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Troubleshooting via jmxterm

If you are having difficulties with nrjmx to get data out of your JMX service, this interactive CLI tool could help you out in the process.

Install

You can get it from https://docs.cyclopsgroup.org/jmxterm

Or via your usual package manager. Ie, for Mac:

brew install jmxterm

Connect

As jmxterm is an interactive CLI REPL, you could simple launch jmxterm and then open <URL>. URL can be a <PID>, <hostname>:<port> or full qualified JMX service URL. For example:

 open localhost:7199,
 open jmx:service:...

There's an option to open connection before getting into the REPL mode via -l/--url argument, ie:

jmxterm -l localhost:7199

Connectivity issues

If you face connection issues with nrjmx you can specify the connection URL in the same way via -C/--connURL argument, ie:

jmxterm -l service:jmx:rmi:///jndi/rmi://localhost:7199/jmxrmi
nrjmx   -C service:jmx:rmi:///jndi/rmi://localhost:7199/jmxrmi

Verbose

There's a verbose mode that will help with extra information output when troubleshooting in both tools:

jmxterm -v/--verbose
nrjmx   -v/--verbose

Query

We are interested on fetching:

  • from a JMX domain
  • some MBean objects
  • and some MBean attributes

JMX MBeans queries are launched in nrjmx using a glob pattern matching query against both DOMAIN and BEAN object. All readable bean attributes and values fill be retrieved.

The way to do so on nrjmx is concatenating both with the : separator, like: "DOMAIN_PATTERN:BEAN_PATTERN".

For instance to retrieve:

  • all beans ":"
  • all beans of type Foo ":type=Foo,"
  • beans from domain Bar and type Foo "Bar:type=Foo,*"

If there are issues while fetching these values possible errors like java.lang.UnsupportedOperationException will be printed by nrjmx into stderr output.

You can navigate through your exposed JMX data using jmxterm REPL mod.

  • domains list available domains
  • domain <DOMAIN_NAME> will set current domain
  • beans list available MBeans within your current domain

Querying at jmxterm uses the same glob fashion mode. Just take into account that this tool divides DOMAIN and BEAN queries in 2 steps. So you can use

  • domain <PATTERN> causes subsequent bean queries to run against matched domains, ie * unsets the domain
  • bean sets or retrieves bean from current domain context,*` unsets the domain
  • get ` fetches bean attributes info from current domain & bean context

A one liner query is possible as well, ie for querying all available attributes: get -d DOMAIN -b BEAN *

Help

Both tools provide extra help via:

jmxterm -h/--help
nrjmx   -h/--help