Black lives matter.
We stand in solidarity with the Black community.
Racism is unacceptable.
It conflicts with the core values of the Kubernetes project and our community does not tolerate it.
We stand in solidarity with the Black community.
Racism is unacceptable.
It conflicts with the core values of the Kubernetes project and our community does not tolerate it.
This task shows how to scale a StatefulSet. Scaling a StatefulSet refers to increasing or decreasing the number of replicas.
StatefulSets are only available in Kubernetes version 1.5 or later.
To check your version of Kubernetes, run kubectl version
.
Not all stateful applications scale nicely. If you are unsure about whether to scale your StatefulSets, see StatefulSet concepts or StatefulSet tutorial for further information.
You should perform scaling only when you are confident that your stateful application cluster is completely healthy.
First, find the StatefulSet you want to scale.
kubectl get statefulsets <stateful-set-name>
Change the number of replicas of your StatefulSet:
kubectl scale statefulsets <stateful-set-name> --replicas=<new-replicas>
Alternatively, you can do in-place updates on your StatefulSets.
If your StatefulSet was initially created with kubectl apply
,
update .spec.replicas
of the StatefulSet manifests, and then do a kubectl apply
:
kubectl apply -f <stateful-set-file-updated>
Otherwise, edit that field with kubectl edit
:
kubectl edit statefulsets <stateful-set-name>
Or use kubectl patch
:
kubectl patch statefulsets <stateful-set-name> -p '{"spec":{"replicas":<new-replicas>}}'
You cannot scale down a StatefulSet when any of the stateful Pods it manages is unhealthy. Scaling down only takes place after those stateful Pods become running and ready.
If spec.replicas > 1, Kubernetes cannot determine the reason for an unhealthy Pod. It might be the result of a permanent fault or of a transient fault. A transient fault can be caused by a restart required by upgrading or maintenance.
If the Pod is unhealthy due to a permanent fault, scaling without correcting the fault may lead to a state where the StatefulSet membership drops below a certain minimum number of replicas that are needed to function correctly. This may cause your StatefulSet to become unavailable.
If the Pod is unhealthy due to a transient fault and the Pod might become available again, the transient error may interfere with your scale-up or scale-down operation. Some distributed databases have issues when nodes join and leave at the same time. It is better to reason about scaling operations at the application level in these cases, and perform scaling only when you are sure that your stateful application cluster is completely healthy.