Drain Marker Policy • AI Agent SDK

DrainMarkerPolicy: Pure predicate deciding whether an external drain marker is actionable.

DrainMarkerPolicy

Defined in the protocols module.

Pure predicate deciding whether an external drain marker is actionable.

A drain marker is a small JSON object written by an operator / deploy step (via `praisonai gateway drain`) into a well-known path. A background watcher in the wrapper reads it and asks this policy whether the running gateway should react. The decision is intentionally side-effect free so it is provable in isolation without a live gateway or filesystem.

A marker is honoured only when it requests a drain for the current instantiation:

• a missing marker (`None`) is never a drain request;
• a marker carrying no `epoch` is treated as foreign and ignored, so a
• hand-rolled or legacy file cannot wedge a process;
• a marker whose `epoch differs from current_epoch` is stale — it
• survived a reboot/restart on a durable volume — and is ignored;
• a current-epoch marker is honoured (subject to an optional
• already-handled de-duplication via `last_handled_epoch`).

Example::

policy = DrainMarkerPolicy()
if policy.drain_requested(read_marker(), current_epoch(), monotonic()):
    await gateway.stop(drain_timeout=cfg.gateway.drain_timeout)

Methods

Source