Node Affinity
node affinity ——————→ restrict pod to be deployed on specific node.
Please note
please node ———→ Node selector and Node affinity restrict pod to be deployed on nodes that have certain labels
How to use node affinity ?
1) label node
$ kubectl label nodes node_name key=value
2) use affinity section on pod definition
spec:
containers:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
-key: “key“
operator: “Equal“
values
key: size
operator: Exists ————→ check if there is label on node called size
NodeAffinity Types ————————>
1) Available
a) requiredDuringSchedulingIgnoredDuringExecution ————> means labels on nodes must be existing when deploying pod && after deployinh pod if labels is deleted or edited no worries already deployed pods will not affected.
b) preferedDuringSchedulingIgnoredDuringExecution —————→ means labels on nodes prefered to be existing when deploying pod if there is no labels no issue && after deployinh pod if labels is deleted or edited no worries deployed pods will not affected.
2) Planned
requiredDuringSchedulingRequiredDuringExecution—————→ means labels on nodes must be exist before deploying pod and after deploying pod if labels are deleted or edited pod will be evicted from nodes.
DuringScheduling —————> When create pod for first time
DuringExecution ———————> After deploying pod
Apply a label color=blue to node node01
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Create a new deployment named blue with the nginx image and 3 replicas.
apiVersion: apps/v1
kind: Deployment
metadata:
name: blue
spec:
replicas: 3
selector:
matchLabels:
app: DEV
template:
metadata:
labels:
app: DEV
spec:
containers:
- name: c1
image: nginx
Set Node Affinity to the deployment to place the pods on node01 only.
Name: blue
Replicas: 3
Image: nginx
NodeAffinity: requiredDuringSchedulingIgnoredDuringExecution
Key: color
value: blue
Create a new deployment named red with the nginx image and 2 replicas, and ensure it gets placed on the controlplane node only.
Use the label key - node-role.kubernetes.io/control-plane - which is already set on the controlplane node.
apiVersion: apps/v1
kind: Deployment
metadata:
name: red
spec:
replicas: 2
selector:
matchLabels:
app: Test
template:
metadata:
labels:
app: Test
spec:
containers:
- name: c1
image: nginx
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: node-role.kubernetes.io/control-plane
operator: Exists