This blog is a continuation of previous blog series https://goglides.io/2020/03/03/limit-range-kubernetes/
Limits/Requests Ratio
If LimitRangeItem.maxLimitRequestRatio is specified in the LimitRangeSpec,
- the named resource must have a request and limit
- both request and limit should be non-zero (>0)
- limit divided by request is less than or equal to the enumerated value
Following manifest (limitrange-limit-request-ratio.yaml) saying limit to be at most twice the amount of memory request,
apiVersion: v1
kind: Namespace
metadata:
name: limitrange-demo3
---
apiVersion: v1
kind: LimitRange
metadata:
name: limit-memory-ratio-pod
namespace: limitrange-demo3
spec:
limits:
- maxLimitRequestRatio:
memory: 2
type: Pod
apply YAML,
kubectl apply -f limitrange-limit-request-ratio.yaml
Output:
namespace/limitrange-demo3 created
limitrange/limit-memory-ratio-pod created
Describe the limitrange,
kubectl describe -f limitrange-limit-request-ratio.yaml
Output:
Name: limitrange-demo3
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Namespace","metadata":{"annotations":{},"name":"limitrange-demo3"}}
Status: Active
No resource quota.
Resource Limits
Type Resource Min Max Default Request Default Limit Max Limit/Request Ratio
---- -------- --- --- --------------- ------------- -----------------------
Pod memory - - - - 2
Name: limit-memory-ratio-pod
Namespace: limitrange-demo3
Type Resource Min Max Default Request Default Limit Max Limit/Request Ratio
---- -------- --- --- --------------- ------------- -----------------------
Pod memory - - - - 2
Now let’s test the constraint working or not,
First test failed conditions (invalid-limit-request.yaml)
apiVersion: v1
kind: Pod
metadata:
name: busybox3
namespace: limitrange-demo3
spec:
containers:
- name: busybox-cnt01
image: busybox
resources:
limits:
memory: "300Mi"
requests:
memory: "100Mi"
apply YAML
kubectl apply -f invalid-limit-request.yaml
Output:
Error from server (Forbidden): error when creating "limitrange-limit-request-ratio.yaml": pods "busybox3" is forbidden: memory max limit to request ratio per Pod is 2, but provided ratio is 3.000000
Here pod is failed to deploy because 300/100 > 2.
Now test with valid conditions (valid-limit-request.yaml)
apiVersion: v1
kind: Pod
metadata:
name: busybox4
namespace: limitrange-demo3
spec:
containers:
- name: busybox-cnt01
image: busybox
resources:
limits:
memory: "150Mi"
requests:
memory: "100Mi"
apply YAML
kubectl apply -f valid-limit-request.yaml
Output:
pod/busybox4 created
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About the Author: Balkrishna Pandey
