@Override
  public void cleanup(Exception e) {
    LOG.info("Aborting all online FLUSH snapshot subprocedure task threads for '"
      + snapshot.getName() + "' due to error", e);
    try {
      taskManager.cancelTasks();
    } catch (InterruptedException e1) {
      Thread.currentThread().interrupt();
    }
  }
Cancel threads if they haven't finished.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/snapshot/FlushSnapshotSubprocedure.java