oneShotJitteredNextCronRunMs function

int? oneShotJitteredNextCronRunMs(String cron, int fromMs, String taskId, [ CronJitterConfig cfg = kDefaultCronJitterConfig, ])

Same as nextCronRunMs, minus a deterministic per-task lead time when the fire time lands on a minute boundary matching CronJitterConfig.oneShotMinuteMod.

One-shot tasks are user-pinned so delaying them breaks the contract, but firing slightly early is invisible and spreads the inference spike.

Implementation

int? oneShotJitteredNextCronRunMs(
  String cron,
  int fromMs,
  String taskId, [
  CronJitterConfig cfg = kDefaultCronJitterConfig,
]) {
  final t1 = nextCronRunMs(cron, fromMs);
  if (t1 == null) return null;
  final dt = DateTime.fromMillisecondsSinceEpoch(t1);
  if (dt.minute % cfg.oneShotMinuteMod != 0) return t1;
  final lead =
      cfg.oneShotFloorMs +
      _jitterFrac(taskId) * (cfg.oneShotMaxMs - cfg.oneShotFloorMs);
  return max(t1 - lead.round(), fromMs);
}