Added example for pod preferredDuringSchedulingIgnoredDuringExecution.

docs/concepts/configuration/assign-pod-node.md

@@ -173,14 +173,15 @@ Here's an example of a pod that uses pod affinity:
 
 {% include code.html language="yaml" file="pod-with-pod-affinity.yaml" ghlink="/docs/concepts/configuration/pod-with-pod-affinity.yaml" %}
 
-The affinity on this pod defines one pod affinity rule and one pod anti-affinity rule. Both
-must be satisfied for the pod to schedule onto a node. The
+The affinity on this pod defines one pod affinity rule and one pod anti-affinity rule. In this example, the
+`podAffinity` is `requiredDuringSchedulingIgnoredDuringExecution`
+while the `podAntiAffinity` is `preferredDuringSchedulingIgnoredDuringExecution`. The
 pod affinity rule says that the pod can schedule onto a node only if that node is in the same zone
 as at least one already-running pod that has a label with key "security" and value "S1". (More precisely, the pod is eligible to run
 on node N if node N has a label with key `failure-domain.beta.kubernetes.io/zone` and some value V
 such that there is at least one node in the cluster with key `failure-domain.beta.kubernetes.io/zone` and
 value V that is running a pod that has a label with key "security" and value "S1".) The pod anti-affinity
-rule says that the pod cannot schedule onto a node if that node is already running a pod with label
+rule says that the pod prefer to not schedule onto a node if that node is already running a pod with label
 having key "security" and value "S2". (If the `topologyKey` were `failure-domain.beta.kubernetes.io/zone` then
 it would mean that the pod cannot schedule onto a node if that node is in the same zone as a pod with
 label having key "security" and value "S2".) See the [design doc](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/podaffinity.md).

docs/concepts/configuration/pod-with-pod-affinity.yaml

@@ -14,14 +14,16 @@ spec:
             - S1
         topologyKey: failure-domain.beta.kubernetes.io/zone
     podAntiAffinity:
-      requiredDuringSchedulingIgnoredDuringExecution:
-      - labelSelector:
-          matchExpressions:
-          - key: security
-            operator: In
-            values:
-            - S2
-        topologyKey: kubernetes.io/hostname
+      preferredDuringSchedulingIgnoredDuringExecution:
+      - weight: 100
+        podAffinityTerm:
+          labelSelector:
+            matchExpressions:
+            - key: security
+              operator: In
+              values:
+              - S2
+          topologyKey: kubernetes.io/hostname
   containers:
   - name: with-pod-affinity
     image: gcr.io/google_containers/pause:2.0

docs/user-guide/node-selection/pod-with-pod-affinity.yaml

@@ -14,14 +14,16 @@ spec:
             - S1
         topologyKey: failure-domain.beta.kubernetes.io/zone
     podAntiAffinity:
-      requiredDuringSchedulingIgnoredDuringExecution:
-      - labelSelector:
-          matchExpressions:
-          - key: security
-            operator: In
-            values:
-            - S2
-        topologyKey: kubernetes.io/hostname
+      preferredDuringSchedulingIgnoredDuringExecution:
+      - weight: 100
+        podAffinityTerm:
+          labelSelector:
+            matchExpressions:
+            - key: security
+              operator: In
+              values:
+              - S2
+          topologyKey: kubernetes.io/hostname
   containers:
   - name: with-pod-affinity
     image: gcr.io/google_containers/pause:2.0