Inspecting the Runtime with VisualVM
VisualVM is a graphical user interface (GUI) for monitoring a JVM, profiling a running application, and analyzing heap dumps. It comes packaged with the JDK, so there’s no need to install it. As long as the java command is on your PATH, you’re ready to go. Run this command to start VisualVM:
This opens the GUI, where you’ll see a list of applications in the left sidebar. There are groups for local and remote JVM applications. At a minimum, you’ll see the VisualVM process listed under Local. If you have some other Java processes running, you’ll also see those.
Open a new terminal window and move into the Twitalytics directory. Now start your JRuby server with Puma so VisualVM can connect ...