What happens when a ScheduledExecutorService task throws?

scheduleAtFixedRate and scheduleWithFixedDelay stop rescheduling if the task throws. The ScheduledFuture completes exceptionally, and because nobody holds it, the failure is invisible. The symptom is a heartbeat, a cache refresh or a cleanup job that "stopped working last Tuesday".

The fix is to make the task incapable of throwing:

scheduler.scheduleWithFixedDelay(() -> {
    try {
        refresh();
    } catch (Throwable t) {          // Throwable: an Error kills the schedule just as dead
        log.error("refresh failed", t);
    }
}, 0, 1, MINUTES);

While you are there: scheduleAtFixedRate measures from start to start, so if a run overruns the period the next one begins immediately and they can pile up. scheduleWithFixedDelay measures from end to start and cannot.