There are 4 Java agents in one servers. All the agents show that it is connected to Dynatrace server. One of the agents are not collecting data and no PurePaths is displayed for that particular agent. All the agents are connected to one Agent Group. Any idea how I can go about finding out the reason why just one agent is not showing any Purepath?
One place to look is the agent log files. Perhaps there's a nugget in there that's different in the non-reporting agent log.
If the log file does not provide any clues, I would look at the AgentOverview dashlet. For each agent row, theres a column called "Event count". Is it increasing? Refresh the dashlet a few times to see if the event count increases. If it's increasing, then you're getting traffic from that JVM, just no traffic that's worthy of creating a purepath. If true, I would validate that the JVM isn't mapped to a different agentgroup, where the agentGroup has the Servlet sensor unplaced, or disabled.
I would expect all these JVMs to be mapped to the same agent group? AgentOverview dashlet should help with this question. If they're not in the same gropu, try renaming to map into the same agent group as another working JVm and see if that makes the PPs appear, if this works, then you have some unplaced or misconfigured sensors.
You could also explore whether there's any traffic going to the idle JVM at all, from an outside perspective. Is there another source of traffic you could use to validate? JVM log?