How to force Pods/Deployments to Master nodes?
A toleration does not mean that the pod must be scheduled on a node with such taints. It means that the pod tolerates such a taint. If you want your pod to be "attracted" to specific nodes you will need to attach a label to your dedicated=master tainted nodes and set nodeSelector in the pod to look for such label.
Attach the label to each of your special use nodes:
kubectl label nodes name_of_your_node dedicated=master
Kubernetes 1.6 and above syntax
Add the nodeSelector to your pod:
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: nginx-ingress-controller
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
spec:
replicas: 3
template:
metadata:
labels:
k8s-app: nginx-ingress-lb
name: nginx-ingress-lb
annotations:
spec:
nodeSelector:
dedicated: master
tolerations:
- key: dedicated
operator: Equal
value: master
effect: NoSchedule
[…]
If you don't fancy nodeSelector
you can add affinity:
under spec:
instead:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
matchExpressions:
- key: dedicated
operator: Equal
values: ["master"]
Pre 1.6 syntax
Add the nodeSelector to your pod:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-ingress-controller
namespace: kube-system
labels:
kubernetes.io/cluster-service: "true"
spec:
replicas: 3
template:
metadata:
labels:
k8s-app: nginx-ingress-lb
name: nginx-ingress-lb
annotations:
scheduler.alpha.kubernetes.io/tolerations: |
[
{
"key": "dedicated",
"operator": "Equal",
"value": "master",
"effect": "NoSchedule"
}
]
spec:
nodeSelector:
dedicated: master
[…]
If you don't fancy nodeSelector
you can also add an annotation like this:
scheduler.alpha.kubernetes.io/affinity: >
{
"nodeAffinity": {
"requiredDuringSchedulingIgnoredDuringExecution": {
"nodeSelectorTerms": [
{
"matchExpressions": [
{
"key": "dedicated",
"operator": "Equal",
"values": ["master"]
}
]
}
]
}
}
}
Keep in mind that NoSchedule will not evict pods that are already scheduled.
The information above is from https://kubernetes.io/docs/user-guide/node-selection/ and there are more details there.
tolerations:
- key: node-role.kubernetes.io/master
effect: NoSchedule
you might want to dive into the Assigning Pods to Nodes documentation. Basically you should add some labels to your nodes with sth like this:
kubectl label nodes <node-name> <label-key>=<label-value>
and then reference that within your Pod
specification like this:
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
containers:
- name: nginx
image: nginx
nodeSelector:
label: value
But I'm not sure if this works for non-critical addons when the specific node is tainted. More details could be found here