private void replayWALFlushCannotFlushMarker(FlushDescriptor flush, long replaySeqId) {
    synchronized (writestate) {
      if (this.lastReplayedOpenRegionSeqId > replaySeqId) {
        LOG.warn(getRegionInfo().getEncodedName() + " : " + "Skipping replaying flush event :"
          + TextFormat.shortDebugString(flush) + " because its sequence id " + replaySeqId
          + " is smaller than this regions " + "lastReplayedOpenRegionSeqId of "
          + lastReplayedOpenRegionSeqId);
        return;
      }

      // If we were waiting for observing a flush or region opening event for not showing partial
      // data after a secondary region crash, we can allow reads now. This event means that the
      // primary was not able to flush because memstore is empty when we requested flush. By the
      // time we observe this, we are guaranteed to have up to date seqId with our previous
      // assignment.
      this.setReadsEnabled(true);
    }
  }
Drops the memstore contents after replaying a flush descriptor or region open event replay if
the memstore edits have seqNums smaller than the given seq id
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java