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.
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.
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 ClusterRole
s and ClusterRoleBinding
s 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 Event
s to provide further information about its operations.
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:
- 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...Shoot
resources.Plant
resources.BackupEntry
resources.Secret
resources that are referenced by aSecretBinding
that is in use by aShoot
(not necessarily in the same namespace).Quota
resources that are referenced by aSecretBinding
that is in use by aShoot
(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 createdProject
s 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 forProject
s younger thanminimumLifetimeDays
. 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 staleProject
s that are unused for only less thanstaleGracePeriodDays
. This is to not unnecessarily make people/end-users nervous "just because" they haven't actively used theirProject
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 staleProject
s 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 thestaleExpirationTimeDays
will not decrease already assigned auto-delete timestamps.
With the Gardener Event Controller you can prolong the lifespan of events related to Shoot clusters. This is an optional controller which will become active once you provide the below mentioned configuration.
All events in K8s are deleted after a configurable time-to-live (controlled via a kube-apiserver argument called --event-ttl
(defaulting to 1 hour)).
The need to prolong the time-to-live for Shoot cluster events frequently arises when debugging customer issues on live systems.
This controller leaves events involving Shoots untouched while deleting all other events after a configured time.
In order to activate it, provide the following configuration:
concurrentSyncs
: The amount of goroutines scheduled for reconciling events.ttlNonShootEvents
: When an event reaches this time-to-live it gets deleted unless it is a Shoot-related event (defaults to1h
, equivalent to theevent-ttl
default).
⚠️ In addition, you should also configure the--event-ttl
for the kube-apiserver to define an upper-limit of how long Shoot-related events should be stored. The--event-ttl
should be larger than thettlNonShootEvents
or this controller will have no effect.
ℹ️ This document is incomplete and under construction.