feat: support existing persistent volume (apache#105)

Statefulset `volumeClaimTemplates` create new volumes and `PersistentVolumeClaims` which cannot be mutated. This adds the ability to declare a `persistentVolume` as existing and provide the required PV and PVC data for binding a volume to the statefulset. This is especially useful for restoring backup snapshots during disaster recovery efforts, but could also be used for initial data migrations or other scenarios where users would like to deploy this chart with existing CouchDB data.

.gitignore

@@ -0,0 +1 @@
+*.swp

couchdb/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v1
 name: couchdb
-version: 4.1.1
+version: 4.2.0
 appVersion: 3.2.1
 description: A database featuring seamless multi-master sync, that scales from
   big data to mobile, with an intuitive HTTP/JSON API and designed for

couchdb/templates/_helpers.tpl

@@ -64,8 +64,6 @@ using `lookup` and `get`. The "key", "ns", and "secretName" keys need to be prov
   {{- end -}}
 {{- end -}}
 
-
-
 {{/*
 Labels used to define Pods in the CouchDB statefulset
 */}}
@@ -102,3 +100,46 @@ Fail if couchdbConfig.couchdb.uuid is undefined
 {{- define "couchdb.uuid" -}}
 {{- required "A value for couchdbConfig.couchdb.uuid must be set" (.Values.couchdbConfig.couchdb | default dict).uuid -}}
 {{- end -}}
+
+{{/*
+Repurpose volume claim metadata whether using the new volume claim template
+or existing volume claims.
+*/}}
+{{- define "persistentVolume.metadata" -}}
+{{- $context := index . "context" -}}
+{{- $claim := index . "claim" -}}
+name: {{ $claim.claimName | default "database-storage" }}
+labels:
+  app: {{ template "couchdb.name" $context }}
+  release: {{ $context.Release.Name }}
+{{- with $context.Values.persistentVolume.annotations }}
+annotations:
+  {{- toYaml . | nindent 6 }}
+{{- end }}
+{{- end -}}
+
+{{/*
+Repurpose volume claim spec whether using the new volume claim template
+or an existing volume claim.
+*/}}
+{{- define "persistentVolume.spec" -}}
+{{- $context := index . "context" -}}
+{{- $claim := index . "claim" -}}
+accessModes:
+{{- range $context.Values.persistentVolume.accessModes }}
+- {{ . | quote }}
+{{- end }}
+resources:
+  requests:
+    storage: {{ $context.Values.persistentVolume.size | quote }}
+{{- if $context.Values.persistentVolume.storageClass }}
+{{- if (eq "-" $context.Values.persistentVolume.storageClass) }}
+storageClassName: ""
+{{- else }}
+storageClassName: "{{ $context.Values.persistentVolume.storageClass }}"
+{{- end }}
+{{- end }}
+{{- if $claim.persistentVolumeName }}
+volumeName: {{ $claim.persistentVolumeName }}
+{{- end }}
+{{- end -}}

couchdb/templates/persistentvolume.yaml

@@ -0,0 +1,24 @@
+{{- if and .Values.persistentVolume.enabled .Values.persistentVolume.existingClaims -}}
+{{- range $claim := .Values.persistentVolume.existingClaims }}
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: {{ $claim.persistentVolumeName }}
+spec:
+{{- if $.Values.persistentVolume.storageClass }}
+{{- if (eq "-" $.Values.persistentVolume.storageClass) }}
+  storageClassName: ""
+{{- else }}
+  storageClassName: "{{ $.Values.persistentVolume.storageClass }}"
+{{- end }}
+{{- end }}
+  accessModes:
+  {{- range $.Values.persistentVolume.accessModes }}
+    - {{ . | quote }}
+  {{- end }}
+  capacity:
+    storage: {{ $.Values.persistentVolume.size }}
+{{ toYaml $claim.volumeSource | indent 2 }}
+---
+{{- end }}
+{{- end }}

couchdb/templates/persistentvolumeclaim.yaml

@@ -0,0 +1,12 @@
+{{- if and .Values.persistentVolume.enabled .Values.persistentVolume.existingClaims -}}
+{{- $context := . }}
+{{- range $claim := .Values.persistentVolume.existingClaims }}
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  {{- include "persistentVolume.metadata" (dict "context" $context "claim" $claim) | nindent 2 }}
+spec:
+  {{- include "persistentVolume.spec" (dict "context" $context "claim" $claim) | nindent 2 }}
+---
+{{- end }}
+{{- end }}

couchdb/templates/statefulset.yaml

@@ -207,30 +207,16 @@ spec:
 {{- if not .Values.persistentVolume.enabled }}
         - name: database-storage
           emptyDir: {}
+{{- else if and .Values.persistentVolume.enabled .Values.persistentVolume.existingClaims }}
+        {{- range $claim := .Values.persistentVolume.existingClaims }}
+        - name: {{ $claim.volumeName }}
+          persistentVolumeClaim:
+            claimName: {{ $claim.claimName }}
+        {{- end }}
 {{- else }}
   volumeClaimTemplates:
     - metadata:
-        name: database-storage
-        labels:
-          app: {{ template "couchdb.name" . }}
-          release: {{ .Release.Name }}
-        {{- with .Values.persistentVolume.annotations }}
-        annotations:
-          {{- toYaml . | nindent 10 }}
-        {{- end }}
+        {{- include "persistentVolume.metadata" (dict "context" .) | nindent 8 }}
       spec:
-        accessModes:
-        {{- range .Values.persistentVolume.accessModes }}
-          - {{ . | quote }}
-        {{- end }}
-        resources:
-          requests:
-            storage: {{ .Values.persistentVolume.size | quote }}
-      {{- if .Values.persistentVolume.storageClass }}
-      {{- if (eq "-" .Values.persistentVolume.storageClass) }}
-        storageClassName: ""
-      {{- else }}
-        storageClassName: "{{ .Values.persistentVolume.storageClass }}"
-      {{- end }}
-      {{- end }}
+        {{- include "persistentVolume.spec" (dict "context" .) | nindent 8 }}
 {{- end }}

couchdb/values.yaml

@@ -67,6 +67,8 @@ serviceAccount:
 # provisioner.
 persistentVolume:
   enabled: false
+  # NOTE: the number of existing claims must match the cluster size
+  existingClaims: []
   annotations: {}
   accessModes:
     - ReadWriteOnce