k8s.io/kubernetes@v1.31.0-alpha.0.0.20240520171757-56147500dadc/cluster/addons/README.md (about)

     1  # Legacy Cluster add-ons
     2  
     3  For more information on add-ons see [the documentation](https://kubernetes.io/docs/concepts/cluster-administration/addons/).
     4  
     5  ## Overview
     6  
     7  Cluster add-ons are resources like Services and Deployments (with pods) that are
     8  shipped with the Kubernetes binaries and are considered an inherent part of the
     9  Kubernetes clusters.
    10  
    11  There are currently two classes of add-ons:
    12  - Add-ons that will be reconciled.
    13  - Add-ons that will be created if they don't exist.
    14  
    15  More details could be found in [addon-manager/README.md](addon-manager/README.md).
    16  
    17  ## Cooperating Horizontal / Vertical Auto-Scaling with "reconcile class addons"
    18  
    19  "Reconcile" class addons will be periodically reconciled to the original state given
    20  by the initial config. In order to make Horizontal / Vertical Auto-scaling functional,
    21  the related fields in config should be left unset. More specifically, leave `replicas`
    22  in `ReplicationController` / `Deployment` / `ReplicaSet` unset for Horizontal Scaling,
    23  leave `resources` for container unset for Vertical Scaling. The periodic reconcile
    24  won't clobbered these fields, hence they could be managed by Horizontal / Vertical
    25  Auto-scaler.
    26  
    27  ## Add-on naming
    28  
    29  The suggested naming for most of the resources is `<basename>` (with no version number).
    30  Though resources like `Pod`, `ReplicationController` and `DaemonSet` are exceptional.
    31  It would be hard to update `Pod` because many fields in `Pod` are immutable. For
    32  `ReplicationController` and `DaemonSet`, in-place update may not trigger the underlying
    33  pods to be re-created. You probably need to change their names during update to trigger
    34  a complete deletion and creation.