„If it is not in GitOps, it does not exist“ - However, managing objects partially only by Gitops was always an issue, since ArgoCD would like to manage the whole object. For example, when you tried to work with node labels and would like to manage them via Gitops, you would need to put the whole node object into ArgoCD. This is impractical since the node object is very complex and typically managed by the cluster.
There were 3rd party solutions (like the patch operator), that helped with this issue.
However, with the Kubernetes feature Server-Side Apply this problem is solved. Read further to see a working example of this feature.
Server-Side Apply helps users and controllers manage their resources through declarative configurations. Clients can create and modify their objects declaratively by sending their fully specified intent.
A fully specified intent is a partial object that only includes the fields and values for which the user has an opinion. That intent either creates a new object or is combined, by the server, with the existing object.
In other words: you can send a snippet of an object to the cluster and the cluster will eventually combine everything on the server and not validate on the client side first. All you need is a way to identify the object. Usually, the name and maybe the namespace too.
SSA and ArgoCD
When it comes to GitOps the implementation of SSA is quite new. However, it is important to note, that (managed field) conflicts are currently not handled by ArgoCD. Instead, ArgoCD forces a change and overrides everything, even if the field is managed by somebody else. This might be improved in the future. Nevertheless … let’s test the feature.
The support of the Server-Side Apply feature is currently available in the latest version of ArgoCD. This means, that the channel of the openshift-gitops operator must be changed to "latest", which will deploy openshift-gitops version 1.6
A new stable version will arrive soon. :)
Node Labelling Chart
In this example, I would like to use a Helm chart that will try to set two different labels on 2 nodes. This is a very easy example to demonstrate the feature.
This is not a full definition of a Node object. The only things defined are the node name and the labels. (Besides the customer labels we would like to add, some default labels are added automatically.)
So we have a Helm chart in Git. Perfect, but to automate everything with Gitops we need to create the object Application. For example the following: