Recently I upgraded a Spring-XD environment from 1.2.0.RELEASE to 1.3.0.RELEASE, which included an upgrade from Spring-Integration 4.1 to 4.2.
I had some dashboards monitoring JMX metrics for a custom module I'd written using Spring Integration, and I noticed that even when new messages came in on the input channel, the timeSinceLastSend was nearly always increasing, and never dropped back to 0.
The expected behavior is for the blue line to drop back fairly close to 0 whenever the yellow line goes up. In other words, timeSinceLastSend should go back to 0 the instant a new message is sent. This is how it worked in Spring-XD 1.2.0.RELEASE (and, by extension, Spring-Integration 4.1.x).