krane

krane is a tool to render kubernetes manifests using a simple structure of templates and configuration.

A sample structure could be something like:

KRANE_ROOT
├── config
│   ├── clusters
│   │   ├── cluster01.yml
│   │   └── cluster02.yml
│   ├── config.yml
│   ├── production.yml
│   └── staging.yml
├── manifests
├── templates

Configuration files

All configuration is described using yaml.

config.yml

This file has two keys, fleets and globals, and it's mandatory.

fleets

This key describes the grouping of clusters we choose to use.

This could be the typical staging, production environments, could be clusters living in separate cloud provider accounts, or clusters running workloads for different teams.

globals

This key will hold values common to all fleets.

fleet.yml

This file will hold the values to be used by all clusters in that fleet. Each defined fleet must have a configuration file with its name.

Here you can also use the special key Secrets to hold all values that will be base64 encoded before being rendered into the secret templates that reference it.

cluster.yml

This file will hold the overrides to be used in a particular cluster. This file is optional.

Here you can also use the special key Exclude that holds a list of strings that will be matched against the path of templates being rendered and determine which templates should be ruled out.

Rendering process

The tool will look in a determined path for template files. That path will be traversed and all .yaml or .yml files loaded. The found structure will be maintained for each of the clusters, meaning that the structure of the templates folder will detemine the structure of the final manifests folder.

Steps

1. Wipe out the manifests folder to start from a clean slate
   • If the manifests are in a git repository this allows git diff to easily show us any changes introduced
2. Load all templates into memory
3. Load all configuration, merging globals and overides into each cluster configuration
4. Loop clusters, rendering the templates and appending the names of both Secrets and ConfigMaps with a hash based on their contents
5. Update all manifests that reference those Secrets and ConfigMaps
6. Write all manifests

Building

• make or make build will build the docker image krane

Testing

• make unit-test will build a docker image named tests/krane that will run all unit tests
• make test will run the krane image with CI=true which will render manifests in the tests folder

Running

krane will run on the directory where is called, provided it's in the PATH.

If the actual structure exists elsewhere, please provide it's location via KRANE_ROOT environment variable.