Optimize Memstore Flush for Hbase on S3(Object Store)

The current Memstore Flush Process is divided into 2 stages:

1. Flushcache: In this stage, a “.tmp” region file is written in S3/HDFS for the memstore;
2. Commit: In this stage, the “.tmp” file created in the stage 1 is renamed to final destination of HBase region file.

The above design(flush and commit) is OK for HDFS because “rename” is light opertion(only metadata operation). However, for storage like S3 or other object store, rename is “copy” and “delete” operation.

We can follow the same pattern from V2 of  “FileOutputCommitter” in MapReduce. That means, we can write hfile directly to the S3 destination directory without “copy” and “paste”. So that we can have less S3 operations and the HBase memstore flush is more efficient.