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

#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 

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

#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) 

#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 

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

#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 

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

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

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

#JfrUnit @gunnarmorling Hello, JfrUnit! 

#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 

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

#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 

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

#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 

#JfrUnit @gunnarmorling Q&A [email protected] @gunnarmorling 📧 

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