vgw: add more comments and logs

server/videogateway.cc

@@ -289,6 +289,8 @@ int setupRouter(void **ctx, void **s, string addr, int rcvQS=0)
     if(rcvQS !=0) {
         zmq_setsockopt(*s, ZMQ_RCVHWM, &rcvQS, sizeof(rcvQS));
     }
+
+    spdlog::info("zmq binding {}", addr);
     ret = zmq_bind(*s, addr.c_str());
     if(ret < 0) {
         spdlog::error("failed to bind zmq at {} for reason: {}, retrying load configuration...", addr, zmq_strerror(zmq_errno()));
@@ -314,6 +316,7 @@ int main()
         darwinUrl = string(darwinUrl_);
     }
 
+    // set log level
     auto logLevel_ = getenv("LOG_LEVEL");
     if(logLevel_) {
         spdlog::set_level(spdlog::level::from_str(logLevel_));
@@ -323,6 +326,7 @@ int main()
         spdlog::set_level(spdlog::level::debug);
     }
 
+    // setup zmq, listening incoming connections
     string addr = "tcp://0.0.0.0:7123";
     if(setupRouter(&pRouterCtx, &pRouter, addr)<0) {
         exit(1);
@@ -372,9 +376,13 @@ int main()
                 if(deviceMap.count(sn) == 0) {
                     deviceLock.emplace(sn, new mutex());
                     deviceMap.emplace(sn, new packet_processor_t());
+                    spdlog::info("add camera {} to device map", sn);
                     deviceMap[sn]->sn = sn;
                 }
             }
+
+            // for the first packet, change the transmitting state and start a thread to handle 
+            // incoming packets.
             if(deviceMap[sn]->state == 0) {
                 deviceMap[sn]->state = 1;
                 thread thWorker = thread(fn_worker, deviceMap[sn]);
@@ -383,6 +391,8 @@ int main()
                 }
             }
 
+            // for each camera, we cache at most 10 packets in a queue, when overflow, remove the earliest one
+            // before pushing to queue.
             {
                 lock_guard<mutex> lg(*deviceLock[sn]);
                 if(deviceMap[sn]->pktQue.size() > 10) {