The semantics of label selectors, or the semantics of pod
affinity/anti-affinity, they both are very related.
What does "empty" mean in pod affinity/anti-affinity labelselectors, what
does null/{} mean in pod affinity/anti-affinity, are they the same?
I can use this to colocate a pod with another. what if the plan was to make
sure they were not colocated?
apiVersion: v1
kind: Pod
metadata:
name: nginx-pod3
spec:
affinity:
podAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchLabels:
app: nginx
topologyKey: kubernetes.io/hostname
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- topologyKey: kubernetes.io/hostname
containers:
- name: nginx
image: nginx:1.7.9
ports:
- containerPort: 80
On Friday, April 28, 2017 at 3:44:34 PM UTC-7, David Oppenheimer wrote:
>
> It's not clear to me if you are asking about YAML/API server behavior, or
> the semantics of label selectors, or the semantics of pod
> affinity/anti-affinity.
>
>
>
> On Fri, Apr 28, 2017 at 3:26 PM, 'Kenneth Massada' via Kubernetes user
> discussion and Q&A <kubernet...@googlegroups.com <javascript:>> wrote:
>
>> Could someone help clarify difference between empty and null?
>> https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/
>> says An empty label selector (that is, one with zero requirements) selects
>> every object in the collection. A null label selector (which is only
>> possible for optional selector fields) selects no objects consider this:
>> affinity: podAffinity: requiredDuringSchedulingIgnoredDuringExecution: -
>> labelSelector: matchLabels: app: nginx topologyKey:
>> kubernetes.io/hostname podAntiAffinity:
>> requiredDuringSchedulingIgnoredDuringExecution: - labelSelector:
>> matchLabels: null topologyKey: kubernetes.io/hostname The current
>> behavior is then schedule pod on all nodes that have a pod app:nginx BUT do
>> not schedule pod on "every" of the nodes. or schedule it none nodes and
>> node that has a pod app:nginx consider affinity: podAffinity:
>> requiredDuringSchedulingIgnoredDuringExecution: - labelSelector:
>> matchLabels: app: nginx topologyKey: kubernetes.io/hostname
>> podAntiAffinity: requiredDuringSchedulingIgnoredDuringExecution: -
>> topologyKey: kubernetes.io/hostname The current behavior is then
>> schedule pod on all nodes that have a pod app:nginx BUT do not schedule it
>> on "none" of the nodes. schedule it on all nodes and node that has a pod
>> app:nginx {}/null act as every Empty act as all so according to the YAML
>> construct "{}" is also null.
>> however, {} this looks more like empty? so is empty omitting?
>>
>> I guess the use case here is
>>
>> PodAffinity: app:nginx AND podAntiAffinity: NONE
>>
>> Kenneth
>>
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