private boolean isMergeable(final MasterProcedureEnv env, final RegionState rs)
    throws IOException {
    GetRegionInfoResponse response =
      AssignmentManagerUtil.getRegionInfoResponse(env, rs.getServerName(), rs.getRegion());
    return response.hasMergeable() && response.getMergeable();
  }
Prepare merge and do some check
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/MergeTableRegionsProcedure.java