cluster-common/src/main/java/com/streamsets/pipeline/cluster/Consumer.java
public void commit(String offset) {
    batchCommitted = true;
    LOG.trace("Last committed offset '{}', attempting to commit '{}'", lastCommittedOffset, offset);
    Utils.checkState(null != lastCommittedOffset, "Last committed offset cannot be null");
    controlChannel.consumerCommit(offset);
    lastCommittedOffset = offset;
  }
public void commit(String offset) {
    batchCommitted = true;
    LOG.trace("Last committed offset '{}', attempting to commit '{}'", lastCommittedOffset, offset);
    Utils.checkState(null != lastCommittedOffset, "Last committed offset cannot be null");
    controlChannel.consumerCommit(offset);
    lastCommittedOffset = offset;
  }
Commit the offset. Required after take has returned a non-null value.