@SuppressWarnings("deprecation")
  @Override
  public CoprocessorRpcChannel coprocessorService() {
    return new SyncCoprocessorRpcChannelOverAsync(
      new MasterCoprocessorRpcChannelImpl(admin.<Message> newMasterCaller()));
  }
The {@link Admin} implementation which is based on an {@link AsyncAdmin}.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AdminOverAsyncAdmin.java