diff --git a/demo_test/vendor/github.com/Shopify/sarama/offset_manager.go b/demo_test/vendor/github.com/Shopify/sarama/offset_manager.go
new file mode 100644
index 0000000..1940872
--- /dev/null
+++ b/demo_test/vendor/github.com/Shopify/sarama/offset_manager.go
@@ -0,0 +1,584 @@
+package sarama
+
+import (
+	"sync"
+	"time"
+)
+
+// Offset Manager
+
+// OffsetManager uses Kafka to store and fetch consumed partition offsets.
+type OffsetManager interface {
+	// ManagePartition creates a PartitionOffsetManager on the given topic/partition.
+	// It will return an error if this OffsetManager is already managing the given
+	// topic/partition.
+	ManagePartition(topic string, partition int32) (PartitionOffsetManager, error)
+
+	// Close stops the OffsetManager from managing offsets. It is required to call
+	// this function before an OffsetManager object passes out of scope, as it
+	// will otherwise leak memory. You must call this after all the
+	// PartitionOffsetManagers are closed.
+	Close() error
+}
+
+type offsetManager struct {
+	client Client
+	conf   *Config
+	group  string
+	ticker *time.Ticker
+
+	memberID   string
+	generation int32
+
+	broker     *Broker
+	brokerLock sync.RWMutex
+
+	poms     map[string]map[int32]*partitionOffsetManager
+	pomsLock sync.RWMutex
+
+	closeOnce sync.Once
+	closing   chan none
+	closed    chan none
+}
+
+// NewOffsetManagerFromClient creates a new OffsetManager from the given client.
+// It is still necessary to call Close() on the underlying client when finished with the partition manager.
+func NewOffsetManagerFromClient(group string, client Client) (OffsetManager, error) {
+	return newOffsetManagerFromClient(group, "", GroupGenerationUndefined, client)
+}
+
+func newOffsetManagerFromClient(group, memberID string, generation int32, client Client) (*offsetManager, error) {
+	// Check that we are not dealing with a closed Client before processing any other arguments
+	if client.Closed() {
+		return nil, ErrClosedClient
+	}
+
+	conf := client.Config()
+	om := &offsetManager{
+		client: client,
+		conf:   conf,
+		group:  group,
+		ticker: time.NewTicker(conf.Consumer.Offsets.AutoCommit.Interval),
+		poms:   make(map[string]map[int32]*partitionOffsetManager),
+
+		memberID:   memberID,
+		generation: generation,
+
+		closing: make(chan none),
+		closed:  make(chan none),
+	}
+	go withRecover(om.mainLoop)
+
+	return om, nil
+}
+
+func (om *offsetManager) ManagePartition(topic string, partition int32) (PartitionOffsetManager, error) {
+	pom, err := om.newPartitionOffsetManager(topic, partition)
+	if err != nil {
+		return nil, err
+	}
+
+	om.pomsLock.Lock()
+	defer om.pomsLock.Unlock()
+
+	topicManagers := om.poms[topic]
+	if topicManagers == nil {
+		topicManagers = make(map[int32]*partitionOffsetManager)
+		om.poms[topic] = topicManagers
+	}
+
+	if topicManagers[partition] != nil {
+		return nil, ConfigurationError("That topic/partition is already being managed")
+	}
+
+	topicManagers[partition] = pom
+	return pom, nil
+}
+
+func (om *offsetManager) Close() error {
+	om.closeOnce.Do(func() {
+		// exit the mainLoop
+		close(om.closing)
+		<-om.closed
+
+		// mark all POMs as closed
+		om.asyncClosePOMs()
+
+		// flush one last time
+		for attempt := 0; attempt <= om.conf.Consumer.Offsets.Retry.Max; attempt++ {
+			om.flushToBroker()
+			if om.releasePOMs(false) == 0 {
+				break
+			}
+		}
+
+		om.releasePOMs(true)
+		om.brokerLock.Lock()
+		om.broker = nil
+		om.brokerLock.Unlock()
+	})
+	return nil
+}
+
+func (om *offsetManager) computeBackoff(retries int) time.Duration {
+	if om.conf.Metadata.Retry.BackoffFunc != nil {
+		return om.conf.Metadata.Retry.BackoffFunc(retries, om.conf.Metadata.Retry.Max)
+	} else {
+		return om.conf.Metadata.Retry.Backoff
+	}
+}
+
+func (om *offsetManager) fetchInitialOffset(topic string, partition int32, retries int) (int64, string, error) {
+	broker, err := om.coordinator()
+	if err != nil {
+		if retries <= 0 {
+			return 0, "", err
+		}
+		return om.fetchInitialOffset(topic, partition, retries-1)
+	}
+
+	req := new(OffsetFetchRequest)
+	req.Version = 1
+	req.ConsumerGroup = om.group
+	req.AddPartition(topic, partition)
+
+	resp, err := broker.FetchOffset(req)
+	if err != nil {
+		if retries <= 0 {
+			return 0, "", err
+		}
+		om.releaseCoordinator(broker)
+		return om.fetchInitialOffset(topic, partition, retries-1)
+	}
+
+	block := resp.GetBlock(topic, partition)
+	if block == nil {
+		return 0, "", ErrIncompleteResponse
+	}
+
+	switch block.Err {
+	case ErrNoError:
+		return block.Offset, block.Metadata, nil
+	case ErrNotCoordinatorForConsumer:
+		if retries <= 0 {
+			return 0, "", block.Err
+		}
+		om.releaseCoordinator(broker)
+		return om.fetchInitialOffset(topic, partition, retries-1)
+	case ErrOffsetsLoadInProgress:
+		if retries <= 0 {
+			return 0, "", block.Err
+		}
+		backoff := om.computeBackoff(retries)
+		select {
+		case <-om.closing:
+			return 0, "", block.Err
+		case <-time.After(backoff):
+		}
+		return om.fetchInitialOffset(topic, partition, retries-1)
+	default:
+		return 0, "", block.Err
+	}
+}
+
+func (om *offsetManager) coordinator() (*Broker, error) {
+	om.brokerLock.RLock()
+	broker := om.broker
+	om.brokerLock.RUnlock()
+
+	if broker != nil {
+		return broker, nil
+	}
+
+	om.brokerLock.Lock()
+	defer om.brokerLock.Unlock()
+
+	if broker := om.broker; broker != nil {
+		return broker, nil
+	}
+
+	if err := om.client.RefreshCoordinator(om.group); err != nil {
+		return nil, err
+	}
+
+	broker, err := om.client.Coordinator(om.group)
+	if err != nil {
+		return nil, err
+	}
+
+	om.broker = broker
+	return broker, nil
+}
+
+func (om *offsetManager) releaseCoordinator(b *Broker) {
+	om.brokerLock.Lock()
+	if om.broker == b {
+		om.broker = nil
+	}
+	om.brokerLock.Unlock()
+}
+
+func (om *offsetManager) mainLoop() {
+	defer om.ticker.Stop()
+	defer close(om.closed)
+
+	for {
+		select {
+		case <-om.ticker.C:
+			om.flushToBroker()
+			om.releasePOMs(false)
+		case <-om.closing:
+			return
+		}
+	}
+}
+
+// flushToBroker is ignored if auto-commit offsets is disabled
+func (om *offsetManager) flushToBroker() {
+	if !om.conf.Consumer.Offsets.AutoCommit.Enable {
+		return
+	}
+
+	req := om.constructRequest()
+	if req == nil {
+		return
+	}
+
+	broker, err := om.coordinator()
+	if err != nil {
+		om.handleError(err)
+		return
+	}
+
+	resp, err := broker.CommitOffset(req)
+	if err != nil {
+		om.handleError(err)
+		om.releaseCoordinator(broker)
+		_ = broker.Close()
+		return
+	}
+
+	om.handleResponse(broker, req, resp)
+}
+
+func (om *offsetManager) constructRequest() *OffsetCommitRequest {
+	var r *OffsetCommitRequest
+	var perPartitionTimestamp int64
+	if om.conf.Consumer.Offsets.Retention == 0 {
+		perPartitionTimestamp = ReceiveTime
+		r = &OffsetCommitRequest{
+			Version:                 1,
+			ConsumerGroup:           om.group,
+			ConsumerID:              om.memberID,
+			ConsumerGroupGeneration: om.generation,
+		}
+	} else {
+		r = &OffsetCommitRequest{
+			Version:                 2,
+			RetentionTime:           int64(om.conf.Consumer.Offsets.Retention / time.Millisecond),
+			ConsumerGroup:           om.group,
+			ConsumerID:              om.memberID,
+			ConsumerGroupGeneration: om.generation,
+		}
+	}
+
+	om.pomsLock.RLock()
+	defer om.pomsLock.RUnlock()
+
+	for _, topicManagers := range om.poms {
+		for _, pom := range topicManagers {
+			pom.lock.Lock()
+			if pom.dirty {
+				r.AddBlock(pom.topic, pom.partition, pom.offset, perPartitionTimestamp, pom.metadata)
+			}
+			pom.lock.Unlock()
+		}
+	}
+
+	if len(r.blocks) > 0 {
+		return r
+	}
+
+	return nil
+}
+
+func (om *offsetManager) handleResponse(broker *Broker, req *OffsetCommitRequest, resp *OffsetCommitResponse) {
+	om.pomsLock.RLock()
+	defer om.pomsLock.RUnlock()
+
+	for _, topicManagers := range om.poms {
+		for _, pom := range topicManagers {
+			if req.blocks[pom.topic] == nil || req.blocks[pom.topic][pom.partition] == nil {
+				continue
+			}
+
+			var err KError
+			var ok bool
+
+			if resp.Errors[pom.topic] == nil {
+				pom.handleError(ErrIncompleteResponse)
+				continue
+			}
+			if err, ok = resp.Errors[pom.topic][pom.partition]; !ok {
+				pom.handleError(ErrIncompleteResponse)
+				continue
+			}
+
+			switch err {
+			case ErrNoError:
+				block := req.blocks[pom.topic][pom.partition]
+				pom.updateCommitted(block.offset, block.metadata)
+			case ErrNotLeaderForPartition, ErrLeaderNotAvailable,
+				ErrConsumerCoordinatorNotAvailable, ErrNotCoordinatorForConsumer:
+				// not a critical error, we just need to redispatch
+				om.releaseCoordinator(broker)
+			case ErrOffsetMetadataTooLarge, ErrInvalidCommitOffsetSize:
+				// nothing we can do about this, just tell the user and carry on
+				pom.handleError(err)
+			case ErrOffsetsLoadInProgress:
+				// nothing wrong but we didn't commit, we'll get it next time round
+			case ErrUnknownTopicOrPartition:
+				// let the user know *and* try redispatching - if topic-auto-create is
+				// enabled, redispatching should trigger a metadata req and create the
+				// topic; if not then re-dispatching won't help, but we've let the user
+				// know and it shouldn't hurt either (see https://github.com/Shopify/sarama/issues/706)
+				fallthrough
+			default:
+				// dunno, tell the user and try redispatching
+				pom.handleError(err)
+				om.releaseCoordinator(broker)
+			}
+		}
+	}
+}
+
+func (om *offsetManager) handleError(err error) {
+	om.pomsLock.RLock()
+	defer om.pomsLock.RUnlock()
+
+	for _, topicManagers := range om.poms {
+		for _, pom := range topicManagers {
+			pom.handleError(err)
+		}
+	}
+}
+
+func (om *offsetManager) asyncClosePOMs() {
+	om.pomsLock.RLock()
+	defer om.pomsLock.RUnlock()
+
+	for _, topicManagers := range om.poms {
+		for _, pom := range topicManagers {
+			pom.AsyncClose()
+		}
+	}
+}
+
+// Releases/removes closed POMs once they are clean (or when forced)
+func (om *offsetManager) releasePOMs(force bool) (remaining int) {
+	om.pomsLock.Lock()
+	defer om.pomsLock.Unlock()
+
+	for topic, topicManagers := range om.poms {
+		for partition, pom := range topicManagers {
+			pom.lock.Lock()
+			releaseDue := pom.done && (force || !pom.dirty)
+			pom.lock.Unlock()
+
+			if releaseDue {
+				pom.release()
+
+				delete(om.poms[topic], partition)
+				if len(om.poms[topic]) == 0 {
+					delete(om.poms, topic)
+				}
+			}
+		}
+		remaining += len(om.poms[topic])
+	}
+	return
+}
+
+func (om *offsetManager) findPOM(topic string, partition int32) *partitionOffsetManager {
+	om.pomsLock.RLock()
+	defer om.pomsLock.RUnlock()
+
+	if partitions, ok := om.poms[topic]; ok {
+		if pom, ok := partitions[partition]; ok {
+			return pom
+		}
+	}
+	return nil
+}
+
+// Partition Offset Manager
+
+// PartitionOffsetManager uses Kafka to store and fetch consumed partition offsets. You MUST call Close()
+// on a partition offset manager to avoid leaks, it will not be garbage-collected automatically when it passes
+// out of scope.
+type PartitionOffsetManager interface {
+	// NextOffset returns the next offset that should be consumed for the managed
+	// partition, accompanied by metadata which can be used to reconstruct the state
+	// of the partition consumer when it resumes. NextOffset() will return
+	// `config.Consumer.Offsets.Initial` and an empty metadata string if no offset
+	// was committed for this partition yet.
+	NextOffset() (int64, string)
+
+	// MarkOffset marks the provided offset, alongside a metadata string
+	// that represents the state of the partition consumer at that point in time. The
+	// metadata string can be used by another consumer to restore that state, so it
+	// can resume consumption.
+	//
+	// To follow upstream conventions, you are expected to mark the offset of the
+	// next message to read, not the last message read. Thus, when calling `MarkOffset`
+	// you should typically add one to the offset of the last consumed message.
+	//
+	// Note: calling MarkOffset does not necessarily commit the offset to the backend
+	// store immediately for efficiency reasons, and it may never be committed if
+	// your application crashes. This means that you may end up processing the same
+	// message twice, and your processing should ideally be idempotent.
+	MarkOffset(offset int64, metadata string)
+
+	// ResetOffset resets to the provided offset, alongside a metadata string that
+	// represents the state of the partition consumer at that point in time. Reset
+	// acts as a counterpart to MarkOffset, the difference being that it allows to
+	// reset an offset to an earlier or smaller value, where MarkOffset only
+	// allows incrementing the offset. cf MarkOffset for more details.
+	ResetOffset(offset int64, metadata string)
+
+	// Errors returns a read channel of errors that occur during offset management, if
+	// enabled. By default, errors are logged and not returned over this channel. If
+	// you want to implement any custom error handling, set your config's
+	// Consumer.Return.Errors setting to true, and read from this channel.
+	Errors() <-chan *ConsumerError
+
+	// AsyncClose initiates a shutdown of the PartitionOffsetManager. This method will
+	// return immediately, after which you should wait until the 'errors' channel has
+	// been drained and closed. It is required to call this function, or Close before
+	// a consumer object passes out of scope, as it will otherwise leak memory. You
+	// must call this before calling Close on the underlying client.
+	AsyncClose()
+
+	// Close stops the PartitionOffsetManager from managing offsets. It is required to
+	// call this function (or AsyncClose) before a PartitionOffsetManager object
+	// passes out of scope, as it will otherwise leak memory. You must call this
+	// before calling Close on the underlying client.
+	Close() error
+}
+
+type partitionOffsetManager struct {
+	parent    *offsetManager
+	topic     string
+	partition int32
+
+	lock     sync.Mutex
+	offset   int64
+	metadata string
+	dirty    bool
+	done     bool
+
+	releaseOnce sync.Once
+	errors      chan *ConsumerError
+}
+
+func (om *offsetManager) newPartitionOffsetManager(topic string, partition int32) (*partitionOffsetManager, error) {
+	offset, metadata, err := om.fetchInitialOffset(topic, partition, om.conf.Metadata.Retry.Max)
+	if err != nil {
+		return nil, err
+	}
+
+	return &partitionOffsetManager{
+		parent:    om,
+		topic:     topic,
+		partition: partition,
+		errors:    make(chan *ConsumerError, om.conf.ChannelBufferSize),
+		offset:    offset,
+		metadata:  metadata,
+	}, nil
+}
+
+func (pom *partitionOffsetManager) Errors() <-chan *ConsumerError {
+	return pom.errors
+}
+
+func (pom *partitionOffsetManager) MarkOffset(offset int64, metadata string) {
+	pom.lock.Lock()
+	defer pom.lock.Unlock()
+
+	if offset > pom.offset {
+		pom.offset = offset
+		pom.metadata = metadata
+		pom.dirty = true
+	}
+}
+
+func (pom *partitionOffsetManager) ResetOffset(offset int64, metadata string) {
+	pom.lock.Lock()
+	defer pom.lock.Unlock()
+
+	if offset <= pom.offset {
+		pom.offset = offset
+		pom.metadata = metadata
+		pom.dirty = true
+	}
+}
+
+func (pom *partitionOffsetManager) updateCommitted(offset int64, metadata string) {
+	pom.lock.Lock()
+	defer pom.lock.Unlock()
+
+	if pom.offset == offset && pom.metadata == metadata {
+		pom.dirty = false
+	}
+}
+
+func (pom *partitionOffsetManager) NextOffset() (int64, string) {
+	pom.lock.Lock()
+	defer pom.lock.Unlock()
+
+	if pom.offset >= 0 {
+		return pom.offset, pom.metadata
+	}
+
+	return pom.parent.conf.Consumer.Offsets.Initial, ""
+}
+
+func (pom *partitionOffsetManager) AsyncClose() {
+	pom.lock.Lock()
+	pom.done = true
+	pom.lock.Unlock()
+}
+
+func (pom *partitionOffsetManager) Close() error {
+	pom.AsyncClose()
+
+	var errors ConsumerErrors
+	for err := range pom.errors {
+		errors = append(errors, err)
+	}
+
+	if len(errors) > 0 {
+		return errors
+	}
+	return nil
+}
+
+func (pom *partitionOffsetManager) handleError(err error) {
+	cErr := &ConsumerError{
+		Topic:     pom.topic,
+		Partition: pom.partition,
+		Err:       err,
+	}
+
+	if pom.parent.conf.Consumer.Return.Errors {
+		pom.errors <- cErr
+	} else {
+		Logger.Println(cErr)
+	}
+}
+
+func (pom *partitionOffsetManager) release() {
+	pom.releaseOnce.Do(func() {
+		close(pom.errors)
+	})
+}