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scale-stateful-set.md

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{% capture overview %} This page shows how to scale a Stateful Set. {% endcapture %}

{% capture prerequisites %}

  • Stateful Sets are only available in Kubernetes release >= 1.5.
  • Stateful Sets are previously known as Pet Sets in Kubernetes release 1.3-1.4. You can either upgrade your Pet Sets to Stateful Sets, or just change all statefulset references to petset. TODO: link to upgrade from Pet Sets to Stateful Sets.
  • Not all stateful applications scale nicely. You need to understand your Stateful Sets well before continue. If you're unsure, remember that it may not be safe to scale your Stateful Sets.

{% endcapture %}

{% capture steps %}

Use kubectl to scale Stateful Sets

kubectl scale (>= 1.4 release)

First, find the Stateful Set you want to scale. Remember, you need to first understand if you can scale it or not.

kubectl get statefulsets <stateful-set-name>

If you wish to change the number of replicas of your Stateful Set, just use this command:

kubectl scale statefulsets <stateful-set-name> --replicas=<new-replicas>

Note that kubectl scale only works on Stateful Set with Kubernetes release >= 1.4.

Alternative: kubectl apply / kubectl edit / kubectl patch (>= 1.3 release)

Alternatively, you may do in-place updates on your Stateful Sets.

If your Stateful Set was initially created with kubectl apply or kubectl create --save-config, you may update .spec.replicas of the Stateful Set manifests, and then do a kubectl apply:

kubectl apply -f <stateful-set-file-updated>

Otherwise, you can just 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>}}'

Troubleshooting

Scaling down doesn't not work right

You cannot scale down a Stateful Set when some of the stateful pods it manages are unhealthy. Scaling down only takes place after those stateful pods become running and ready. See discussions here.

{% endcapture %}

{% capture whatsnext %} TODO: link to other docs about Stateful Set? {% endcapture %}

{% include templates/task.md %}