vtd: Avoid spin-logging on empty RDB message queue

Instead loop in the transceiver's receive function until messages
arrive.

Author: clssn

plugins/vtd/src/rdb_codec.cpp

@@ -288,10 +288,6 @@ void RdbCodec::process(RDB_MSG_t* msg, bool& restart, cloe::Duration& sim_time)
 }
 
 void RdbCodec::step(uint64_t frame_number, bool& restart, cloe::Duration& sim_time) {
-  // TODO(ben): For some reason, this loop here goes round and round with zero
-  // messages received. Either we should stop dumping the log message when
-  // there are no messages to process, or we should have the receive function
-  // only return when there are messages?
   while (processing_frame_ || frame_number_ < frame_number || restart) {
     auto messages = rdb_->receive();
     rdb_logger()->trace("RdbCodec: processing {} messages [frame={}]", messages.size(),

plugins/vtd/src/rdb_transceiver_tcp.hpp

@@ -35,6 +35,8 @@
 #include "rdb_transceiver.hpp"  // for RdbTransceiver
 #include "vtd_logger.hpp"       // for rdb_logger
 
+#define VTD_RDB_WAIT_SLEEP_MS 1
+
 namespace vtd {
 
 /**
@@ -50,6 +52,9 @@ class RdbTransceiverTcp : public RdbTransceiver, public cloe::utility::TcpTransc
 
   std::vector<std::shared_ptr<RDB_MSG_t>> receive() override {
     std::vector<std::shared_ptr<RDB_MSG_t>> msgs;
+    while (!this->has()) {
+      std::this_thread::sleep_for(cloe::Milliseconds{VTD_RDB_WAIT_SLEEP_MS});
+    }
     while (this->has()) {
       num_received_++;
       msgs.push_back(this->receive_wait());