementation in Plan 02.
+    """
+
+    def __init__(self, socket_path: str, backend: str, slot_prefix: str) -> None:
+        self._socket_path = socket_path
+        self._backend = backend
+        self._slot_prefix = slot_prefix
+
+    def set_slot_addr(self, slot_id: str, ip: str, port: int = 22) -> None:
+        """Update server address for a slot."""
+        raise NotImplementedError
+
+    def enable_slot(self, slot_id: str) -> None:
+        """Enable a server slot."""
+        raise NotImplementedError
+
+    def disable_slot(self, slot_id: str) -> None:
+        """Disable a server slot."""
+        raise NotImplementedError
+
+    def slot_is_up(self, slot_id: str) -> bool:
+        """Return True when HAProxy health status is UP for slot."""
+        raise NotImplementedError
+
+    def slot_session_count(self, slot_id: str) -> int:
+        """Return current active session count for slot."""
+        raise NotImplementedError
+
+    def read_slot_health(self) -> dict[str, SlotHealth]:
+        """Return full stats snapshot for all slots."""
+        raise NotImplementedError