Functional unit and integration tests are a common practice to detect and prevent regressions within a software component or application's behavior. Things look different, though, when it comes to performance-related aspects: how to identify an application is slower than it used to be? How to spot higher memory consumption than before? How to find out about sub-optimal SQL queries that sneaked in? Any performance tests based on metrics like wall-clock time or through-put are not portable. They are subject to a specific execution environment such as a developer laptop, CI, or production-like environment. Welcome JfrUnit: based on the JDK Flight Recorder (JFR), it allows you to implement assertions based on all kinds of JFR events emitted by the JVM or your application. JfrUnit makes it very easy to identify potential performance issues by asserting metrics that may impact your application's performance, like an increased object allocation rate, retrieval of redundant data from the database, loading of unneeded classes, and much more. Come and join us for this code-centric session to learn about: Using JDK Flight Recorder and JfrUnit for implementing performance regression tests Emitting JFR events from 3rd party libraries using JMC Agent Analyzing performance regressions in JDK Mission Control

1. Continuous Performance Regression
Testing With JfrUnit
Gunnar Morling
Software Engineer, Red Hat
@gunnarmorling

2. #JfrUnit @gunnarmorling
Today’s Objective: Learn about...
1. Implementing performance regression tests with JDK
Flight Recorder and JfrUnit
2. Analyzing performance regressions in JDK Mission Control
3. Emitting JFR events from 3rd party libraries

3. #JfrUnit @gunnarmorling
3
Gunnar Morling
● Open source software engineer at Red Hat
○ Debezium
○ Quarkus
● Spec Lead for Bean Validation 2.0
● Java Champion
● @gunnarmorling

4. #JfrUnit @gunnarmorling
Challenges of Performance Tests
● Tests based on throughput or latency are dependent on
specifics of the environment
○ Require production-like set-up
○ Impacted by unrelated concurrent load (e.g. on CI server)

5. #JfrUnit @gunnarmorling
● Assert metrics like memory allocation, or IO
○ Based on JDK Flight
Recorder events
○ Failures may indicate a
performance regression
● Plain unit tests
● Analyse in JDK Mission Control
JfrUnit — Assert Performance Impacting Metrics

6. #JfrUnit @gunnarmorling
Tools
© James Petts https://flic.kr/p/LgibJR (CC BY-SA 2.0)

7. #JfrUnit @gunnarmorling
● “Troubleshooting, monitoring, and profiling
framework embedded into the JVM”
● 150+ built-in event types; custom ones
● Open-source since Java 11
(backported to 8)
● Low overhead, meant for “always-on”
● Accessible via recording files
and streaming
OpenJDK Flight Recorder

8. #JfrUnit @gunnarmorling
https://bestsolution-at.github.io/jfr-doc/
JFR Event Types

9. #JfrUnit @gunnarmorling
● Control, visualize, and
analyze JFR recordings
● And more:
○ JMX console
○ heap dump analyzer
○ etc.
OpenJDK Mission Control

10. #JfrUnit @gunnarmorling
Demo
© Wall Boat https://flic.kr/p/Y6zkmX (Pubic Domain)

11. #JfrUnit @gunnarmorling
Hello, JfrUnit!

12. #JfrUnit @gunnarmorling
● Robust tests with very fast feedback cycle
○ Independent from environment
○ Proactive identification of issues
● Metrics need solid understanding; e.g. increased allocation may
or may not be a problem
● Cannot identify all issues, e.g. locks showing up only under load
● Won’t help with issues elsewhere, e.g. a bad query execution plan
JfrUnit — Discussion and Limitations

13. #JfrUnit @gunnarmorling
Wrap-Up
© Maria Eklind https://flic.kr/p/251HmVw (CC BY-SA 2.0)

14. #JfrUnit @gunnarmorling
● JfrUnit: a tool in the performance testing box
○ Complement - no replacement - for other tests
● JMC Agent: produce events from code not under your control
● Move beyond Java 1.8 🚀
Take Aways

15. #JfrUnit @gunnarmorling
https://horreum.hyperfoil.io/
Outlook — Keeping Track of Historic Values

16. #JfrUnit @gunnarmorling
● JfrUnit
https://github.com/moditect/jfrunit
● Introduction to JfrUnit
https://www.morling.dev/blog/towards-continuous-performance-regression-
testing/
● Introduction to JMC Agent
https://developers.redhat.com/blog/2020/10/29/collect-jdk-flight-recorder
-events-at-runtime-with-jmc-agent/
● Profiling Java inside containers with ContainerJFR
https://developers.redhat.com/devnation/tech-talks/containerjfr
Resources

17. #JfrUnit @gunnarmorling
Q&A
gunnar@hibernate.org
@gunnarmorling
📧