protected final void requestLogRoll(final WALActionsListener.RollRequestReason reason) {
    // If we have already requested a roll, don't do it again
    // And only set rollRequested to true when there is a registered listener
    if (!this.listeners.isEmpty() && rollRequested.compareAndSet(false, true)) {
      for (WALActionsListener i : this.listeners) {
        i.logRollRequested(reason);
      }
    }
  }
updates the sequence number of a specific store. depending on the flag: replaces current seq
number if the given seq id is bigger, or even if it is lower than existing one
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/AbstractFSWAL.java