Pod disruption budget

A Pod Disruption Budget (PDB) allows you to limit the disruption to your application when its pods need to be rescheduled for some reason such as upgrades or routine maintenance work on the Kubernetes nodes.

Elastic Cloud on Kubernetes manages either a single default PDB, or multiple PDBs per Elasticsearch resource depending on the license level of the ECK installation.

In Elasticsearch clusters managed by ECK and licensed with an Enterprise license, PDBs are created based on Elasticsearch node roles, allowing Kubernetes upgrade or maintenance operations to be executed more quickly. Multiple nodeSets with the same roles, such as master or ml, are combined into a single PDB. Each PDB permits one Elasticsearch Pod to be disrupted at a time, provided the Elasticsearch cluster maintains the health status described in the following table.

Single-node clusters are not considered highly available and can always be disrupted regardless of license type.

In Elastic Cloud on Kubernetes clusters that do not have an Enterprise license, one Elasticsearch Pod can be taken down at a time, as long as the cluster has a health status of green. Single-node clusters are not considered highly available and can always be disrupted.

In the Elasticsearch specification, you can change the default behavior in two ways. By fully overriding the PodDisruptionBudget within the Elasticsearch spec or by disabling the default PodDisruptionBudget and specifying one or more PodDisruptionBudget(s).

You can fully override the default PodDisruptionBudget by specifying your own PodDisruptionBudget in the Elasticsearch spec.

apiVersion: elasticsearch.k8s.elastic.co/v1
kind: Elasticsearch
metadata:
  name: quickstart
spec:
  version: 9.5.6
  nodeSets:
  - name: default
    count: 3
  podDisruptionBudget:
    spec:
      minAvailable: 2
      selector:
        matchLabels:
          elasticsearch.k8s.elastic.co/cluster-name: quickstart

This will cause the ECK operator to only create the PodDisruptionBudget defined in the spec. It will not create any additional PodDisruptionBudgets.

You can specify a PDB per nodeSet or node role.

apiVersion: elasticsearch.k8s.elastic.co/v1
kind: Elasticsearch
metadata:
  name: quickstart
spec:
  podDisruptionBudget: {}
  version: 9.5.6
  nodeSets:
    - name: master
      count: 3
      config:
        node.roles: "master"
        node.store.allow_mmap: false
    - name: hot
      count: 2
      config:
        node.roles: ["data_hot", "data_content", "ingest"]
        node.store.allow_mmap: false

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: master-nodes-pdb
spec:
  minAvailable: 2
  selector:
    matchLabels:
      elasticsearch.k8s.elastic.co/cluster-name: quickstart
      elasticsearch.k8s.elastic.co/statefulset-name: quickstart-es-master

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: hot-nodes-pdb
spec:
  minAvailable: 1
  selector:
    matchLabels:
      elasticsearch.k8s.elastic.co/cluster-name: quickstart
      elasticsearch.k8s.elastic.co/statefulset-name: quickstart-es-hot

1. Disable the default Elasticsearch pod disruption budget.
2. Specify pod disruption budget to have 2 master nodes available.
3. The pods should be in the "quickstart" cluster.
4. Pod disruption budget applies on all master nodes.
5. Specify pod disruption budget to have 1 hot node available.
6. Pod disruption budget applies on nodes of the same nodeset.