Implementation¶

The project uses kubebuilder tool to scaffold new controllers and types.
Before deciding on kubebuilder, opsdk was considered but kubebuilder is more active and has better documentation. Moreover, it has better support for webhooks. Also, there is an effort underway to integrate these two projects as far as Go operators are concerned.

More details about the implementation will be added soon.

Status updates¶

By default, any updates to status of a resource results in reconciling. This is a problem if status is being updated in the controller and might result in infinite loop of update followed by a reconcile. In many cases, you just want to update the status and don’t want to have to process that update again.

One way to achieve that is by checking to see if the “generation” number of a resource changed. This number is bumped up only if the “spec” of a resource changes. So if we skip reconcile in case the “generation” number hasn’t changed, we will be avoiding reconciles triggered by status updates. But keep in mind that you may miss other changes to the metadata (such as changes to annotations) as well.

To implement this technique, do the following (using backupLoc as the resource in the examples below):

Add the following field to the status struct:

// +kubebuilder:validation:Optional
ObservedGeneration int64 `json:"observedGeneration"`

Set the generation number in status (do this whether or not the current operation succeeds).
```
backupLoc.Status.ObservedGeneration = backupLoc.ObjectMeta.Generation
```

Do the following check in the relevant controller:

if backupLoc.Status.ObservedGeneration == backupLoc.ObjectMeta.Generation {
    return ctrl.Result{}, nil
}