Skip to content

Latest commit

 

History

History
59 lines (41 loc) · 4.81 KB

controller-manager.md

File metadata and controls

59 lines (41 loc) · 4.81 KB
Raw

Gardener Controller Manager

The Gardener Controller Manager (often refered to as "GCM") is a component that runs next to the Gardener API server, similar to the Kubernetes Controller Manager. It runs several control loops that do not require talking to any seed or shoot cluster. Also, as of today it exposes a HTTPS server that is serving several endpoints for webhooks for certain resources.

This document explains the various functionalities of the Gardener Controller Manager and their purpose.

Control Loops

Project Controller

This controller consists out of two reconciliation loops: The main loop is reconciling Project resources while the second loop is controlling the necessary actions for stale projects.

"Main" Reconciler

This reconciler will create a dedicated Namespace prefixed with garden- for each Project resource. The name of the namespace can either be stated in the .spec.namespace, or it will be auto-generated by the reconciler. If .spec.namespace is set then it creates it if it does not exist yet. Otherwise, it tries to adopt it. This will only succeed if the Namespace was previously labeled with gardener.cloud/role=project and project.gardener.cloud/name=<project-name>. This is to prevent that end-users can adopt arbitrary namespaces and escalate their privileges, e.g. the kube-system namespace.

After the namespace was created/adopted the reconciler creates several ClusterRoles and ClusterRoleBindings that allow the project members to access related resources based on their roles. These RBAC resources are prefixed with gardener.cloud:system:project{-member,-viewer}:<project-name>. Gardener administrators and extension developers can define their own roles, see this document for more information.

The .status.phase of the Project resources will be set to Ready or Failed by the reconciler to indicate whether the reconciliation loop was performed successfully. Also, it will generate Events to provide further information about its operations.

"Stale Projects" Reconciler

As Gardener is a large-scale Kubernetes as a Service it is designed for being used by a large amount of end-users. Over time, it is likely to happen that some of the hundreds or thousands of Project resources are no longer actively used.

Gardener offers the "stale projects" reconciler which will take care of identifying such stale projects, marking them with a "warning", and eventually deleting them after a certain time period. This reconciler is enabled by default and works as following:

  1. Projects are considered as "stale"/not actively used when all of the following conditions apply: The namespace associated with the Project does not have any...
    1. Shoot resources.
    2. Plant resources.
    3. BackupEntry resources.
    4. Secret resources that are referenced by a SecretBinding that is in use by a Shoot (not necessarily in the same namespace).
    5. Quota resources that are referenced by a SecretBinding that is in use by a Shoot (not necessarily in the same namespace).

If a project is considered "stale" then its .status.staleSinceTimestamp will be set to the time when it was first detected to be stale. If it gets actively used again this timestamp will be removed. After some time the .status.staleAutoDeleteTimestamp will be set to a timestamp after which Gardener will auto-delete the Project resource if it still is not actively used.

The component configuration of the Gardener Controller Manager offers to configure the following options:

  • minimumLifetimeDays: Don't consider newly created Projects as "stale" too early to give people/end-users some time to onboard and get familiar with the system. The "stale project" reconciler won't set any timestamp for Projects younger than minimumLifetimeDays. When you change this value then projects marked as "stale" may be no longer marked as "stale" in case they are young enough, or vice versa.
  • staleGracePeriodDays: Don't compute auto-delete timestamps for stale Projects that are unused for only less than staleGracePeriodDays. This is to not unnecessarily make people/end-users nervous "just because" they haven't actively used their Project for a given amount of time. When you change this value then already assigned auto-delete timestamps may be removed again if the new grace period is not yet exceeded.
  • staleExpirationTimeDays: Expiration time after which stale Projects are finally auto-deleted (after .status.staleSinceTimestamp). If this value is changed and an auto-delete timestamp got already assigned to the projects then the new value will only take effect if it's increased. Hence, decreasing the staleExpirationTimeDays will not decrease already assigned auto-delete timestamps.

Webhooks

ℹ️ This document is incomplete and under construction.