Enforce Resources as Ratio

 1apiVersion : kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: enforce-resources-as-ratio
 5  annotations:
 6    policies.kyverno.io/title: Enforce Resources as Ratio
 7    policies.kyverno.io/category: Other
 8    policies.kyverno.io/severity: medium
 9    kyverno.io/kyverno-version: 1.6.0
10    policies.kyverno.io/minversion: 1.6.0
11    kyverno.io/kubernetes-version: "1.23"
12    policies.kyverno.io/subject: Pod
13    policies.kyverno.io/description: >-
14      Resource requests often need to be tailored to the type of workload in the container/Pod.
15      With many different types of applications in a cluster, enforcing hard limits on requests
16      or limits may not work and a ratio may be better suited instead. This policy checks every
17      container in a Pod and ensures that memory limits are no more than 2.5x its requests.      
18spec:
19  validationFailureAction: audit
20  rules:
21  - name: check-memory-requests-limits
22    match:
23      any:
24      - resources:
25          kinds:
26          - Pod
27    preconditions:
28      any:
29      - key: "{{ request.operation || 'BACKGROUND' }}"
30        operator: AnyIn
31        value:
32        - CREATE
33        - UPDATE
34    validate:
35      message: Limits may not exceed 2.5x the requests.
36      foreach:
37      - list: "request.object.spec.containers"
38        deny:
39          conditions:
40            any:
41              # Set resources.limits.memory equal to zero if not present and resources.requests.memory equal to 1m rather than zero
42              # to avoid undefined division error. No memory request in this case is basically the same as 1m. Kubernetes API server
43              # will automatically set requests=limits if only limits is defined.
44            - key: "{{ divide('{{ element.resources.limits.memory || '0' }}', '{{ element.resources.requests.memory || '1m' }}') }}"
45              operator: GreaterThan
46              value: 2.5