Ci cd introduction

-# Introduction

Nowadays agile software development methodologies are being used to satisfy the continuously changing requirements of a given software. The main aim of agile software development is to continuously and quickly deliver new pieces of software and improve customer satisfaction. Continuous Integration and Continuous Delivery (CI/CD) provides developers the necessary tools to streamline and accelerate the speed at which they can deploy new code and become more agile.

In this tutorial, we will set up a simple CI/CD pipeline using the Kubernetes concepts such as ImageStream, BuildConfig, and DeploymentConfig. Please refer to these Kubernetes concepts in Kubernetes and OpenShift concepts.

Info

In practice, CI/CD pipelines for complex applications involve the use of dedicated resources and tools such as Tekton and Jenkins. However, simple applications can be deployed the way described in this tutorial. The primary aim of this tutorial is to teach the core concepts of Kubernetes in terms of CI/CD.

Preparation

Make sure you have the oc command line installed, and that you are logged in. Please check the command line tool installation if you need help on that.

Quick Start

We have written a hello world web application and defined the necessary Kubernetes objects to build and deploy it to Rahti 2. The following steps will quickly get you started:

Clone the source repository for the sample application.

git clone https://github.com/CSCfi/rahti-bc-example.git
cd rahti-bc-example/

Login to Rahti 2 if you haven't done so. You can copy your login command from the Rahti 2 UI.

 oc login https://api.2.rahti.csc.fi:6443 --token=<your_token>

Make sure you are in the right project with oc project and if not you can create one with oc new-project <your-new-project-name>.

We have all the necessary object definitions in the rahti-bc-example project under the k8s-api-objs.yaml. Please refer to Kubernetes and OpenShift concepts to understand the objects defined under k8s-api-objs.yaml. You can easily create these objects necessary for our CI/CD pipeline using the oc create command as follows:

$ oc create -f k8s-api-objs.yaml
imagestream.image.openshift.io/dockerfile-example created
buildconfig.build.openshift.io/dockerfile-example created
deploymentconfig.apps.openshift.io/dockerfile-example created
service/dockerfile-example created
route.route.openshift.io/dockerfile-example created

At this point you have a simple CI\CD pipeline created. The next step will be to kick off the build and let the pipeline handle the build and deployment. You can trigger such an action using the oc build as follows:

oc start-build dockerfile-example --from-dir=./ -F

Once the pipeline finishes running you can visit your application deployment by following the route which should look like http://dockerfile-example-<your_project_name>.2.rahtiapp.fi/. This pipeline can be triggered again after any update to your application (e.g. update on index.html) and the changes would reflect almost immediately. Webhooks can also be setup to trigger the pipeline.

Cleaning up

Once we are satisfied with the application, let us not keep it running in the cluster but remove it with the command oc delete:

oc delete all --selector app=dockerfile-example

This will delete all objects with the label app: dockerfile-example.

Conclusion

In this tutorial, a simple CI/CD pipeline to build and deploy a static web page was created mainly using the Kubernetes objects ImageStream, BuildConfig, and DeploymentConfig. The pipeline can be further extended using dedicated tools and resources as Jenkins, Tekton, and Webhooks.

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