private void flush() {
        long currentTime = System.currentTimeMillis();
        if (currentTime - lastSendTime > l1FlushPeriod) {
            mergeDataCache.read().forEach(
                data -> {
                    nextWorker.in(data);
                }
            );
            lastSendTime = currentTime;
        }
    }
Dequeue consuming. According to {@link IConsumer#consume(List)}, this is a serial operation for every work
instance.

@param metricsList from the queue.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/worker/MetricsAggregateWorker.java