emy0295 / java

s2i-java-example

This S2I example is intentionally NOT using Spring Boot, Vert.x, Dropwizard, Wildfly Swarm or whatever other simple "fat JAR" (non-WAR/EAR) Java server framework, but for clarity simply uses the simplest possible Java server application with a main() class. You can easily apply this example to whatever standalone Java application you want to container-ize with S2I. (We're using the Java built-in com.sun.net.httpserver.HttpServer; JUST for illustration of S2I.)

Since fabric8io-images/s2i#127, this is integrated in & part of fabric8io-images, and will continue to be maintained there instead of here.

Local

For local building, install s2i either from source https://github.com/openshift/source-to-image/releases/ or e.g. via:

sudo dnf install source-to-image

Now to build the simplest possible Java server with OpenShift Source-To-Image (S2I) using the fabric8io-images/s2i builder:

s2i build https://github.com/vorburger/s2i-java-example fabric8/s2i-java vorburger:s2i-java-example

or

git clone https://github.com/vorburger/s2i-java-example ; cd s2i-java-example
s2i build --copy . fabric8/s2i-java vorburger:s2i-java-example

NB The --copy ensures that the latest content of the current directory and not only it's commited .git content is used (see S2I #418).

Now run it like this:

docker run -p 8080:8080 vorburger:s2i-java-example

and see "hello, world" when accessing http://localhost:8080 - it works!

OpenShift

To do the same as above directly inside your OpenShift instance like this:

oc new-app fabric8/s2i-java~https://github.com/vorburger/s2i-java-example
oc expose svc/s2i-java-example --port=8080
oc status
minishift openshift service s2i-java-example --in-browser

TODO this is still NOK due to a missing EXPOSE 8080 in the Dockerfile of fabric8/s2i-java, see fabric8io-images/s2i#115 :-(

NB that you cannot really build from "the latest sources from the local filesystems", because there is no s2i build --copy equivalent; attempting to do e.g. oc new-app fabric8/s2i-java~. just fetches from the first git remote of ./.git ... :-(

Advanced

Container options

All JVM options documented on https://github.com/fabric8io-images/s2i/tree/master/java/images/jboss are typically specified in .s2i/environment, but for quick testing can obviously also be specified on the docker run CLI like so:

docker run -e "JAVA_MAIN_CLASS=ch.vorburger.openshift.s2i.example.Server" -p 8080:8080 vorburger:s2i-java-example

fabric8io-images/s2i self build locally and in OpenShift

If you want to use latest fabric8/s2i-java from source instead of an older image on hub.docker.com, then you can do that. Here's how for local Docker:

docker build https://github.com/fabric8io-images/s2i.git#master:java/images/jboss

or:

git clone https://github.com/fabric8io-images/s2i.git
cd java/images/jboss
docker build . -t fabric8/s2i-java

and inside OpenShift:

oc new-build https://github.com/fabric8io-images/s2i.git --context-dir=java/images/jboss

NB As above, you cannot really build from "the latest sources from the local filesystems", but you can push in-development changes to a remote and test that, like this:

oc new-build https://github.com/YOURID/s2i.git#GITBRANCH --context-dir=java/images/jboss

and then test using that like this:

oc new-app s2i~https://github.com/vorburger/s2i-java-example

How to clean up

oc delete imagestream s2i-java
oc delete imagestream s2i-java-example
oc delete build s2i-java-example-1
oc delete buildconfig s2i-java-example
oc delete deploymentconfig s2i-java-example
oc delete service s2i-java-example

TODO points

• Why isn't it incremental? Keeps re-downloading Maven basics, every time..
• Support Gradle! see fabric8io-images/s2i#121 and the gradle branch on this repo
• Monitoring..
• Sources should not be runtime container?!

More background

• https://github.com/fabric8io-images/s2i
• https://github.com/fabric8io-images/s2i/tree/master/java/images/jboss
• fabric8io-images/s2i#112
• https://github.com/openshift/source-to-image