private void triggerConnectionError(String datacenter, SQLException connectionError) {
      try {
        DataSource dataSource = dataSources.get(datacenter);
        reset(dataSource);
        when(dataSource.getConnection()).thenThrow(connectionError);
      } catch (SQLException e) {
        throw new RuntimeException(e);
      }
    }
@param callable an async call, where the {@link Future} is expected to be completed with an exception.
@param errorCode the expected {@link RestServiceErrorCode}.
ambry-named-mysql/src/test/java/com/github/ambry/named/MySqlNamedBlobDbTest.java