This project has been retired

While it served me well for years, my apps have now moved on from Openshift.

Spring Boot - Maven 3 - CentOS Docker image

This repository contains the sources of the base image for deploying Spring Boot applications as reproducible Docker images. The resulting images can be run either by Docker or using S2I with a prepared s2i.json file.

This image is heavily inspired by the awesome codecentric/springboot-maven3-centos builder image.

Usage

To build a simple springboot-sample-app application using standalone S2I and then run the resulting image with Docker execute:

$ s2i build git://github.com/codecentric/springboot-sample-app skjolber/spring-boot-maven3-jdk8-centos springboot-sample-app
$ docker run -p 8080:8080 springboot-sample-app

Accessing the application:

$ curl 127.0.0.1:8080

Import to Openshift

Add using

$ oc create -n <your project name> -f s2i.json

and remove using

$ oc delete -n <your project name> -f s2i.json 

Secrets

If you are using a private repository, add SSH keys using

$ oc secrets new-sshauth <secret name> --ssh-privatekey=$HOME/.ssh/my_openshift_key_rsa

and remember to use SSH style git repository URLs.

The secret must be manually configured on the generated build (under advanced options), or can be automatically matched against your git repo.

Environment variables

• APP_TARGET (default: '')

  This variable specifies a relative location to your application binary inside the container.

• MVN_ARGS (default: '')

  This variable specifies the arguments for Maven inside the container.

• JAVA_OPTS (default: '')

  Additional Java options, like garbage collector and such.

• XMX (default: '256')

  Java memory

• XMS (default: '32')

  Java memory in megabytes.

• SPRING_ACTIVE_PROFILES (default: 'default')

  Active spring profiles (comma-seperated).

Repository organization

• s2i/bin/

  This folder contains scripts that are run by S2I:

  • assemble

    Is used to restore the build artifacts from the previous built (in case of 'incremental build'), to install the sources into location from where the application will be run and prepare the application for deployment (eg. using maven to build the application etc..)

  • run

    This script is responsible for running a Spring Boot fat jar using java -jar. The image exposes port 8080, so it expects application to listen on port 8080 for incoming request.

  • save-artifacts

    Not currently supported

Testing

In order to test your changes to this STI image or to the STI scripts, you can use the test/run script. Before that, you have to build the 'candidate' image:

$ docker build -t skjolber/spring-boot-maven3-jdk8-centos-candidate .

or

$ docker build --network host -t skjolber/spring-boot-maven3-jdk8-centos-candidate:v123 .

After that you can execute ./test/run. You can also use make test to automate this.

Tuning

I'm using a set of default JVM parameters:

-Djava.security.egd=file:/dev/./urandom 
-Djava.awt.headless=true 
-Dfile.encoding=UTF-8
-XX:+UseG1GC 

Memory usage

My Openshift pods seem to be using more memory than expected. While this is a complex topic, I've come up with a few parameters for reducing the footprint. As in (almost) all optimization, measuring first is important.

Web container

The Undertow web container seems to be least memory hungry.

JMX

To get an overview of the memory use Java Misson Control or JConsole with JMX. Enable JMX and run port-forwarding to your pod. Add Java parameters

-Dcom.sun.management.jmxremote.port=8090 -Dcom.sun.management.jmxremote.rmi.port=8090 -Djava.rmi.server.hostname=127.0.0.1 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false

and start port-forwarding using

oc port-forward <pod> 8090:8090

and connect to localhost:8090.

JVM memory parameters

After making sure all code paths have been visited, and running some simple benchmarks, I arrived at the following:

Name	Default	Parameter
Compressed class size	1 GB	-XX:CompressedClassSpaceSize=16m
Metaspace	Unlimited	-XX:MaxMetaspaceExpansion=0 -XX:MaxMetaspaceSize=64m
Reserved code cache	32M/48M	-XX:ReservedCodeCacheSize=24m

Image memory parameters

While some memory leak has been fixed in the latest version of Java 8 (152), some additional parameters can be used to reduce memory. Add the following environment variables:

export MALLOC_ARENA_MAX=2
# disable dynamic mmap threshold, see M_MMAP_THRESHOLD in "man mallopt"
export MALLOC_MMAP_THRESHOLD_=131072
export MALLOC_MMAP_THRESHOLD_=131072
export MALLOC_TOP_PAD_=131072
export MALLOC_MMAP_MAX_=65536

Result

Using these parameters, and 128m Xmx, I was able to get a 35 MB Spring Boot app to use about 360 MB (as reported by Openshift metrics). Obiously you'll want to add some margin, or the pod will be terminated with OOM error.

Copyright

Released under the Apache License 2.0. See the LICENSE file.

See also

• http://trustmeiamadeveloper.com/2016/03/18/where-is-my-memory-java/
• https://spring.io/blog/2015/12/10/spring-boot-memory-performance