1. „Oracle Code ONE 2018“ JVM CPU & Memory Settings
for docker containers in production
DEV6060
Andreas Hochleitner

2. Starting questions Orientation and/or background
Technical, dev, ops, business, sales, management
Which JDK are you using in PRODUCTION
(<=u121, <=u131) <7
Who is using … in Production
Containers: Docker, LXC, ..
Orchestration: Kubernetes, Docker Swarm, Rancher, ..

3. Java Dev Perspective: impact of production platform to the Java Development
No impact
Slight impact
Huge impact

4. My professional background
Studies Informatics at Technical University Vienna (TU Wien) / Austria
30 years in the IT business
Development centric
> 20 years Java / JavaEE (J2EE)
> 10 years independant consultant as Architect

5. Current projects
Consulting JavaEE-Product Development for Startup (development, process, state-of-the-art)
Solution Architect in a large component-oriented Landscape (JavaEE, CI/CD, strong integration aspects)
Wildfly / Jenkins / Groovy / Docker / Kubernetes

6. Prerequisites for this talk
Basic Docker Knowhow
Basic Kubernetes Knowhow
Basis Linux Knowhow

7. Structure 1 Background – Motivation 2 Overview 3 JDK – 7 8 9 10 11
4 Container-Basis: Docker - K8S
5 Different Aspects with examples
Memory
CPU
Threads
6 Summary

8. 1 Background – Motivation
Last JavaOne Session „Java inside docker: What you must know to not FAIL“ Rafael Benevides, Burr Sutter
Different articles/blogs about „Don‘t use Java in Containers“ or „How to not fail using Java in Containers“
JDK 9 – special parameters
-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap
Backported to JDK 8 u131
Master-Agent-Jenkins in OnPrem-Kubernetes ==> OOM Killer Problem

9. 2 Overview Production oriented
JDK versions are not arbitrarily choosable
Moving existing applications into container directions
What you must know?
Which problems can occur?
How to deal with or fix the problems?

10. 3 JDK – 7 8 9 10 11 Examples are based on OpenJDK from DockerHub
OpenJDK 8u121
OpenJDK 8 (8u181)
OpenJDK 9
OpenJDK 10
(OpenJDK 11)

11. 4 Container-Basis: Docker - K8S
Docker ce on Linux (Ubuntu 16.04)
Kubernetes OnPrem (large K8S-Cluster, Minikube)

12. Docker – Mini Basics What are Docker Containers
Linux cgroups & namespaces
Dockerfile
„docker build“
„docker run“

13. Kubernetes – Mini Basics
Kubernetes Cluster
What is a Pod?
Kubectl
Manifest-File (yaml-file)

14. Basic Problem
JVM in a container sees Host Settings and not Cgroup-Settings
Depending on JDK version
OOM Killer (out-of-memory killer)

15. Different Aspects with examples
Memory
CPU
Threads

16. JDK 10 Ergonomics Process to improve application performance by
JVM and
Garbage collection heuristics (behavior-based heuristics)
Server class
2 or more physical processors
2 or more GB of physical memory

17. JDK 10 Ergonomics Server class defaults Similar to other JDKs
Garbage-first (G1) collector
Inital heap size of 1/64 of physical memory
Maximum heap size of ¼ of physical memory
Tiered compiler, using both C1 andC2
Similar to other JDKs

18. JDK 9 Improvements (8 backport)
-XX:+UnlockExperimentalVMOptions
-XX:+UseCGroupMemoryLimitForHeap
(-XX:MaxRAMFraction=1)
With these Settings JVM will use Cgroup-infos, and not Host-infos

19. JDK 10 Container Support (improvements)
Improve docker container detection and resource configuration usage JDK )
-XX:-UseContainerSupport
-XX:ActiveProcessorCount=count
Allow more flexibility in selecting Heap % of available RAM (JDK )
-XX:InitialRAMPercentage
-XX:MaxRAMPercentage
-XX:MinRAMPercentage
attach in Linux should be relative to /proc/pid/root and namespace aware (JDK )
-XX:+UseContainerSupport is default

20. JVM Settings for the worst case
-XX:ParallelGCThreads
-XX:CICompilerCount
-Xmx
-XX:+UnlockExperimentalVMOptions
-XX:+UseCGroupMemoryLimitForHeap

21. 6 Summary Understand your JVM application
Memory
Cpu usage
Thread counts
Analyse & test your concrete JVM in realistic production environment
Use up-do-date JDK version (11 → 10 → 9 → 8 → 7) as far it is possible
Set JDK/Container/Pod-Settings according to availablilty

22. Q & A

23. Thank You!
Mail: