katenary/doc/docs/usage.md

Basic Usage

Basically, you can use katenary to transpose a docker-compose file (or any compose file compatible with podman-compose and docker-compose) to a configurable Helm Chart. This resulting helm chart can be installed with helm command to your Kubernetes cluster.

Katenary transforms compose services this way:

• Takes the service and create a "Deployment" file
• if a port is declared, katenary creates a service (ClusterIP)
• it a port is exposed, katenary creates a service (NodePort)
• environment variables will be stored in values.yaml file
• image, tags, and ingresses configuration are also stored in values.yaml file
• if named volumes are declared, katenary create PersistentVolumeClaims - not enabled in values file (a emptyDir is used by default)
• any other volume (local mount points) are ignored
• depends_on needs that the pointed service declared a port. If not, you can use labels to inform katenary

Katenary can also configure containers grouping in pods, declare dependencies, ignore some services, force variables as secrets, mount files as configMap, and many others things. To adapt the helm chart generation, you will need to use some specific labels.

Try to convert

After having installed katenary, the standard usage is to call:

katenary convert

It will search standard compose files in the current directory and try to create a helm chart in "chart" directory.

Katenary respects the Docker rules for overrides files, and you can of course force others files:

katenary convert -c file1.yaml -c file2.yaml

Work with Depends On?

Kubernetes does not propose service or pod starting detection from others pods. But katenary will create init containers to make you able to wait for a service to respond. But you'll probably need to adapt a bit the compose file.

See this compose file:

version: "3"

services:
    webapp:
        image: php:8-apache
        depends_on:
        - database

    database:
        image: mariadb
        environment:
            MYSQL_ROOT_PASSWORD: foobar

In this case, webapp needs to know the database port because the depends_on points on it and Kubernetes has not (yet) solution to check the database startup. Katenary wants to create a initContainer to hit on the related service. So, instead of exposing the port in the compose definition, let's declare this to katenary with labels:

version: "3"

services:
    webapp:
        image: php:8-apache
        depends_on:
        - database

    database:
        image: mariadb
        environment:
            MYSQL_ROOT_PASSWORD: foobar
        labels:
            katenary.io/ports: 3306