private void doFill(T connection, Result result, String summaryClass, Execution execution) {
        try {
            fill(result, summaryClass, execution, connection);
        } catch (RuntimeException e) {
            result.hits().addError(ErrorMessage.createBackendCommunicationError("Error filling " + result + " from " + connection + ": " +
                                                                                Exceptions.toMessageString(e)));
        }
    }
Perform the search against the given connection. Return a result
containing an error or throw an exception on failures.
container-search/src/main/java/com/yahoo/search/cluster/ClusterSearcher.java