Katenary is a tool to help transforming docker-compose files to a working Helm Chart for Kubernetes.

Install

If you've got podman or docker, you can build katenary by using:

make build

You can then install it with:

make install

It will use the default PREFIX (~/.local/) to install the binary in the bin subdirectory. You can force the PREFIX value at install time, but maybe you need to use "sudo":

sudo make install PREFIX=/usr/local

Usage

Usage of katenary:
  -appname string
    	Give the helm chart app name (default "MyApp")
  -appversion string
    	Set the chart appVersion (default "0.1.1")
  -compose string
    	set the compose file to parse (default "docker-compose.yaml")
  -version
    	Show version and exist

Katenary will try to find a docker-compose.yaml file inside the current directory. It will then delete the chart directory to create a new Helm Chart.

It's important that you keep in mind that katenary will not alert you (for now) that it will remove the chart directory !

It creates a subdirectory inside chart that is named with the appname option (default is MyApp)

What can be interpreted by Katenary:

• Services with "image" section (cannot work with "build" section)
• Named Volumes are transformed to persistent volume claims - note that local volume will break the transformation to Helm Chart because there is (for now) no way to make it working (see below for resolution)
• if ports and/or expose section, katenary will create Services and bind the port to the corresponding container port
• depends_on will add init containers to wait for the depending service (using the first port)
• some labels can help to bind values:
  • katernay.io/expose-ingress: true will expose the first port or expose to an ingress
  • katernay.io/to-service: VARNAME will convert the value to a variable {{ .Release.Name }}-VARNAME - it's usefull when you want to pass the name of a service as a variable (think about the service name for mysql to pass to a container that wants to connect to this)

Exemple of a possible docker-compose.yaml file:

version: "3"
services:
    webapp:
        image: php:7-apache
        environment:
            # note that "database" is a service name
            DB_HOST: database
        expose:
            - 80
        depends_on:
            # this will create a init container waiting for 3306 port
            # because it's the "exposed" port
            - database
        labels:
            # explain to katenary that "DB_HOST" value is variable (using release name)
            katernay.io/to-servie: DB_HOST
    database:
        image: mariabd:10
        environment:
            MARIADB_ROOT_PASSWORD: foobar
        expose:
            # required to make katenary able to create the init container
            - 3306