public boolean walRollFinished() {
    // TODO add a status field of roll in RollController
    return wals.values().stream()
      .noneMatch(rc -> rc.needsRoll(EnvironmentEdgeManager.currentTime())) && isWaiting();
  }
Returns true if all WAL roll finished
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractWALRoller.java