@Override
    public void run() {
      inMemoryCompaction();
    }
The in-memory-flusher thread performs the flush asynchronously. There is at most one thread per
memstore instance. It takes the updatesLock exclusively, pushes active into the pipeline,
releases updatesLock and compacts the pipeline.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CompactingMemStore.java