(oh look, a proper blog post!)
JMX is the de-facto standard in the Java and JVM-based world for exposing service metrics, and feeds nicely to tools like Graphite using JMXTrans and others. However, it’s pretty obtuse and over-complex, and it can be hard to figure out what path the JMX metrics will show up under once deployed.
Unfortunately, once a JVM-based service is deployed to EC2, it becomes very difficult to use jconsole to connect to it, due to deficiencies and crappy design in the JMX RMI protocol (I love the way they reinvented the broken parts of IIOP in that respect). Don’t even bother; instead, use jmxsh: https://code.google.com/p/jmxsh/ .
To use this, you need to modify the service process’ command line to include the following JVM args, so that the remote JMX API is exposed:
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=16660 -Dcom.sun.management.jmxremote.local.only=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false
Change the port number if there is already a process running on that port. Ensure the port isn’t accessible from off-host; in EC2, this should be safe enough to use once that port number is not in the EC2 security group.
Go to https://code.google.com/p/jmxsh/downloads/list and download the latest jmxsh-FOO.jar; e.g. ‘wget https://jmxsh.googlecode.com/files/jmxsh-R5.jar’. Then on the host, as the UID the service is running under, run: ‘java -jar jmxsh-R5.jar -h 127.0.0.1 -p 16660’. You can then hit “Enter” to go into “Browse Mode”, and you’ll get text menus like this:
==================================================== Attribute List: 1. -r- long MaxFileDescriptorCount 2. -r- long OpenFileDescriptorCount 3. -r- long CommittedVirtualMemorySize 4. -r- long FreePhysicalMemorySize 5. -r- long FreeSwapSpaceSize 6. -r- long ProcessCpuTime 7. -r- long TotalPhysicalMemorySize 8. -r- long TotalSwapSpaceSize 9. -r- String Name 10. -r- int AvailableProcessors 11. -r- String Arch 12. -r- double SystemLoadAverage 13. -r- String Version SERVER: service:jmx:rmi:///jndi/rmi://127.0.0.1:16660/jmxrmi DOMAIN: java.lang MBEAN: java.lang:type=OperatingSystem ====================================================
Navigate through the MBean tree looking for good Attributes which would make good metrics (5 in the list above, for example). Note the MBean and the Attribute names.