piping proposed transaction timestimp through to server and back for TAPIR

store/tapirstore/server.cc

@@ -75,14 +75,20 @@ Server::ExecConsensusUpcall(const string &str1, string &str2)
     Request request;
     Reply reply;
     int status;
+    Timestamp proposed;
     
     request.ParseFromString(str1);
 
     switch (request.op()) {
     case tapirstore::proto::Request::PREPARE:
         status = store->Prepare(request.txnid(),
-                                Transaction(request.prepare().txn()));
+                                Transaction(request.prepare().txn()),
+                                Timestamp(request.prepare().timestamp()),
+                                proposed);
         reply.set_status(status);
+        if (proposed.isValid()) {
+            reply.set_timestamp(proposed.getTimestamp());
+        }
         reply.SerializeToString(&str2);
         break;
     default:

store/tapirstore/shardclient.cc

@@ -157,6 +157,7 @@ ShardClient::Prepare(uint64_t id, const Transaction &txn,
     request.set_op(Request::PREPARE);
     request.set_txnid(id);
     txn.serialize(request.mutable_prepare()->mutable_txn());
+    timestamp.serialize(request.mutable_prepare()->mutable_timestamp());
     request.SerializeToString(&request_str);
 
     transport->Timer(0, [=]() {

store/tapirstore/tapir-proto.proto

@@ -9,7 +9,7 @@ message GetMessage {
 
 message PrepareMessage {
     required TransactionMessage txn = 1;
-    optional uint64 timestamp = 2;
+    optional TimestampMessage timestamp = 2;
 }
 
 message CommitMessage {