do not flush without a reason

lib/karafka/web/processing/consumer.rb

@@ -26,6 +26,7 @@ def initialize(*args)
 
           # We set this that way so we report with first batch and so we report as fast as possible
           @flushed_at = monotonic_now - @flush_interval
+          @changed = false
         end
 
         # Aggregates consumers state into a single current state representation
@@ -59,6 +60,10 @@ def consume
             @state_aggregator.add(message.payload, message.offset)
             @metrics_aggregator.add_report(message.payload)
             @metrics_aggregator.add_stats(@state_aggregator.stats)
+            # Indicates that we had at least one report we used to enrich data
+            # If there were no state changes, there is no reason to flush data. This can occur
+            # when we had some messages but we skipped them for any reason
+            @changed = true
 
             # Optimize memory usage in pro
             message.clean! if Karafka.pro?
@@ -73,20 +78,20 @@ def consume
 
         # Flush final state on shutdown
         def shutdown
-          return unless @state_aggregator
-
-          materialize
-          validate!
-          flush
+          dispatch
         end
 
         private
 
         # Flushes the state of the Web-UI to the DB
         def dispatch
+          return unless @changed
+
           materialize
           validate!
           flush
+
+          @changed = false
         end
 
         # @return [Boolean] is it time to persist the new current state