* If an error occurs during communication with the Riak server.
* @throws RiakResponseRuntimeException
* If the Riak server does not return a valid JSON array.
*/
public MapReduceResponse mapReduce(String job, RequestMeta meta) {
HttpResponse r = helper.mapReduce(job, meta);
try {
return getMapReduceResponse(r);
} catch (JSONException e) {
helper.toss(new RiakResponseRuntimeException(r, e));
return null;