code: private Completable initFromBeginningToNow() {
      return initWithCallback(new Action1<PartitionAndSeqno>() {
        @Override
        public void call(PartitionAndSeqno partitionAndSeqno) {
          short partition = partitionAndSeqno.partition();
          long seqno = partitionAndSeqno.seqno();
          PartitionState partitionState = sessionState().get(partition);
          partitionState.setEndSeqno(seqno);
          sessionState().set(partition, partitionState);
        }
      });
    }
docs: Initializes the session state from beginning to now.