graylog pods are unavailable during cluster upgrade

[pparthesh]

Describe the bug

cluster upgrade evict multiple pods from multiple nodes and without PodDisruptionBudget possible to evict all graylog pods from different nodes.

Version of Helm and Kubernetes:

Helm Version:

$ helm version
version.BuildInfo{Version:"v3.11.2", GitCommit:"v3.11.2", GitTreeState:"", GoVersion:"go1.20.3"}

Kubernetes Version:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.0",
Server Version: version.Info{Major:"1", Minor:"26", GitVersion:"v1.26.3", 

Which version of the chart: 2.3.2

What happened:

node rotation during cluster upgrade evicted all graylog pods and faced downtime.

What you expected to happen:

one graylog pod evict during cluster upgrade.

How to reproduce it (as minimally and precisely as possible):

create separate node group for graylog and deploy graylog on that node group using taint/tolerations and try to upgrade nodes.

Solution:

poddisruptionbudget.yaml

{{- if .Values.podDisruptionBudget }}
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: {{ template "graylog.fullname" . }}
  labels:
{{ include "graylog.metadataLabels" . | indent 4 }}
spec:
  {{- with .Values.podDisruptionBudget.minAvailable }}
  minAvailable: {{ . }}
  {{- end }}
  {{- with .Values.podDisruptionBudget.maxUnavailable }}
  maxUnavailable: {{ . }}
  {{- end }}
  selector:
    matchLabels:
      app.kubernetes.io/name: {{ template "graylog.name" . }}
      app.kubernetes.io/instance: "{{ .Release.Name }}"
{{- end }}

values.yaml

## See `kubectl explain poddisruptionbudget.spec` for more
## ref: https://kubernetes.io/docs/tasks/run-application/configure-pdb/
podDisruptionBudget: {}
#  minAvailable: 1
#  maxUnavailable: 1