Marcus Hirt

Since this month is Hacktoberfest, I thought it would be a good idea to talk a bit about how to contribute to the OpenJDK Mission Control project.

Yay, the latest release of JDK Mission Control was just released!

Since this is the source release, it may still take a bit of time until the downstream vendors release binary builds of JDK Mission Control 8.1.0.

The 8.0.1-ga tag was just set in the jmc8 repository on GitHub.

This is a patch update release, and will therefore not include any new features.

The next upcoming source release is JMC 8.1.0, which will contain new features and enhancements. The planned source release date for JMC 8.1.0 is the 2nd of August 2021.

The JDK Flight Recorder design philosophy is to be the one-stop-shop production profiler for OpenJDK.

JFR needs to be able to do various kinds of profiling, all at the same time, at a low overhead. It also needs to be able to run continuously for as long as someone is interested in the data. Potentially always.

Now, with changes in the Java (and the computing) ecosystem, JFR has some loom-ing challenges to remain relevant for the future.

I’ve gotten a lot of questions about continuous production profiling lately. Why would anyone want to profile in production, or, if production profiling seems reasonable, why the heck leave it on continuously?

I thought I’d take a few moments and share my take on the problem and the success I’ve seen the past years applying continuous production profiling in systems in the real world.

Profiling these days is no longer limited to high overhead development profilers. The capabilities of the production time profilers are steadily increasing and their value is becoming less controversial, some preferring them for complex applications even during development.

Since JDK 14, there is a new kid on the block – Java Flight Recorder streaming, which enables developers to subscribe to JFR data.

It is a feature allowing a developer to subscribe to select JFR data and to decide what to do with that data in the host process. JFR events can also be consumed from a separate process by pointing to the file repo of a separate JVM process – the mechanism is the same.

OpenJDK, being open sourced, has builds provided by plenty of vendors. Here is a non-exhaustive list of some vendors shipping supported versions of OpenJDK (in alphabetical order, distribution(s) in parenthesis):

– AdoptOpenJDK
– Alibaba (Dragonwell)
– Amazon (Corretto)
– Azul (Zulu, Zing)
– BellSoft (Liberica)
– Red Hat (Red Hat Builds of OpenJDK)
– Oracle (Oracle JDK, Oracle OpenJDK)
– SAP (SapMachine)