lib/api.js
function(params, cb) {
    var correlationId = _cbt.put(offFetchResponse(cb));
    var msg = envelope(offFetch.encode(params.fetchFromCoordinator ? 1 : 0)
                               .correlation(correlationId)
                               .client(_options.clientId)
                               .group(params.group)
                               .topic(params.topic)
                               .partition(params.partition)
                               .end());
    sendMsg(msg, correlationId, cb);
  }
function(params, cb) {
    var correlationId = _cbt.put(offFetchResponse(cb));
    var msg = envelope(offFetch.encode(params.fetchFromCoordinator ? 1 : 0)
                               .correlation(correlationId)
                               .client(_options.clientId)
                               .group(params.group)
                               .topic(params.topic)
                               .partition(params.partition)
                               .end());
    sendMsg(msg, correlationId, cb);
  }
function ( params , cb ) { var correlationId = _cbt . put ( offFetchResponse ( cb ) ) ; var msg = envelope ( offFetch . encode ( params . fetchFromCoordinator ? 1 : 0 ) . correlation ( correlationId ) . client ( _options . clientId ) . group ( params . group ) . topic ( params . topic ) . partition ( params . partition ) . end ( ) ) ; sendMsg ( msg , correlationId , cb ) ; }
write an offset request to kafka

params:
group: the consumer group id
topic: the topic to commit on
partition: the partition to commit on
write an offset request to kafka