An OpenShift Source-to-Image builder dedicated to Go

Installation / usage

Using Docker

Create the builder image

The following command will create a builder image named golang-centos7.

docker build -t golang-centos7 .

Testing the builder image

The builder image can be tested using the following commands:

docker build -t golang-centos7-candidate .
IMAGE_NAME=golang-centos7-candidate test/run

Creating the application image

The application image combines the builder image with your applications source code, which is served using whatever application is installed via the Dockerfile, compiled using the assemble script, and run using the run script. The following command will create the application image:

s2i build test/test-app golang-centos7 golang-centos7-app

Using the logic defined in the assemble script, s2i will now create an application image using the builder image as a base and including the source code from the test/test-app directory.

Running the application image

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

docker run -d -p 8080:8080 golang-centos7-app

The application, which consists of a simple static web page, should now be accessible at http://localhost:8080.

Using OpenShift

Create the builder image

The following command will create a builder image named golang-centos7.

$ oc new-build https://github.com/nmasse-itix/golang-s2i.git --name=golang-centos7
$ oc logs -f bc/golang-centos7

Creating and running the application image

The application image combines the builder image with your applications source code, which is served using whatever application is installed via the Dockerfile, compiled using the assemble script, and run using the run script. The following command will create the application image and run it:

$ oc new-app --strategy=source --context-dir=test/test-app --name golang-centos7-app golang-centos7~https://github.com/nmasse-itix/golang-s2i.git
$ oc logs -f bc/golang-centos7-app

Using the logic defined in the assemble script, s2i will now create an application image using the builder image as a base and including the source code from the test/test-app directory.

Creating a route for the application is needed to use it :

$ oc expose service golang-centos7-app
$ oc get route golang-centos7-app

The application, which consists of a simple static web page, should now be accessible at the url shown on last command (oc get route) :

$ curl "http://$(oc get route golang-centos7-app |awk '$1 == "golang-centos7-app" {print $2}')/"

Files and Directories

Dockerfile

Create a Dockerfile that installs all of the necessary tools and libraries that are needed to build and run our application. This file will also handle copying the s2i scripts into the created image.

S2I scripts

assemble

Create an assemble script that will build our application, e.g.:

• build python modules
• bundle install ruby gems
• setup application specific configuration

The script can also specify a way to restore any saved artifacts from the previous image.

run

Create a run script that will start the application.

save-artifacts (optional)

Create a save-artifacts script which allows a new build to reuse content from a previous version of the application image.

usage (optional)

Create a usage script that will print out instructions on how to use the image.

References

• https://blog.openshift.com/create-s2i-builder-image/
• https://docs.openshift.org/latest/creating_images/s2i.html