@Override
  protected void createStoreFlusher(Configuration conf, HStore store) throws IOException {
    // When using MOB, we use DefaultMobStoreFlusher always
    // Just use the compactor and compaction policy as that in DefaultStoreEngine. We can have MOB
    // specific compactor and policy when that is implemented.
    storeFlusher = new DefaultMobStoreFlusher(conf, store);
  }
MobStoreEngine creates the mob specific compactor, and store flusher.
hbase-server/src/main/java/org/apache/hadoop/hbase/mob/MobStoreEngine.java