Kubernetes - pod FailedScheduling due to "No nodes are available that match all of the predicates: MatchInterPodAffinity (1)." - namespaces

Question

I am trying to create a deployment which create two pods whose node IP's match with two exisiting pods. For this I am defining PodAffinity as below
affinity:
podAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app
operator: In
values:
- {{ .Values.albId }}
topologyKey: "{{ .Values.topologyKey }}"
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app
operator: In
values:
- {{ .Values.name }}
topologyKey: "{{ .Values.topologyKey }}"
Since the namespace in which I want to create new pods is different from namespace in which I am referring exisitng pods, PodAffinity is failing.
Pods remain in pending state and when I do describe pod I get below error
Events:
FirstSeen LastSeen Count From SubObjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
28s 13s 6 default-scheduler Warning FailedScheduling No nodes are available that match all of the predicates: MatchInterPodAffinity (1).
From k8s docs- https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#inter-pod-affinity-and-anti-affinity-alpha-feature found that, I should define namespaces in PodAffinity and initialse it to empty list in order to allow cross namespace PodAffinity.
But I did not get any example from net on example of how to initialise namespaces to emplty list.
Please need help on this.

Answer 1

From the documentation you linked:
In addition to labelSelector and topologyKey, you can optionally specify a list namespaces of namespaces which the labelSelector should match against (this goes at the same level of the definition as labelSelector and topologyKey). If omitted, it defaults to the namespace of the pod where the affinity/anti-affinity definition appears. If defined but empty, it means “all namespaces”
Here is the example based on your yaml:
affinity:
podAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app
operator: In
values:
- {{ .Values.albId }}
topologyKey: "{{ .Values.topologyKey }}"
namespaces: [] # empty array
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: app
operator: In
values:
- {{ .Values.name }}
topologyKey: "{{ .Values.topologyKey }}"
namespaces: []