public static WALKeyImpl writeFlushMarker(WAL wal, NavigableMap<byte[], Integer> replicationScope,
    RegionInfo hri, final FlushDescriptor f, boolean sync, MultiVersionConcurrencyControl mvcc,
    RegionReplicationSink sink) throws IOException {
    WALKeyImpl walKey = doFullMarkerAppendTransaction(wal, replicationScope, hri,
      WALEdit.createFlushWALEdit(hri, f), mvcc, null, sync, sink);
    if (LOG.isTraceEnabled()) {
      LOG.trace("Appended flush marker " + TextFormat.shortDebugString(f));
    }
    return walKey;
  }
Write a flush marker indicating a start / abort or a complete of a region flush
<p/>
This write is for internal use only. Not for external client consumption.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALUtil.java