fix: modified code to use flush() when internal queue is not loaded

https://telecominfraproject.atlassian.net/browse/WIFI-13597

NOTE: This is port of https://github.com/Telecominfraproject/wlan-cloud-ucentralgw/pull/362

Signed-off-by: Ivan Chvets <ivan.chvets@kinarasystems.com>

src/framework/KafkaManager.cpp

@@ -107,7 +107,16 @@ namespace OpenWifi {
 					NewMessage.partition(0);
 					NewMessage.payload(Msg->Payload());
 					Producer.produce(NewMessage);
-					Producer.flush();
+					if (Queue_.size() < 100) {
+						// use flush when internal queue is lightly loaded, i.e. flush after each
+						// message
+						Producer.flush();
+					}
+					else {
+						// use poll when internal queue is loaded to allow messages to be sent in
+						// batches
+						Producer.poll((std::chrono::milliseconds) 0);
+					}
 				}
 			} catch (const cppkafka::HandleException &E) {
 				poco_warning(Logger_,
@@ -117,8 +126,13 @@ namespace OpenWifi {
 			} catch (...) {
 				poco_error(Logger_, "std::exception");
 			}
+			if (Queue_.size() == 0) {
+				// message queue is empty, flush all previously sent messages
+				Producer.flush();
+			}
 			Note = Queue_.waitDequeueNotification();
 		}
+		Producer.flush();
 		poco_information(Logger_, "Stopped...");
 	}
 
@@ -324,4 +338,4 @@ namespace OpenWifi {
 											   partitions.front().get_partition()));
 	}
 
-} // namespace OpenWifi
+} // namespace OpenWifi