Of course Java-monitor already worked fine for Resin, showing heap memory and file descriptors. Now we added Resin's HTTP and database connection pools to the monitored resources. Java-monitor shows you how many HTTP threads your Resin server has and how many database connections are allocated and active.
One of our testers discovered that his production machine was configured to have a maximum of two (2) database connections. Woops. Just helping us test the new probe before the release helped him resolve a bottleneck and potential production incident. Here you can see his database pool graph, which starts out with a maximum of 2 and now has been reconfigured to have a maximum of 32 connections.