CoreDNS 其實(shí)就是一個(gè) DNS 服務(wù),而 DNS 作為一種常見(jiàn)的服務(wù)發(fā)現(xiàn)手段,所以很多開(kāi)源項(xiàng)目以及工程師都會(huì)使用 CoreDNS 為集群提供服務(wù)發(fā)現(xiàn)的功能,Kubernetes 就在集群中使用 CoreDNS 解決服務(wù)發(fā)現(xiàn)的問(wèn)題。
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如果想要在分布式系統(tǒng)實(shí)現(xiàn)服務(wù)發(fā)現(xiàn)的功能,CoreDNS 其實(shí)是一個(gè)非常好的選擇,CoreDNS作為一個(gè)已經(jīng)進(jìn)入CNCF并且在Kubernetes中作為DNS服務(wù)使用的應(yīng)用,其本身的穩(wěn)定性和可用性已經(jīng)得到了證明,同時(shí)它基于插件實(shí)現(xiàn)的方式非常輕量并且易于使用,插件鏈的使用也使得第三方插件的定義變得非常的方便。
整個(gè) CoreDNS 服務(wù)都建立在一個(gè)使用 Go 編寫的 HTTP/2 Web 服務(wù)器 Caddy 。
v1.13
172.20.101.157
172.20.101.165
172.20.101.164
10.254.0.0/16
10.254.0.10
下載地址1:
wget https://github.com/coredns/deployment/archive/master.zip
unzip master.zip
下載地址2:
git clone https://github.com/coredns/deployment.git
kubectl get pods -o wide -n=kube-system
#刪除命令
kubectl delete --namespace=kube-system deployment ****-dns
cd /workspace/
git clone https://github.com/coredns/deployment.git
cd /workspace/deployment/kubernetes
[root@node01 kubernetes]# ll
CoreDNS-k8s_version.md
coredns.yaml.sed
deploy.sh
README.md
rollback.sh
Scaling_CoreDNS.md
Upgrading_CoreDNS.md
deploy.sh 是一個(gè)用于在已經(jīng)運(yùn)行kube-dns的集群中生成運(yùn)行CoreDNS部署文件(manifest)的工具腳本。它使用 coredns.yaml.sed文件作為模板,創(chuàng)建一個(gè)ConfigMap和CoreDNS的deployment,然后更新集群中已有的kube-dns 服務(wù)的selector使用CoreDNS的deployment。重用已有的服務(wù)并不會(huì)在服務(wù)的請(qǐng)求中發(fā)生沖突。
usage: ./deploy.sh [ -r REVERSE-CIDR ] [ -i DNS-IP ] [ -d CLUSTER-DOMAIN ] [ -t YAML-TEMPLATE ]
-r : Define a reverse zone for the given CIDR. You may specifcy this option more
than once to add multiple reverse zones. If no reverse CIDRs are defined,
then the default is to handle all reverse zones (i.e. in-addr.arpa and ip6.arpa)
-i : Specify the cluster DNS IP address. If not specificed, the IP address of
the existing "kube-dns" service is used, if present.
-s : Skips the translation of kube-dns configmap to the corresponding CoreDNS Corefile configuration.
參考地址:
https://github.com/coredns/deployment/blob/master/kubernetes/CoreDNS-k8s_version.md
Kubernetes v1.14 ==> CoreDNS v1.3.1
Kubernetes v1.13 ==> CoreDNS v1.2.6 <<===本環(huán)境使用版本
./deploy.sh -r 10.254.0.0/16 -i 10.254.0.10 -d cluster.local -t coredns.yaml.sed -s >coredns.yaml
[root@node01 kubernetes]# more coredns.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
---
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns
namespace: kube-system
data:
Corefile: |
.:53 {
errors
health
kubernetes cluster.local 10.254.0.0/16 { 《+====監(jiān)聽(tīng)域名和CIDR
pods insecure
upstream
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
forward . /etc/resolv.conf
cache 30
loop
reload
loadbalance
}
---
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
containers:
- name: coredns
image: coredns/coredns:1.3.1 《===修改鏡像版本:image: coredns/coredns:1.2.6
imagePullPolicy: IfNotPresent
resources:
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
args: [ "-conf", "/etc/coredns/Corefile" ]
volumeMounts:
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
kubectl apply -f coredns.yaml
serviceaccount/coredns unchanged
clusterrole.rbac.authorization.k8s.io/system:coredns unchanged
clusterrolebinding.rbac.authorization.k8s.io/system:coredns unchanged
configmap/coredns configured
deployment.apps/coredns configured
service/kube-dns created
首先要確定使用鏡像是對(duì)的,執(zhí)行方法如下:
./deploy.sh -r 10.254.0.0/16 -i 10.254.0.10 -t coredns.yaml -d | kubectl apply -f -
kubectl get svc -o wide -n=kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kube-dns ClusterIP 10.254.0.10 53/UDP,53/TCP,9153/TCP 84s k8s-app=kube-dns
kubectl get pods -o wide -n=kube-system
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-b97f7df6d-gwjzj 1/1 Running 0 15h 10.254.100.3 172.20.101.166
coredns-b97f7df6d-jq7q6 1/1 Running 0 15h 10.254.87.3 172.20.101.160
[root@node04 ~]# docker logs 2076a98b7461
.:53
2019-03-14T10:58:53.9Z [INFO] CoreDNS-1.2.6
2019-03-14T10:58:53.9Z [INFO] linux/amd64, go1.11.2, 756749c
CoreDNS-1.2.6
linux/amd64, go1.11.2, 756749c
[INFO] plugin/reload: Running configuration MD5 = 2f886b3d3ac0d768123559b4705a7dbb
修改master節(jié)點(diǎn)和所有node節(jié)點(diǎn)的/etc/systemd/system/kube-kubelet.service,
修改內(nèi)容如紅色所注,與Corefile中的值對(duì)應(yīng)。
10.254.0.0/16
10.254.0.10
vi /k8s/kubnode/cfg/kubelet
KUBELET_OPTS="--logtostderr=true \
--v=4 \
--hostname-override=172.20.101.166 \
--kubeconfig=/k8s/kubnode/cfg/kubelet.kubeconfig \
--bootstrap-kubeconfig=/k8s/kubnode/cfg/bootstrap.kubeconfig \
--config=/k8s/kubnode/cfg/kubelet.config \
--cert-dir=/k8s/kubnode/ssl \
--pod-infra-container-image=registry.cn-hangzhou.aliyuncs.com/google-containers/pause-amd64:3.0"
#添加內(nèi)容如下
--cluster-dns=10.254.0.10 \
--cluster-domain=cluster.local.
#或者添加配置到 /etc/systemd/system/kube-kubelet.service
### 重啟 kubelet 服務(wù)
systemctl daemon-reload
systemctl enable kubelet
systemctl restart kubelet
systemctl status kubelet -l
kubectl run nginx --replicas=2 --image=nginx:alpine --port=80
kubectl expose deployment nginx --type=NodePort --name=example-service-nodeport
kubectl expose deployment nginx --name=example-service
kubectl run curl --image=radial/busyboxplus:curl
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
curl-66959f6557-879c6 1/1 Running 0 4m52s 10.254.87.4 172.20.101.160
nginx-665764c8c9-dgjgv 1/1 Running 0 7m19s 10.254.100.2 172.20.101.166
nginx-665764c8c9-z9rrm 1/1 Running 0 7m19s 10.254.87.2 172.20.101.160
[root@node01 kubernetes]#
kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
example-service ClusterIP 10.254.210.43 80/TCP 9s run=nginx
example-service-nodeport NodePort 10.254.204.43 80:36136/TCP 14s run=nginx
kubernetes ClusterIP 10.254.0.1 443/TCP 105m
[root@node04 ~]# docker exec -it f18900873efe sh
ping qq.com
PING qq.com (111.161.64.48): 56 data bytes
64 bytes from 111.161.64.48: seq=0 ttl=47 time=6.331 ms
64 bytes from 111.161.64.48: seq=1 ttl=47 time=6.293 ms
[ root@curl-66959f6557-879c6:/ ]$ nslookup kubernetes
Server: 10.254.0.10
Address 1: 10.254.0.10 kube-dns.kube-system.svc.cluster.local
Name: kubernetes
Address 1: 10.254.0.1 kubernetes.default.svc.cluster.local
[ root@curl-66959f6557-879c6:/ ]$
curl example-service
Welcome to nginx!
Welcome to nginx!
...........................
Thank you for using nginx.
kubectl get svc
kubectl delete svc example-service example-service-nodeport
kubectl get deployment
kubectl delete deploy nginx curl
kubectl delete svc kube-dns -n=kube-system
[root@node01 kubernetes]#
curl example-service
curl: (6) Could not resolve host: example-service; Unknown error
[root@node01 kubernetes]# curl example-service
修改 kubelet 啟動(dòng)配置文件 (node節(jié)點(diǎn))
vi /k8s/kubnode/cfg/kubelet
KUBELET_OPTS="--logtostderr=true \
--v=4 \
--hostname-override=172.20.101.166 \
--kubeconfig=/k8s/kubnode/cfg/kubelet.kubeconfig \
--bootstrap-kubeconfig=/k8s/kubnode/cfg/bootstrap.kubeconfig \
--config=/k8s/kubnode/cfg/kubelet.config \
--cert-dir=/k8s/kubnode/ssl \
--pod-infra-container-image=registry.cn-hangzhou.aliyuncs.com/google-containers/pause-amd64:3.0"
#添加內(nèi)容如下
--cluster-dns=10.3.0.10 \
--cluster-domain=cluster.local.
#或者添加配置到 /etc/systemd/system/kube-kubelet.service
systemctl daemon-reload
systemctl enable kubelet
systemctl restart kubelet
systemctl status kubelet -l
[root@node01 coredns]# ./deploy.sh 10.254.0.0/16 cluster.local | kubectl apply -f -
Error from server (NotFound): services "kube-dns" not found
error: no objects passed to apply
報(bào)錯(cuò):
./deploy.sh: line 39: jq: command not found
解決辦法:
因?yàn)轫?xiàng)目使用了jq命令,需要安裝jq程序
yum -y install jq conntrack-tools
https://juejin.im/post/5b45cea9f265da0f652370ce#heading-33
https://www.cnblogs.com/boshen-hzb/p/7511432.html
http://lizhe.name/node/326
https://github.com/minminmsn/k8s1.13/blob/master/kubernetes/kubernetes1.13.1%2Betcd3.3.10%2Bflanneld0.10%E9%9B%86%E7%BE%A4%E9%83%A8%E7%BD%B2.md