Kubernetes集群部署DNS服務
在kubernetes中每一個service都會被分配一個虛擬IP,每一個Service在正常情況下都會長時間不會改變,這個相對於pod的不定IP,對於集群中APP的使用相對是穩定的。
但是Service的信息註入到pod目前使用的是環境變量的方式,並且十分依賴於pod(rc)和service的創建順序,這使得這個集群看起來又不那麽完美,於是kubernetes以插件的方式引入了DNS系統,利用DNS對Service進行一個映射,這樣我們在APP中直接使用域名進行引用,避免了之前的變量泛濫問題,也避免了創建順序的尷尬局面。
組件:
?SkyDNS 提供DNS解析服務
?Kube2sky 監聽kubernetes,當有Service創建時,生成相應的記錄到SkyDNS
1.下載創建dns的鏡像(node節點下載)
docker pull docker.gaoxiaobang.com/kubernetes/etcd-amd64:2.2.1
docker pull docker.gaoxiaobang.com/kubernetes/kube2sky:1.14
docker pull docker.gaoxiaobang.com/kubernetes/skydns:2015-10-13-8c72f8c
docker pull docker.gaoxiaobang.com/kubernetes/exechealthz:1.0
根據namespace分為不同的名稱空間,將系統服務統一放到一個單獨的空間:kube-system,由於默認空間只有default,我們首先要創建kube-system空間。
vim kube-system.yaml,內容如下:
apiVersion: v1
kind: Namespace
metadata:
name: kube-system
3.在master服務器上編輯ReplicationController文件
vim skydns-rc.yaml,內容如下,記得修改紅色字體部分:
apiVersion: v1
kind: ReplicationController
metadata:
namespace: kube-system
labels:
k8s-app: kube-dns
version: v11
kubernetes.io/cluster-service: "true"
spec:
replicas: 1
selector:
k8s-app: kube-dns
version: v11
template:
metadata:
labels:
k8s-app: kube-dns
version: v11
kubernetes.io/cluster-service: "true"
spec:
containers:
- name: etcd
image: docker.gaoxiaobang.com/kubernetes/etcd-amd64:2.2.1
resources:
limits:
cpu: 100m
memory: 500Mi
requests:
cpu: 100m
memory: 50Mi
command:- /usr/local/bin/etcd
- -data-dir
- /var/etcd/data
- -listen-client-urls
- http://127.0.0.1:2379,http://127.0.0.1:4001
- -advertise-client-urls
- http://127.0.0.1:2379,http://127.0.0.1:4001
- -initial-cluster-token
- skydns-etcd
- name: kube2sky
image: docker.gaoxiaobang.com/kubernetes/kube2sky:1.14
args:- --domain=cluster.local
- --kube-master-url=http://192.168.1.10:8080
resources:
limits:
cpu: 100m
memory: 200Mi
requests:
cpu: 100m
memory: 50Mi
- name: skydns
image: docker.gaoxiaobang.com/kubernetes/skydns:2015-10-13-8c72f8c
resources:
limits:
cpu: 100m
memory: 200Mi
requests:
cpu: 100m
memory: 50Mi
args:- -machines=http://127.0.0.1:4001
- -addr=0.0.0.0:53
- -ns-rotate=false
- -domain=cluster.local.
ports: - containerPort: 53
name: dns
protocol: UDP - containerPort: 53
name: dns-tcp
protocol: TCP
livenessProbe:
httpGet:
path: /healthz
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
readinessProbe:
httpGet:
path: /readiness
port: 8080
scheme: HTTP
initialDelaySeconds: 30
timeoutSeconds: 5
- name: healthz
image: docker.gaoxiaobang.com/kubernetes/exechealthz:1.0
resources:
limits:
cpu: 10m
memory: 20Mi
requests:
cpu: 10m
memory: 20Mi
args:- -cmd=nslookup kubernetes.default.svc.cluster.local localhost >/dev/null
- -port=8080
ports: - containerPort: 8080
protocol: TCP
volumes:
- name: etcd-storage
emptyDir: {}
dnsPolicy: Default
4.在master上創建skydns服務文件skydns-service.yaml
在創建skydns-service.yaml之前,需要手動為dns指定一個cluster-ip
你需要查看你的/etc/kubernetes/apiserver文件和kubernetes的cluster-ip:
[root@k8s-master dns]# cat /etc/kubernetes/apiserver | grep KUBE_SERVICE_ADDRESSES
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=172.25.0.0/24"
[root@k8s-master dns]# kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 172.25.0.1 <none> 443/TCP 19d
如果這兩個ip地址屬於同一網段,則從172.25.0.0中挑選一個IP充當dns的cluster-ip;
如果不一樣,以kubernetes的cluster-ip為準,修改apiserver的網絡地址範圍,重啟apiserver,然後從172.25.0.0中挑選一個IP作為dns的cluster-ip
創建skydns-service.yaml文件,註意修改紅色部分,這裏我選的dns-clusterip是172.25.0.254
vim skydns-service.yaml,內容如下:
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "KubeDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 172.25.0.254
ports:
- name: dns
port: 53
protocol: UDP - name: dns-tcp
port: 53
protocol: TCP
5.在集群中創建cluster-dns解析應用
?創建Namespace
kubectl create -f kube-system.yaml
?創建ReplicationController
kubectl create -f skydns-rc.yaml
?創建Service
kubectl create -f skydns-service.yaml
刪除就是將上面三個命令中的“create”換成“delete”
6.查看dns-pod的啟動狀態
[root@ k8s-master dns]# kubectl get pod --namespace=kube-system
NAME READY STATUS RESTARTS AGE
kube-dns-v11-ey14j 4/4 Running 8 1d
7.查看skydns-service.yaml文件中定義的Service的信息。
[root@ k8s-master dns]# kubectl get svc --namespace=kube-system
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns 172.25.0.254 <none> 53/UDP,53/TCP 1d
8.測試DNS功能
(1) 獲取busybox鏡像
docker pull busybox:latest
(2) 編輯busybox的pod的yaml文件
vim busybox.yaml,內容如下:
apiVersion: v1
kind: Pod
metadata:
name: busybox
namespace: default
spec:
containers:
- image: busybox:latest
command:- sleep
- "3600"
imagePullPolicy: IfNotPresent
name: busybox
restartPolicy: Always
(3) 創建busybox的pod:
kubectl create -f busybox.yaml
pod啟動狀態:
[root@k8s-master dns]# kubectl get pods
NAME READY STATUS RESTARTS AGE
busybox 1/1 Running 2 2h
(4) 使用busybox自帶的nslookup測試dns
kubernetets集群搭建完畢之後都會有一個默認的cluster-ip,可通過命令查看:
[root@k8s-master dns]# kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 172.25.0.1 <none> 443/TCP 19d
開始測試,解析時間可能有點小長,耐心等待:
[root@k8s-master dns]# kubectl exec busybox nslookup kubernetes.default
Server: 172.25.0.254
Address 1: 172.25.0.254
Name: kubernetes.default
Address 1: 172.25.0.1
解析成功,註意,上面的kubernetes.default參數,kubernetes為service的name,default為k8s的默認命名空間,如果你查詢的不是default名稱空間裏的域名,則更改default,例如下面這個例子:
[root@k8s-master dns]# kubectl get service -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 172.25.0.254 <none> 53/UDP,53/TCP 2h
如果你想解析“kube-dns”這個域名對應的IP,需要這樣寫:
[root@k8s-master dns]# kubectl exec busybox nslookup kube-dns.kube-system
Server: 172.25.0.254
Address 1: 172.25.0.254
Name: kube-dns.kube-system
Address 1: 172.25.0.254
至此,kubernetes的DNS搭建成功
Kubernetes集群部署DNS服務