Bouquet

Bouquet is a draft addon manager for the Gardener. It incorporates some of the requested features of the community but not yet all of them.

Caution: This software is early alpha. It is not meant for production use and shall (currently) only serve as a possible outlook of what is possible with pre-deployed software on Gardener Kubernetes clusters.

Installation

If you want to deploy Bouquet on a target Gardener cluster, run the following:

helm install charts/bouquet \
  --name gardener-bouquet \
  --namespace garden

This will deploy Bouquet with the required permissions into your garden cluster.

Structure

As of now, Bouquet comes with two new custom resources: AddonManifest and AddonInstance.

An AddonManifest can be considered equivalent to a Helm template. The manifest itself only contains metadata (like the name, default values etc.). The actual content of a manifest is specified via its source attribute. Currently, the only available source is a ConfigMap.

An AddonInstance references an AddonManifest and a target Shoot. It may also contain value overrides in its spec. As soon as an AddonInstance is created, Bouquet will apply the values to the templates and then ensure that the objects exist in the target shoot. If an AddonInstance is deleted, Bouquet will also make sure that the created objects are deleted as well.

Example use case

Say you want your cluster to contain istio right from the start. How can you do that?

First you need to get the .yaml files necessary to deploy istio into your cluster. Download an istio release as follows:

wget -O istio.yaml https://raw.githubusercontent.com/kubernetes/kubernetes/master/cluster/addons/istio/noauth/istio.yaml

This will fetch a .yaml file containing all necessary kubernetes objects of istio. To make this data available in your garden cluster, create a configmap in your cluster via

kubectl -n garden create configmap istio-files --from-file ./istio.yaml

Now you need to create an AddonManifest that references this file and push it to Kubernetes. The file could look like the following:

apiVersion: "garden.sapcloud.io/v1alpha1"
kind: "AddonManifest"
metadata:
  name: "istio-0.0.1"
  spec:
    configMap: "istio-files"

You can submit this manifest to Kubernetes via kubectl (given that you saved the file to addonmanifest.yaml:

kubectl -n garden apply -f addonmanifest.yaml

Once this is done, the only thing left to do is to create an AddonInstance referencing both your target Shoot and your AddonManifest. This AddonInstance has to be in the same namespace as your target Shoot:

apiVersion: "garden.sapcloud.io/v1alpha1"
kind: "AddonInstance"
metadata:
  name: "example"
  finalizers:
    - "bouquet"
spec:
  manifest:
    namespace: "garden"
    name: "istio"
    version: "0.0.1"
  target:
    shoot: "addon-test"

And apply it via kubectl (given that you saved the file to addoninstance.yaml):

kubectl -n garden-addon-test apply -f addoninstance.yaml

Bouquet will then start deploying your objects to the target Shoot once it is ready.

Outlook / Future

Since this is just a tech-preview, features like value / chart updates, more efficient templating, company addon guidelines etc. are not yet implemented / yet to come / yet to be discussed. It is also not yet clear whether this should eventually move into the Gardener or remain as a stand-alone component.

Core points that have to be tackled are:

• Fire and forget mode (only deploy objects once, don't monitor afterwards)
• Reconciliation (currently, updating behavior is not correctly implemented)
• Updates of an addon (-> Update strategies)
• Dependent addons / dependency resolution / dependency lifecycle

As such, contributions and help on shaping this topic is highly appreciated.