+++ dep = 9 title = "Alternative Container Image Builders" authors = [ "Matt Fisher [email protected]" ] created = 2018-04-23 +++
This document outlines the general design principles around providing alternative container image builders to Draft.
A Container Image Builder is a tool that builds a container image. A container image is a stand-alone executable package of a piece of software that includes everything needed to run it: code, runtime, system tools, system libraries, and settings.
Draft is a CLI tool built around building container images and running them on Kubernetes, providing the "inner loop" of a developer's workflow with running container images on Kubernetes.
The Draft client interfaces with a container image builder much like how it interacts with Tiller.
Container image builders can be configured either through draft.toml or through draft config set container-builder mycontainerbuilder.
When draft up is invoked, the configured container image builder is invoked, building the image and pushing it to the container registry configured via draft config set registry. It also provides a mechanism to retrieve an auth token for the Kubernetes cluster to fetch that image.
As an example, the default Docker container image builder performs the following:
- logs into the container registry with
docker login - builds the container image using
docker build - pushes the image to the container registry using
docker push - creates an
imagePullSecretso Kubernetes can pull down the image from the container registry
In its current form, all container image builders are part of Draft and configured through draft config. It would be useful in future iterations to break this apart into a Bridge pattern, such that each of these container builders can be shipped separately as add-ons for Draft, enabling users to try out different container builders while ensuring Draft's core to remain stable.