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OpenShift Spring Boot S2I

Builder Image

The following tables describes the files used in this image.

File Required? Description
Dockerfile Yes Defines the base builder image
s2i/bin/assemble Yes Script that builds the application
s2i/bin/usage No Script that prints the usage of the builder
s2i/bin/run Yes Script that runs the application
s2i/bin/save-artifacts No Script for incremental builds that saves the built artifacts
test/run No Test script for the builder image
test/test-app No Test application source code

Dockerfile

Builds the builder image itself, installing Maven and Gradle and using OpenJDK as base image.

S2I scripts

Called by OpenShift for the lifecycle of the application.

assemble

  • Copies the Spring Boot Application source from /tmp/src to /opt/app-root/src
  • Determines the build type from the BUILD_TYPE environment variable
  • Executes a build of the application using the determined build typen, if a pom.xml is detected
  • The build artifact is copied to /opt/openshift and a new image with the Spring Boot Application for OpenShift is created
  • To support deployment of already built Spring Boot JAR applications in OpenShift a runtime image is created when no pom.xml is detected. The JAR must be present in the /tmp/src directory.

To reduce build time, any saved artifacts from the previous image build are restored.

run

The run script is used to start/run the Spring Boot application in OpenShift.

save-artifacts (optional)

The save-artifacts script allows a new build to reuse content (dependencies) from a previous version of the application image.

Create the Spring Boot Application S2I builder image

The following command will create a S2I builder image named spring-boot based on the Dockerfile. Use the OpenShift Docker, f.e. eval $(minishift docker-env)

docker build -t spring-boot .

Creating the Application Container Image

The application container image contains the built application binary which is layered on top of the builder (base) image. The following command will create the application container image:

Usage:

s2i build <location of source code> <S2I builder image name> <application container image name>

s2i build test/test-app spring-boot boot-app
---> Building and installing application from source...

Based on the logic defined in the assemble script, s2i will create an application container image using the supplied S2I builder image and the application source code from the test/test-app directory.

Running the application container image

Running the application image is as simple as invoking the docker run command:

docker run -d -p 8080:8080 boot-app

The application boot-app, should now be accessible at http://localhost:8080.

Using the saved artifacts script

Rebuilding the application using the saved artifacts can be accomplished using the following command:

s2i build --incremental=true test/test-app spring-boot boot-app
---> Restoring build artifacts...
---> Building and installing application from source...

This will run the save-artifacts script which includes the code to backup the currently running application dependencies. When the application container image is built next time, the saved application dependencies will be re-used to build the application.

Using the OpenShift Spring Boot Application S2I builder image

Create the S2I builder image and push it to the integrated docker registry for the current project:

oc new-build --strategy=docker --name=spring-boot https://github.com/trion-development/openshift-spring-boot-s2i.git

It can now be used for a build

oc new-build spring-boot~https://github.com/trion-development/spring-boot-rest-sample.git

To be able to use it for creating deployment through the UI upload the template to the current project:

curl -Ssl https://raw.githubusercontent.com/trion-development/openshift-spring-boot-s2i/master/spring-boot-s2i.json | oc create -f -

Open the OpenShift web console (Browser UI) and open the current project. Click "Add to Project" in the upper right, choose "Select from project" and use the "spring-boot" template. Specify the application details.

After clicking 'create' the following steps will be performed:

  • Application build
  • Creation of application container image
  • Image push to OpenShift Docker Registry
  • Creation of a deployment of the applicatoin as a pod