The garbage collector (GC) cascadingly deletes dependent API objects when the owner is deleted. One use case is if two objects have functional dependency, you can specify the dependency in their configuration file when creating them, and if one of them is deleted, the GC will delete the other one automatically. The other use case is if there is logical dependency among API objects, e.g., the pods created by a replicaset depending on the replicaset, Kubernetes will automatically set the dependency (this will be implemented in release 1.4) and the GC will delete the pods when the replicaset is deleted.
In release 1.3, there is a new
ownerReferences field in the
metadata of every Kubernetes API objects. The GC monitors the cluster and checks the
metadata.ownerReferences field of each object. If none of the owners present in
metadata.ownerReferences exists in the cluster, the GC will request the API server to delete the object.
Currently a user needs to manually set the
metadata.ownerReferences. In release 1.4, controllers will automatically set the field for the objects it controls. For example, when the replicaset controller creates or adopts pods, it will automatically add the replicaset to the
metadata.ownerReferences fields of the pods.
When deleting an object, you can prevent the GC from deleting that object’s dependents by specifying
deleteOptions.orphanDependents=true in the deletion request. It prevents garbage collection by removing the object from its dependents’ metadata.ownerReferences field.
The garbage collector is an alpha feature so it is disabled by default. To enable it, you need to start the kube-apiserver and kube-controller-manager with flag