K
Q

How can I test the value of multiple keys at once in a node affinity rule? Is there a key wildcard?

2/25/2022

Let's assume I have a node labeled with the labels myKey1: 2, myKey2: 5, myKey3: 3, myKey4: 6. I now want to check if one of those labels has a value greater than 4 and if so schedule my workload on this node. For that I use the following nodeAffinity rule:

 spec:
   containers:
   - name: wl1
     image: myImage:latest
     imagePullPolicy: IfNotPresent
  affinity:
     nodeAffinity:
       requiredDuringSchedulingIgnoredDuringExecution:
         nodeSelectorTerms:
         - matchExpressions:
           - key: myKey1
             operator: Gt
             values:
             - 4
         nodeSelectorTerms:
         - matchExpressions:
           - key: myKey2
             operator: Gt
             values:
             - 4
         nodeSelectorTerms:
         - matchExpressions:
           - key: myKey3
             operator: Gt
             values:
             - 4
         nodeSelectorTerms:
         - matchExpressions:
           - key: myKey4
             operator: Gt
             values:
             - 4

I would instead love to use something shorter to be able to address a bunch of similar labels like e.g.

  affinity:
     nodeAffinity:
       requiredDuringSchedulingIgnoredDuringExecution:
         nodeSelectorTerms:
         - matchExpressions:
           - key: myKey*
             operator: Gt
             values:
             - 4

so basically using a key-wildcard and the different checks connected via a logical OR. Is this possible or is there another solution to check the value of multiple similar labels?

-- Wolfson
kubernetes
kubernetes-pod

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1 Answer

2/28/2022

As Matthias M wrote in the comment:

I would add an extra label to all nodes, which should match. I think that was the simplest solution. Was that also a solution for you? kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node

In your situation, it will actually be easier to just add another key and check only one condition. Alternatively, you can try to use set-based values:

Newer resources, such as Job, Deployment, ReplicaSet, and DaemonSet, support set-based requirements as well.

selector:
  matchLabels:
    component: redis
  matchExpressions:
    - {key: tier, operator: In, values: [cache]}
    - {key: environment, operator: NotIn, values: [dev]}

matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". matchExpressions is a list of pod selector requirements. Valid operators include In, NotIn, Exists, and DoesNotExist. The values set must be non-empty in the case of In and NotIn. All of the requirements, from both matchLabels and matchExpressions are ANDed together -- they must all be satisfied in order to match.

For more about it read also this question.

-- Mikołaj Głodziak
Source: StackOverflow