presto-main/src/main/java/io/prestosql/server/remotetask/TaskInfoFetcher.java/TaskInfoFetcher/scheduleUpdate
class TaskInfoFetcher:    private synchronized void scheduleUpdate()
    {
        scheduledFuture = updateScheduledExecutor.scheduleWithFixedDelay(() -> {
            synchronized (this) {
                // if the previous request still running, don't schedule a new request
                if (future != null && !future.isDone()) {
                    return;
                }
            }
            if (nanosSince(lastUpdateNanos.get()).toMillis() >= updateIntervalMillis) {
                sendNextRequest();
            }
        }, 0, 100, MILLISECONDS);
    }