* the target is requesting the head of a file it got a PutReplicaChunkRequest for.
*/
@Override
public void messageReceived(final GetBlobHeadRequest request, TransportChannel channel) throws Exception {
final BlobTransferStatus transferStatus = blobTransferTarget.getActiveTransfer(request.transferId);
assert transferStatus != null :
"Received GetBlobHeadRequest for transfer" + request.transferId.toString() + "but don't have an activeTransfer with that id";
final DiscoveryNode recipientNode = clusterService.state().getNodes().get(request.senderNodeId);
final File pendingFile = transferStatus.digestBlob().file();
final long bytesToSend = request.endPos;
blobTransferTarget.gotAGetBlobHeadRequest(request.transferId);
channel.sendResponse(TransportResponse.Empty.INSTANCE);