Check whether required params for embedded addons are present

[judge-red]

What happened:

Here's a snippet from my KubeOneCluster manifest:

apiVersion: kubeone.io/v1beta1
kind: KubeOneCluster
addons:
    enable: true
    path: ./addons
    addons:
        - name: cluster-autoscaler
versions:

As you can see, I missed to configure the AUTOSCALER_VERSION param.

After applying this, I saw this funny issue:

  Warning  InspectFailed  3m53s (x558 over 124m)  kubelet            Failed to apply default image tag "k8s.gcr.io/autoscaling/cluster-autoscaler:${AUTOSCALER_VERSION}": couldn't parse image reference "k8s.gcr.io/autoscaling/cluster-autoscaler:${AUTOSCALER_VERSION}": invalid reference format

What is the expected behavior:

kubeone should probably fail before deploying addons, if required parameters are missing.

How to reproduce the issue:

See above - install e.g. the embedded cluster-autoscaler addon but don't specify any params.

Anything else we need to know?

Better examples wrt enabling the embedded addons would be nice.

Information about the environment:
KubeOne version (kubeone version): 1.3

[xmudrii]

In this concrete case, we fixed this bug for the cluster-autoscaler addon yesterday with #1552. The version is now determined automatically based on the Kubernetes version, but it can also be overridden if needed (see the description of #1552 for more details). The fix will be included in the upcoming 1.3.1 patch release, but the release date is still TBD.

However, this might still be the issue for other addons, so I'm going to leave this issue open until we don't check and eventually fix other addons.

[judge-red]

Thanks for the quick response @xmudrii! That's great news, looking forward to 1.3.1 :)

[judge-red]

@xmudrii It's been a while and I also see other important fixes have been backported to 1.3. Do you think we could get a new release in the near future? :)

[xmudrii]

@judge-red We are waiting for #1607 which should be merged soon. I hope we will be able to cut 1.3.1 beginning of next week.

[kron4eg]

I don't even know how it can be possibly done in generic way. Go templates are absolutely happy to consume nils.

The best workaround I see is to define a "required" template function, that will ensure not-nilness of the given argument, and would fail the template render otherwise. Of course its usage should be explicit.

[kron4eg]

helm has "required" function like this:

https://github.com/helm/helm/blob/b6a04cfbd544f0bbeea449129c1497eec8d99e2b/pkg/engine/engine.go#L155-L174