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This article mainly shows you the "sample discovery of hbase cache", which is easy to understand and well organized. I hope it can help you solve your doubts. Let the editor lead you to study and learn the article "sample discovery of hbase cache".

The memory of Regionserver on HBase is divided into two parts, one as Memstore, which is mainly used for writing, and the other as BlockCache, which is mainly used for reading.

The write request will be written to Memstore,Regionserver first and each region will be provided with a Memstore. When the Memstore is full of 64MB, it will start flush to flush to disk. When the total size of the Memstore exceeds the limit (heapsize * hbase.regionserver.global.memstore.upperLimit * 0.9), the flush process is forcibly started, starting from the largest Memstore until the flush is below the limit.

The read request will first check the data in Memstore, and if it cannot be found, it will be checked in BlockCache. If it cannot be found, it will be read on disk, and the read result will be put into BlockCache. Because BlockCache uses the LRU strategy, when the BlockCache reaches the upper limit (heapsize * hfile.block.cache.size * 0.85), the phase-out mechanism is activated to phase out the oldest batch of data.

There is a BlockCache and N Memstore on a Regionserver, and the sum of their sizes cannot be greater than or equal to heapsize * 0.8, otherwise the HBase will not start normally.

By default, BlockCache is 0.2 and Memstore is 0.4. In an application scenario that focuses on read response time, you can set BlockCache larger and Memstore smaller to increase the cache hit rate.

The above is all the content of the article "sample Discovery of hbase caching". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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