同花顺面试（部分）

我不是女神ヾ 2023-09-25 15:43 103阅读 0赞

又没录上，只能凭零星记忆来记录了

*  知识图谱有了解吗，知道用在你们系统哪个环节吗
 *  tomcat内存设置的多大。32位系统的话有限制吗？复盘：后面一想，可能是说32位系统地址寻址空间有限，内存最多4G
 *  gprc你们用的序列化方式？A：protobuf。Q：网络通信协议是HTTP还是TCP。复盘：HTTP2
 *  如何处理kafka的重复消息
 *  elasticSearch集群搭建的情况。index是定时刷新还是实时刷新的？  
    我参考了一些文档1 2 ，包括elastic的官网3：

> Sitting between Elasticsearch and the disk is the filesystem cache. Documents in the in-memory indexing buffer (Figure 1) are written to a new segment (Figure 2). The new segment is written to the filesystem cache first (which is cheap) and only later is it flushed to disk(which is expensive). However, after a file is in the cache, it can be opened and read just like any other file.

![在这里插入图片描述][00fcca521a384f84b2e835d0ffa72335.png]

> In Elasticsearch, this process of writing and opening a new segment is called a refresh … You can control refreshes through the following means: … Waiting for the refresh interval …

> By default, Elasticsearch periodically refreshes indices every second … This is why we say that Elasticsearch has near real-time search

给出了自己的简单概括（这个也可以回答2021年面试乐言时为什么es是近实时的提问）：  
ES写入数据是先把数据写进内存，再写入 filesystem cache，最后再写入硬盘。在第二步（写入filesystem cache形成新的segment，这一步也被称为***refresh***）后，新数据就可以被搜索到了。refresh默认一秒执行一次（其实官网原文还有个条件，就是过去30秒有收到查询请求的index）。

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1.  [ES近实时刷新与refresh\_interval参数设置相关问题][ES_refresh_interval] ↩︎
2.  [elasticsearch的数据写入流程及优化][elasticsearch] ↩︎
3.  [elastic : Near real-time search][elastic _ Near real-time search] ↩︎

[00fcca521a384f84b2e835d0ffa72335.png]: https://img-blog.csdnimg.cn/00fcca521a384f84b2e835d0ffa72335.png
[ES_refresh_interval]: https://blog.csdn.net/Tony_zt/article/details/122383372
[elasticsearch]: https://www.cnblogs.com/zhangan/p/11231990.html
[elastic _ Near real-time search]: https://www.elastic.co/guide/en/elasticsearch/reference/8.6/near-real-time.html#img-pre-refresh