Thursday, July 2, 2020

jcmd Increasingly the Single JDK Command-line Tool to Rule Them All

What would you miss from the JDK command line tools jinfo, jmap, and jstack if those tools were no longer available?

I've been a fan of the command-line tool jcmd for a long time. I like that it combines features and functions of many other JDK command-line tools in a single tool. I also like that I like its interactive nature that supports my asking the tool what it's capable of for a given JVM process, meaning I don't have to remember exact options when applying its different functions.

Since its inception, jcmd has been taking on functionality from various other command-line JDK tools. In a recent post on the OpenJDK jdk-dev mailing list, Stephen Fitch announced a survey intended to "gather more information and help us evaluate and understand how others are using [three 'j* tools' jinfo, jmap, jstack] in the JDK." The surveyors are "specifically interested in your use-cases and how these tools are effective for you in resolving JVM issues."

Fitch explains the need for this survey:

We are considering deprecation and (eventual) removal of the jinfo, jmap, jstack - (aka “j* tools”) and building out a future foundation for some aspect of serviceability on jcmd, however we don’t have a lot of data about how how these tools are used in practice, especially outside of Oracle.

I'm encouraged that it sounds likely that jcmd will continue to add functionality under its single approach that was formerly available with different tools.

The survey will be open through 15 July 2020 and is an opportunity for Java developers to share their experiences and use cases with the JDK command line tools jinfo, jmap, and jstack so that it's more likely those use cases will be supported in jcmd (if not already supported) in the future. Fitch's post presents the URL for the survey:

Select jcmd Posts

Here are some of my previous posts regarding jcmd (I have used jcmd in numerous other posts to demonstrate various output as well):

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