private int validAndGetMemCacheSize(TopicMetadata topicMetadata) {
        int memCacheSize = topicMetadata.getMemCacheMsgSize();
        if (memCacheSize < topicMetadata.getMinMemCacheSize()) {
            logger.info(new StringBuilder(512)
                    .append("[Data Store] ").append(getTopic())
                    .append(" writeCacheMaxSize changed, from ")
                    .append(memCacheSize).append(" to ")
                    .append(topicMetadata.getMinMemCacheSize()).toString());
            memCacheSize = topicMetadata.getMinMemCacheSize();
        }
        return memCacheSize;
    }
Get the data total size
If memory cache is enabled, the data in the cache is counted first,
and then the data in the file is counted

@return  the current data total size
inlong-tubemq/tubemq-server/src/main/java/org/apache/inlong/tubemq/server/broker/msgstore/MessageStore.java