@Override
  public ModifyTableResponse modifyTable(RpcController controller, ModifyTableRequest req)
    throws ServiceException {
    try {
      long procId = server.modifyTable(ProtobufUtil.toTableName(req.getTableName()),
        ProtobufUtil.toTableDescriptor(req.getTableSchema()), req.getNonceGroup(), req.getNonce(),
        req.getReopenRegions());
      return ModifyTableResponse.newBuilder().setProcId(procId).build();
    } catch (IOException ioe) {
      throw new ServiceException(ioe);
    }
  }
Checks if the specified snapshot is done.
@return true if the snapshot is in file system ready to use, false if the snapshot is in the
        process of completing
@throws ServiceException wrapping UnknownSnapshotException if invalid snapshot, or a wrapped
                         HBaseSnapshotException with progress failure reason.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java