@Override
    public boolean offer(final E e, final long timeout, final TimeUnit unit) throws InterruptedException {
        return memoryLimiter.acquire(e, timeout, unit) && super.offer(e, timeout, unit);
    }
get the current remain memory.

@return the current remain memory
shenyu-common/src/main/java/org/apache/shenyu/common/concurrent/MemoryLimitedLinkedBlockingQueue.java