nodeSelector doesn't match the target node - kubernetes

Question

I want to deploy a simple nginx on my master node.
Basically, if i use the tolerations combined by nodeName everything is good:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: myapp
name: myapp-deployment
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
containers:
- image: nginx
name: myapp-container
tolerations:
- effect: NoExecute
operator: Exists
nodeName: master
The results:
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myapp-deployment-56d5887b9-fw5mj 1/1 Running 0 50s 100.32.0.4 master <none> <none>
But the problem is when i add a type=master label to my node and instead of nodeName, useing nodeselector, the deployment stays in Pending state!
Here are my steps:
Add label to my node: k label node master type=master
Check the node label:
$ k get no --show-labels
NAME STATUS ROLES AGE VERSION LABELS
master Ready control-plane 65d v1.24.1 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=master,kubernetes.io/os=linux,node-role.kubernetes.io/control-plane=,node.kubernetes.io/exclude-from-external-load-balancers=,type=master
Apply my new yaml file:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: myapp
name: myapp-deployment
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
containers:
- image: nginx
name: myapp-container
tolerations:
- effect: NoExecute
operator: Exists
nodeSelector:
type: master
Check the state:
$ k get po
NAME READY STATUS RESTARTS AGE
myapp-deployment-544784ff98-2qf7z 0/1 Pending 0 3s
Describe it:
Name: myapp-deployment-544784ff98-2qf7z
Namespace: default
Priority: 0
Node: <none>
Labels: app=myapp
pod-template-hash=544784ff98
Annotations: <none>
Status: Pending
IP:
IPs: <none>
Controlled By: ReplicaSet/myapp-deployment-544784ff98
Containers:
myapp-container:
Image: nginx
Port: <none>
Host Port: <none>
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-lbtsv (ro)
Conditions:
Type Status
PodScheduled False
Volumes:
kube-api-access-lbtsv:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: type=master
Tolerations: :NoExecute op=Exists
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedScheduling 111s default-scheduler 0/1 nodes are available: 1 node(s) had untolerated taint {node-role.kubernetes.io/master: }. preemption: 0/1 nodes are available: 1 Preemption is not helpful for scheduling.
Where am i wrong? What is my problem?
P.S: kubernetes version:
Client Version: v1.24.1
Kustomize Version: v4.5.4
Server Version: v1.24.1

Answer 1

Check your master node it might be having the taint set to NoSchedule
kubectl describe node <Node name> | grep Taint
If you want to run POD on master node use this config
tolerations:
- key: "node-role.kubernetes.io/master"
operator: "Exists"
effect: "NoSchedule"
nodeSelector:
node-role.kubernetes.io/master: ""
Read more about the Concept taint and toleration: https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/

Answer 2

Well, thanks to #Harsh, i finally finded the answer:
First i get the Taint on my master node:
$ kubectl describe node master | grep Taint
Taints: node-role.kubernetes.io/control-plane:NoSchedule
As you can see, the value of Taint here is NoSchedule, NOT NoExecute that i used before!
So, the configuration would be like this:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: myapp
name: myapp-deployment
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
containers:
- image: nginx
name: myapp-container
tolerations:
- effect: "NoSchedule" # just change this
operator: "Exists"
nodeSelector:
type: master
And now you can see everything is good!
NAME READY STATUS RESTARTS AGE
myapp-deployment-79676c54d4-grm94 1/1 Running 0 7s