Java application monitoring over longer time periods?

Question

Using tools like JConsole I can monitor a Java application real time. How can analyze the performance over a longer time period? Let's say over a day? Or week?

Are there simple tools like jConsole I can use?

Answer 1

There are options for the generic "monitor as much parameters as we can" approach:

• Command line: jcmd <PID|main class> PerfCounter.print (ref) – you will then need to wrap your head around the names of the properties it outputs, schedule running this periodically, store the data somewhere, visualize it yourself.
• A lot (all?) of this information is also exposed by JMX beans. You can then find them out (you can see them and what they export in JConsole for example), and using a command-line tool like e.g. jmxterm you can record the values and visualize them. Same procedure: schedule yourself, record, visualize yourself. It's not too user-friendly, so why I am mentioning this approach is that...
• ...people usually use a specialized monitoring system (think Graphite, Zabbix, Logstash/Kibana etc. — I am throwing these in just as keys for search together with "Java/JVM/JMX/JFR") that can collect information from Java processes through JMX and nicely present it. Periodic running, storing the timeseries data, visualization is solved by these systems.
• JFR ("Java Flight Recorder") is a mechanism built into the JVM that allows to have continuous recording of many JVM + system metrics, dumps them into a file periodically, then you can visualize these with JMC ("Java Mission Control"). It is "cheaper" in the sense that you do not need to install/support a separate monitoring system, but is less accessible (unless paired with a monitoring system): you need to collect, download, process files.

In addition to these, there is jstat which is basically the same as jcmd ... PerfCounter.print, but mostly for memory-related metrics, it has the "run periodically" functionality built in and presents results slightly differently (one "recording" – 1 line).

I would say: if you need to do it once or occasionally, be it over a longer period, and need just a few parameters, like memory/number of threads/..., then target using jstat, jcmd PerfCounter.print; if you need more parameters, then JFR/JMC. If you need it as something that runs alongside your system, always collecting and present, available to people not having admin rights in the system where the JVM resides, then look into the monitoring systems and their integration with Java applications.