kubernetes集群配置dns服務
阿新 • • 發佈：2018-02-01
bin 留言 guarantee quest sch aaa .cn eve 介紹 本文將在前文的基礎上介紹在kubernetes集群環境中配置dns服務，在k8s集群中，pod的生命周期是短暫的，pod重啟後ip地址會產生變化，對於應用程序來說這是不可接受的，為解決這個問題，K8S集群巧妙的引入的dns服務來實現服務的發現，在k8s集群中dns總共需要使用4個組件，各組件分工如下：
etcd：DNS存儲
kube2sky：將Kubernetes Master中的service（服務）註冊到etcd。
skyDNS：提供DNS域名解析服務。
healthz：提供對skydns服務的健康檢查。
etcd：DNS存儲
kube2sky：將Kubernetes Master中的service（服務）註冊到etcd。
skyDNS：提供DNS域名解析服務。
healthz：提供對skydns服務的健康檢查。
一、下載相關鏡像文件，並納入本地倉庫統一管理
# docker pull docker.io/elcolio/etcd # docker pull docker.io/port/kubernetes-kube2sky # docker pull docker.io/skynetservices/skydns # docker pull docker.io/wu1boy/healthz # docker tag docker.io/elcolio/etcd registry.fjhb.cn/etcd # docker tag docker.io/port/kubernetes-kube2sky registry.fjhb.cn/kubernetes-kube2sky # docker tag docker.io/skynetservices/skydns registry.fjhb.cn/skydns # docker tag docker.io/wu1boy/healthz registry.fjhb.cn/healthz # docker push registry.fjhb.cn/etcd # docker push registry.fjhb.cn/kubernetes-kube2sky # docker push registry.fjhb.cn/skydns # docker push registry.fjhb.cn/healthz # docker images |grep fjhb
二、通過rc文件創建pod
這裏面一個pod包含了4個組件，一個組件運行在一個docker容器中
# cat skydns-rc.yaml apiVersion: v1 kind: ReplicationController metadata: name: kube-dns namespace: default labels: k8s-app: kube-dns version: v12 kubernetes.io/cluster-service: "true" spec: replicas: 1 selector: k8s-app: kube-dns version: v12 template: metadata: labels: k8s-app: kube-dns version: v12 kubernetes.io/cluster-service: "true" spec: containers: - name: etcd image: registry.fjhb.cn/etcd resources: limits: cpu: 100m memory: 50Mi requests: cpu: 100m memory: 50Mi command: - /bin/etcd - --data-dir - /tmp/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 volumeMounts: - name: etcd-storage mountPath: /tmp/data - name: kube2sky image: registry.fjhb.cn/kubernetes-kube2sky resources: limits: cpu: 100m memory: 50Mi requests: cpu: 100m memory: 50Mi args: - -kube_master_url=http://192.168.115.5:8080 - -domain=cluster.local - name: skydns image: registry.fjhb.cn/skydns resources: limits: cpu: 100m memory: 50Mi 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 - name: healthz image: registry.fjhb.cn/healthz resources: limits: cpu: 10m memory: 20Mi requests: cpu: 10m memory: 20Mi args: - -cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null - -port=8080 ports: - containerPort: 8080 protocol: TCP volumes: - name: etcd-storage emptyDir: {} dnsPolicy: Default
三、通過srv文件創建service
# cat skydns-svc.yaml apiVersion: v1 kind: Service metadata: name: kube-dns namespace: default labels: k8s-app: kube-dns kubernetes.io/cluster-service: "true" kubernetes.io/name: "KubeDNS" spec: selector: k8s-app: kube-dns clusterIP: 10.254.16.254 ports: - name: dns port: 53 protocol: UDP - name: dns-tcp port: 53 protocol: TCP
# kubectl create -f skydns-rc.yaml
# kubectl create -f skydns-svc.yaml
# kubectl get rc
# kubectl get pod
# kubectl get svc
# kubectl describe svc kube-dns
# kubectl describe rc kube-dns
# kubectl describe pod kube-dns-9fllp
Name: kube-dns-9fllp
Namespace: default
Node: 192.168.115.6/192.168.115.6
Start Time: Tue, 23 Jan 2018 10:55:19 -0500
Labels: k8s-app=kube-dns
kubernetes.io/cluster-service=true
version=v12
Status: Running
IP: 172.16.37.5
Controllers: ReplicationController/kube-dns
Containers:
etcd:
Container ID: docker://62ad76bfaca1797c5f43b0e9eebc04074169fce4cc15ef3ffc4cd19ffa9c8c19
Image: registry.fjhb.cn/etcd
Image ID: docker-pullable://docker.io/elcolio/etcd@sha256:3b4dcd35a7eefea9ce2970c81dcdf0d0801a778d117735ee1d883222de8bbd9f
Port:
Command:
/bin/etcd
--data-dir
/tmp/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
Limits:
cpu: 100m
memory: 50Mi
Requests:
cpu: 100m
memory: 50Mi
State: Running
Started: Tue, 23 Jan 2018 10:55:23 -0500
Ready: True
Restart Count: 0
Volume Mounts:
/tmp/data from etcd-storage (rw)
/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro)
Environment Variables: <none>
kube2sky:
Container ID: docker://6b0bc6e8dce83e3eee5c7e654fbaca693730623fb7936a1fd9d73de1a1dd8152
Image: registry.fjhb.cn/kubernetes-kube2sky
Image ID: docker-pullable://docker.io/port/kubernetes-kube2sky@sha256:0230d3fbb0aeb4ddcf903811441cf2911769dbe317a55187f58ca84c95107ff5
Port:
Args:
-kube_master_url=http://192.168.115.5:8080
-domain=cluster.local
Limits:
cpu: 100m
memory: 50Mi
Requests:
cpu: 100m
memory: 50Mi
State: Running
Started: Tue, 23 Jan 2018 10:55:25 -0500
Ready: True
Restart Count: 0
Volume Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro)
Environment Variables: <none>
skydns:
Container ID: docker://ebc2aaaa54e2f922e370e454ec537665d813c69d37a21e3afd908e6dad056627
Image: registry.fjhb.cn/skydns
Image ID: docker-pullable://docker.io/skynetservices/skydns@sha256:6f8a9cff0b946574bb59804016d3aacebc637581bace452db6a7515fa2df79ee
Ports: 53/UDP, 53/TCP
Args:
-machines=http://127.0.0.1:4001
-addr=0.0.0.0:53
-ns-rotate=false
-domain=cluster.local
Limits:
cpu: 100m
memory: 50Mi
Requests:
cpu: 100m
memory: 50Mi
State: Running
Started: Tue, 23 Jan 2018 10:55:27 -0500
Ready: True
Restart Count: 0
Volume Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro)
Environment Variables: <none>
healthz:
Container ID: docker://f1de1189fa6b51281d414d7a739b86494b04c8271dc6bb5f20c51fac15ec9601
Image: registry.fjhb.cn/healthz
Image ID: docker-pullable://docker.io/wu1boy/healthz@sha256:d6690c0a8cc4f810a5e691b6a9b8b035192cb967cb10e91c74824bb4c8eea796
Port: 8080/TCP
Args:
-cmd=nslookup kubernetes.default.svc.cluster.local 127.0.0.1 >/dev/null
-port=8080
Limits:
cpu: 10m
memory: 20Mi
Requests:
cpu: 10m
memory: 20Mi
State: Running
Started: Tue, 23 Jan 2018 10:55:29 -0500
Ready: True
Restart Count: 0
Volume Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-6pddn (ro)
Environment Variables: <none>
Conditions:
Type Status
Initialized True
Ready True
PodScheduled True
Volumes:
etcd-storage:
Type: EmptyDir (a temporary directory that shares a pod‘s lifetime)
Medium:
default-token-6pddn:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-6pddn
QoS Class: Guaranteed
Tolerations: <none>
Events:
FirstSeen LastSeen Count From SubObjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
7m 7m 1 {default-scheduler } Normal Scheduled Successfully assigned kube-dns-9fllp to 192.168.115.6
7m 7m 1 {kubelet 192.168.115.6} spec.containers{etcd} Normal Pulling pulling image "registry.fjhb.cn/etcd"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{etcd} Normal Pulled Successfully pulled image "registry.fjhb.cn/etcd"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{etcd} Normal Created Created container with docker id 62ad76bfaca1; Security:[seccomp=unconfined]
7m 7m 1 {kubelet 192.168.115.6} spec.containers{kube2sky} Normal Pulled Successfully pulled image "registry.fjhb.cn/kubernetes-kube2sky"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{etcd} Normal Started Started container with docker id 62ad76bfaca1
7m 7m 1 {kubelet 192.168.115.6} spec.containers{kube2sky} Normal Pulling pulling image "registry.fjhb.cn/kubernetes-kube2sky"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{kube2sky} Normal Created Created container with docker id 6b0bc6e8dce8; Security:[seccomp=unconfined]
7m 7m 1 {kubelet 192.168.115.6} spec.containers{skydns} Normal Pulled Successfully pulled image "registry.fjhb.cn/skydns"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{skydns} Normal Pulling pulling image "registry.fjhb.cn/skydns"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{kube2sky} Normal Started Started container with docker id 6b0bc6e8dce8
7m 7m 1 {kubelet 192.168.115.6} spec.containers{skydns} Normal Created Created container with docker id ebc2aaaa54e2; Security:[seccomp=unconfined]
7m 7m 1 {kubelet 192.168.115.6} spec.containers{skydns} Normal Started Started container with docker id ebc2aaaa54e2
7m 7m 1 {kubelet 192.168.115.6} spec.containers{healthz} Normal Pulling pulling image "registry.fjhb.cn/healthz"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{healthz} Normal Pulled Successfully pulled image "registry.fjhb.cn/healthz"
7m 7m 1 {kubelet 192.168.115.6} spec.containers{healthz} Normal Created Created container with docker id f1de1189fa6b; Security:[seccomp=unconfined]
7m 7m 1 {kubelet 192.168.115.6} spec.containers{healthz} Normal Started Started container with docker id f1de1189fa6b四、修改kubelet配置文件並重啟服務
註意:
--cluster-dns參數要和前面svc文件中的clusterIP參數一致
--cluster-domain參數要和前面rc文件中的-domain參數一致
集群內所有的kubelet節點都需要修改
# grep ‘KUBELET_ADDRESS‘ /etc/kubernetes/kubelet
KUBELET_ADDRESS="--address=192.168.115.5 --cluster-dns=10.254.16.254 --cluster-domain=cluster.local"
# systemctl restart kubelet五、運行一個busybox和curl進行測試
# cat busybox.yaml
apiVersion: v1
kind: Pod
metadata:
name: busybox
spec:
containers:
- name: busybox
image: docker.io/busybox
command:
- sleep
- "3600"# cat curl.yaml
apiVersion: v1
kind: Pod
metadata:
name: curl
spec:
containers:
- name: curl
image: docker.io/webwurst/curl-utils
command:
- sleep
- "3600"# kubectl create -f busybox.yaml
# kubectl create -f curl.yaml
通過busybox容器對kubernetes的service進行解析，發現service被自動解析成了對應的集群ip地址，而並不是172.16網段的docker地址
# kubectl get svc
# kubectl exec busybox -- nslookup frontend
# kubectl exec busybox -- nslookup redis-master
# kubectl exec busybox -- nslookup redis-slave
通過curl容器訪問前面創建的php留言板
# kubectl exec curl -- curl frontend
kubernetes集群配置dns服務