@Override
  protected int getStateId(RecoverStandbyState state) {
    return state.getNumber();
  }
The procedure for replaying all the remote wals for transitting a sync replication peer from
STANDBY to DOWNGRADE_ACTIVE.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/replication/RecoverStandbyProcedure.java