Rebase OW JavaRuntime to use OpenJDK 8

[kameshsampath]

Rebase OW JavaRuntime to fabric8 java image will help us to solve #5 as well making our community runtime image based out of openjdk.

[csantanapr]

Can you elaborate more on why fabric8 based on centos?
Instead of using standard openjdk image ubuntu/debian based?
https://hub.docker.com/_/openjdk/
https://github.com/docker-library/openjdk/blob/master/8-jdk/Dockerfile

this will benefits users that are use to extending the image with a layer by extending FROM and just adding libraries with apt-get

[kameshsampath]

Can you elaborate more on why fabric8 based on centos?

IMHO since its a redhat sponsored project we try to make the base image on centos - not sure I know any other reason.

this will benefits users that are use to extending the image with a layer by extending FROM and just adding libraries with apt-get

If the users want to build their won javaction images then let them do it via FROM with their needed libs, what we give as part of OW java8action is this one which is good to run java -jar <your app>

[csantanapr]

I would preferred to base it on a community based image instead
So I propose we use:
https://hub.docker.com/_/openjdk/
https://github.com/docker-library/openjdk/blob/master/8-jre/slim/Dockerfile

What do you think @Param-S ? We should be able to use this image and add any optimizations to the JVM 8 like Class-Cache and such

[csantanapr]

Let's do the image rebase on one PR first. and then build on top of it any other improvements.

[kameshsampath]

@csantanapr - the reason for using fabric8 images was that it right now works around with the JDK's inability to leverage cgroups by computing JVM_OPTS. Its also community based with centos and openjdk. If we wish to use the images said above we need spend time working on with the scripts for JVM Docker optimisation.

I would preferred to base it on a community based image instead

I am totally with you on this. I can remove Main class changes from the commit once we decide on base image to use.

[dinogun]

@csantanapr One option to look into would be the AdoptOpenJDK project. It is a OpenSource community effort to have a common build and test framework for OpenJDK across multiple platforms and hopefully in the future across distros as well. Docker images are published on a daily basis on DockerHub.
Please note that this is not TCK certified as yet (and hence the banner asking not to be used for production purposes), however TCK certification should only be a few days away now. Since the sources are being picked from the official mercurial repos (for OpenJDK with Hotspot), the feature set should be the same.
Eg cgroup mem limit can be turned on using -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap

[kameshsampath]

@csantanapr - rebased this commit with only OW Docker base image rebase and squashed all commits to one

[kameshsampath]

@dinogun - does this have jdk8 option ?

[dinogun]

@kameshsampath, yes, it currently supports jdk 8, 9 and 10 builds and the corresponding docker images too.

[kameshsampath]

since #24 takes care of moving JDK to openjdk we shall close this PR .

@csantanapr ???

[csantanapr]

I think you have other changes beyond moving to OpenJDK no?

[kameshsampath]

yes it does have some auto-classpath settings, some standard directories where the jars are stored and finally the most important one of running as non-root user. I can rebase it once we have #24 merged. WDYT ?

[kameshsampath]

@csantanapr https://github.com/kameshsampath/adoptopenjdk check that project that has the AdoptOpenJDK based jdk8/jdk9 images for both centos/debian. Wondering if we can move it under OW github repo

[csantanapr]

I think this is already done by #24