private void initializeReplicationMarkerChore() {
    boolean replicationMarkerEnabled =
      conf.getBoolean(REPLICATION_MARKER_ENABLED_KEY, REPLICATION_MARKER_ENABLED_DEFAULT);
    // If replication or replication marker is not enabled then return immediately.
    if (replicationMarkerEnabled) {
      int period = conf.getInt(REPLICATION_MARKER_CHORE_DURATION_KEY,
        REPLICATION_MARKER_CHORE_DURATION_DEFAULT);
      replicationMarkerChore = new ReplicationMarkerChore(this, this, period, conf);
    }
  }
Returns True if the cluster is up.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java