WIP autoscaler agent

agent/nix_builder_autoscaler/providers/clock.py

@@ -0,0 +1,39 @@
+"""Injectable clock abstraction for testability."""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime, timedelta
+from typing import Protocol
+
+
+class Clock(Protocol):
+    """Clock protocol — provides current UTC time."""
+
+    def now(self) -> datetime: ...
+
+
+class SystemClock:
+    """Real wall-clock implementation."""
+
+    def now(self) -> datetime:
+        """Return the current UTC time."""
+        return datetime.now(UTC)
+
+
+class FakeClock:
+    """Deterministic clock for tests."""
+
+    def __init__(self, start: datetime | None = None) -> None:
+        self._now = start or datetime(2026, 1, 1, tzinfo=UTC)
+
+    def now(self) -> datetime:
+        """Return the fixed current time."""
+        return self._now
+
+    def advance(self, seconds: float) -> None:
+        """Advance the clock by the given number of seconds."""
+        self._now += timedelta(seconds=seconds)
+
+    def set(self, dt: datetime) -> None:
+        """Set the clock to an exact time."""
+        self._now = dt

agent/nix_builder_autoscaler/providers/haproxy.py

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+"""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