How to start kubernetes service on NodePort outside service-node-port-range default range? - azure

Question

I've been trying to start kubernetes-dashboard (and eventualy other services) on a NodePort outside the default port range with little success,
here is my setup:
Cloud provider: Azure (Not azure container service)
OS: CentOS 7
here is what I have tried:
Update the host
$ yum update
Install kubeadm
$ cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=http://yum.kubernetes.io/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF
$ setenforce 0
$ yum install -y docker kubelet kubeadm kubectl kubernetes-cni
$ systemctl enable docker && systemctl start docker
$ systemctl enable kubelet && systemctl start kubelet
Start the cluster with kubeadm
$ kubeadm init
Allow runing containers on master node, because we have a single node cluster
$ kubectl taint nodes --all dedicated-
Install a pod network
$ kubectl apply -f https://git.io/weave-kube
Our kubernetes-dashboard Deployment (# ~/kubernetes-dashboard.yaml
# Copyright 2015 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Configuration to deploy release version of the Dashboard UI.
#
# Example usage: kubectl create -f <this_file>
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
labels:
app: kubernetes-dashboard
name: kubernetes-dashboard
namespace: kube-system
spec:
replicas: 1
selector:
matchLabels:
app: kubernetes-dashboard
template:
metadata:
labels:
app: kubernetes-dashboard
# Comment the following annotation if Dashboard must not be deployed on master
annotations:
scheduler.alpha.kubernetes.io/tolerations: |
[
{
"key": "dedicated",
"operator": "Equal",
"value": "master",
"effect": "NoSchedule"
}
]
spec:
containers:
- name: kubernetes-dashboard
image: gcr.io/google_containers/kubernetes-dashboard-amd64:v1.5.1
imagePullPolicy: Always
ports:
- containerPort: 9090
protocol: TCP
args:
# Uncomment the following line to manually specify Kubernetes API server Host
# If not specified, Dashboard will attempt to auto discover the API server and connect
# to it. Uncomment only if the default does not work.
# - --apiserver-host=http://my-address:port
livenessProbe:
httpGet:
path: /
port: 9090
initialDelaySeconds: 30
timeoutSeconds: 30
---
kind: Service
apiVersion: v1
metadata:
labels:
app: kubernetes-dashboard
name: kubernetes-dashboard
namespace: kube-system
spec:
type: NodePort
ports:
- port: 8880
targetPort: 9090
nodePort: 8880
selector:
app: kubernetes-dashboard
Create our Deployment
$ kubectl create -f ~/kubernetes-dashboard.yaml
deployment "kubernetes-dashboard" created
The Service "kubernetes-dashboard" is invalid: spec.ports[0].nodePort: Invalid value: 8880: provided port is not in the valid range. The range of valid ports is 30000-32767
I found out that to change the range of valid ports I could set service-node-port-range option on kube-apiserver to allow a different port range,
so I tried this:
$ kubectl get po --namespace=kube-system
NAME READY STATUS RESTARTS AGE
dummy-2088944543-lr2zb 1/1 Running 0 31m
etcd-test2-highr 1/1 Running 0 31m
kube-apiserver-test2-highr 1/1 Running 0 31m
kube-controller-manager-test2-highr 1/1 Running 2 31m
kube-discovery-1769846148-wmbhb 1/1 Running 0 31m
kube-dns-2924299975-8vwjm 4/4 Running 0 31m
kube-proxy-0ls9c 1/1 Running 0 31m
kube-scheduler-test2-highr 1/1 Running 2 31m
kubernetes-dashboard-3203831700-qrvdn 1/1 Running 0 22s
weave-net-m9rxh 2/2 Running 0 31m
Add "--service-node-port-range=8880-8880" to kube-apiserver-test2-highr
$ kubectl edit po kube-apiserver-test2-highr --namespace=kube-system
{
"kind": "Pod",
"apiVersion": "v1",
"metadata": {
"name": "kube-apiserver",
"namespace": "kube-system",
"creationTimestamp": null,
"labels": {
"component": "kube-apiserver",
"tier": "control-plane"
}
},
"spec": {
"volumes": [
{
"name": "k8s",
"hostPath": {
"path": "/etc/kubernetes"
}
},
{
"name": "certs",
"hostPath": {
"path": "/etc/ssl/certs"
}
},
{
"name": "pki",
"hostPath": {
"path": "/etc/pki"
}
}
],
"containers": [
{
"name": "kube-apiserver",
"image": "gcr.io/google_containers/kube-apiserver-amd64:v1.5.3",
"command": [
"kube-apiserver",
"--insecure-bind-address=127.0.0.1",
"--admission-control=NamespaceLifecycle,LimitRanger,ServiceAccount,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota",
"--service-cluster-ip-range=10.96.0.0/12",
"--service-node-port-range=8880-8880",
"--service-account-key-file=/etc/kubernetes/pki/apiserver-key.pem",
"--client-ca-file=/etc/kubernetes/pki/ca.pem",
"--tls-cert-file=/etc/kubernetes/pki/apiserver.pem",
"--tls-private-key-file=/etc/kubernetes/pki/apiserver-key.pem",
"--token-auth-file=/etc/kubernetes/pki/tokens.csv",
"--secure-port=6443",
"--allow-privileged",
"--advertise-address=100.112.226.5",
"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
"--anonymous-auth=false",
"--etcd-servers=http://127.0.0.1:2379"
],
"resources": {
"requests": {
"cpu": "250m"
}
},
"volumeMounts": [
{
"name": "k8s",
"readOnly": true,
"mountPath": "/etc/kubernetes/"
},
{
"name": "certs",
"mountPath": "/etc/ssl/certs"
},
{
"name": "pki",
"mountPath": "/etc/pki"
}
],
"livenessProbe": {
"httpGet": {
"path": "/healthz",
"port": 8080,
"host": "127.0.0.1"
},
"initialDelaySeconds": 15,
"timeoutSeconds": 15,
"failureThreshold": 8
}
}
],
"hostNetwork": true
},
"status": {}
$ :wq
The following is the truncated response
# pods "kube-apiserver-test2-highr" was not valid:
# * spec: Forbidden: pod updates may not change fields other than `containers[*].image` or `spec.activeDeadlineSeconds`
So I tried a different approach, I edited the deployment file for kube-apiserver with the same change described above
and ran the following:
$ kubectl apply -f /etc/kubernetes/manifests/kube-apiserver.json --namespace=kube-system
And got this response:
The connection to the server localhost:8080 was refused - did you specify the right host or port?
So now i'm stuck, how can I change the range of valid ports?

Answer 1

You are specifying --service-node-port-range=8880-8880 wrong. You set it to one port only, Set it to a range.
Second problem: You are setting the service to use 9090 and it's not in the range.
ports:
- port: 80
targetPort: 9090
nodePort: 9090
API Server should have a deployment too, Try to editing the port-range in the deployment itself and delete the api server pod so it gets recreated via new config.

Answer 2

The Service node ports range is set to infrequently-used ports for a reason. Why do you want to publish this on every node? Do you really want that?
An alternative is to expose it on a semi-random nodeport, then use a proxy pod on a known node or set of nodes to access it via hostport.

Answer 3

This issue:
The connection to the server localhost:8080 was refused - did you specify the right host or port?
was caused by my port range excluding 8080, which kube-apiserver was serving on, so I could not send any updates to kubectl.
I fixed it by changing the port range to 8080-8881 and restarting the kubelet service like so:
$ service kubelet restart
Everything works as expected now.