The drainer's polling loop has been gated on WORKER_ENABLED, which
couples it to the legacy ZodWorker role. To split the drainer onto a
dedicated worker service in cloud (and keep all other replicas as
producer-only), introduce its own switch.
Semantics:
- Unset → inherits MOLLIFIER_ENABLED.
Single-container self-hosters with MOLLIFIER_ENABLED=1 get the
drainer for free, no second flag to remember.
- Explicit MOLLIFIER_DRAINER_ENABLED=0 → drainer off on this replica.
Cloud sets this everywhere except the dedicated drainer service.
- Explicit MOLLIFIER_DRAINER_ENABLED=1 → drainer on, subject to
MOLLIFIER_ENABLED still being the master kill switch (a drainer
can't construct without the gate-side buffer singleton).
The bootstrap in mollifierDrainerWorker.server.ts now gates on the new
flag instead of WORKER_ENABLED, so the drainer's lifecycle is no longer
coupled to the legacy worker role.
Dan Sutton
ad90fe38ac