Add configurable affinity to CouchDB StatefulSet (#7224)

Signed-off-by: Sergey Nazarov <natarajaya@gmail.com>

incubator/couchdb/Chart.yaml

@@ -1,5 +1,5 @@
 name: couchdb
-version: 0.2.0
+version: 0.2.1
 appVersion: 2.2.0
 description: A database featuring seamless multi-master sync, that scales from
   big data to mobile, with an intuitive HTTP/JSON API and designed for

incubator/couchdb/README.md

@@ -103,6 +103,7 @@ A variety of other parameters are also configurable. See the comments in the
 | `persistentVolume.accessModes`  | ReadWriteOnce                          |
 | `persistentVolume.storageClass` | Default for the Kube cluster           |
 | `podManagementPolicy`           | Parallel                               |
+| `affinity`                      |                                        |
 | `resources`                     |                                        |
 | `service.enabled`               | true                                   |
 | `service.type`                  | ClusterIP                              |

incubator/couchdb/templates/statefulset.yaml

@@ -94,6 +94,10 @@ spec:
 {{- if .Values.nodeSelector }}
       nodeSelector:
 {{ toYaml .Values.nodeSelector | indent 8 }}
+{{- end }}
+{{- with .Values.affinity }}
+      affinity:
+{{ toYaml . | indent 8 }}
 {{- end }}
       volumes:
         - name: config-storage

incubator/couchdb/values.yaml

@@ -54,6 +54,19 @@ helperImage:
 ## `OrderedReady`
 podManagementPolicy: Parallel
 
+## To better tolerate Node failures, we can prevent Kubernetes scheduler from
+## assigning more than one Pod of CouchDB StatefulSet per Node using podAntiAffinity.
+affinity:
+  # podAntiAffinity:
+  #   requiredDuringSchedulingIgnoredDuringExecution:
+  #     - labelSelector:
+  #         matchExpressions:
+  #           - key: "app"
+  #             operator: In
+  #             values:
+  #             - couchdb
+  #       topologyKey: "kubernetes.io/hostname"
+
 ## A StatefulSet requires a headless Service to establish the stable network
 ## identities of the Pods, and that Service is created automatically by this
 ## chart without any additional configuration. The Service block below refers