Building Docker images with Buildpacks and Gitlab CI
This blog is second in the Cloud Native Buildpack(CNB) series, If you are new to CNB, refer to previous Introduction blog Introduction to Cloud Native Buildpacks with Kubernetes.
Buildpacks enable us to create a OCI compatible Docker image from application source code, which we can consume very easily using pack cli.
Buildpacks are now part of open source CNCF Buildpacks project.
We can use pack cli to create our Docker images, without even writing a Dockerfile.
For testing we can do it manually, but for actual production deployment, we need CI pipeline for the job.
In this blog you will be creating a CI pipeline using Gitlab, which will use CNB and final image will be pushed to Docker hub.
Prerequisites
- Gitlab account under free plan, create one using the Gitlab Register link.
- Docker hub account, create one using Docker Hub signup page.
Creating CI pipeline in Gitlab
Once you have your Gitlab account, sign in and Fork this repositoryhttps://gitlab.com/ronakbanka.cse/cnb-go
Once we have forked the repo, next step is to set the environment variables for Docker hub account in repository settings.
Go to Settings and under Settings go to CI/CD
Once we are into CI/CI settings, we can see Variables section to Expand
We will be adding 2 variables here DOCKER_HUB_USER & DOCKER_HUB_PASSWORD, which are your Docker hub credentials, and enable masking, so no credentials are visible during Job execution, click on Save variables.
In repository there is a file .gitlab-ci.yml.sample which is similar to actual ci file, once we change the name to.gitlab-ci.yml, it will automatically create a pipeline for us
Click on .gitlab-ci.yml.sample file in git repository, click on Edit button in blue, and in edit mode change the file name to .gitlab-ci.yml, click on Commit changes!
Now are pipeline is in place, let’s check our pipeline in CI/CD panel on Gitlab
In pipelines dashboard, we should be able to see our pipeline run status, which was triggered as soon as we committed the gitlab-ci file in our repository.
To check the pipeline run , click either on status or pipeline number, here it is #109397950.
Our pipeline will show the stages and Jobs, lets click on job which build_and_push_image, which will take us to the actual run
Once your Job is successful, you can see newly pushed docker image in your Docker hub account.
Voila!! We have Continuous integration pipeline with Gitlab source repo and Cloud native buildpacks!!
Deep Dive on Gitlab CI configuration file
image: docker:stable
variables:
DOCKER_DRIVER: overlay2
REALM: shared
DOCKER_HOST: tcp://docker:2375/
services:
- name: docker:dind
entrypoint: ["env", "-u", "DOCKER_HOST"]
command: ["dockerd-entrypoint.sh"]
stages:
- build
build_and_push_image:
stage: build
before_script:
- wget https://github.com/buildpacks/pack/releases/download/v0.6.0/pack-v0.6.0-linux.tgz
- tar xvf pack-v0.6.0-linux.tgz
- rm pack-v0.6.0-linux.tgz
script:
- echo "$DOCKER_HUB_PASSWORD" | docker login --username "$DOCKER_HUB_USER" --password-stdin
- ./pack build "$DOCKER_HUB_USER"/cnb-goapp --builder gcr.io/paketo-buildpacks/builder:base --publish
We have used docker:stable as runtime image, so that we can use docker cli to login to Docker hub
docker:dind is docker in docker service which is used during runtime.
