k8s 集群搭建-08-DNS 插件-CoreDNS
八、DNS插件-CoreDNS
这部分我们部署kubernetes的DNS插件 - CoreDNS。
在早期的版本中dns组件以pod形式独立运行，为集群提供dns服务，所有的pod都会请求同一个dns服务。
从kubernetes 1.18版本开始 NodeLocal DnsCache 功能进入 stable 状态。
NodeLocal DNSCache通过daemon-set的形式运行在每个工作节点，作为节点上pod的dns缓存代理，从而避免了iptables的DNAT规则和connection tracking。极大提升了dns的性能。
1. 部署CoreDNS
在 node-1 节点执行：
# 设置 coredns 的 cluster-ip
# $ COREDNS_CLUSTER_IP=10.233.0.10（课程示例IP，需要将 10.xx.xx.xx网段 改为 192.xx.xx.xx ）
# 需要将示例IP修改为自己的IP：192.233.0.10
$ COREDNS_CLUSTER_IP=192.233.0.10
# 下载coredns配置all-in-one（addons/coredns.yaml）
# 替换cluster-ip
$ sed -i "s/\${COREDNS_CLUSTER_IP}/${COREDNS_CLUSTER_IP}/g" coredns.yaml
# 创建 coredns
$ kubectl apply -f coredns.yaml执行结果：
[root@hombd03 ~]# kubectl apply -f coredns.yaml
configmap/coredns created
serviceaccount/coredns created
clusterrole.rbac.authorization.k8s.io/system:coredns created
clusterrolebinding.rbac.authorization.k8s.io/system:coredns created
service/coredns created
deployment.apps/coredns createdcoredns.yaml 文件，需要替换 COREDNS_CLUSTER_IP；
---
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists
data:
Corefile: |
.:53 {
errors
health {
lameduck 5s
}
ready
kubernetes cluster.local in-addr.arpa ip6.arpa {
pods insecure
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
forward . /etc/resolv.conf {
prefer_udp
}
cache 30
loop
reload
loadbalance
}
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: Reconcile
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
labels:
kubernetes.io/bootstrapping: rbac-defaults
addonmanager.kubernetes.io/mode: Reconcile
name: system:coredns
rules:
- apiGroups:
- ""
resources:
- endpoints
- services
- pods
- namespaces
verbs:
- list
- watch
- apiGroups:
- ""
resources:
- nodes
verbs:
- get
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
addonmanager.kubernetes.io/mode: EnsureExists
name: system:coredns
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:coredns
subjects:
- kind: ServiceAccount
name: coredns
namespace: kube-system
---
apiVersion: v1
kind: Service
metadata:
name: coredns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/name: "coredns"
addonmanager.kubernetes.io/mode: Reconcile
annotations:
prometheus.io/port: "9153"
prometheus.io/scrape: "true"
spec:
selector:
k8s-app: kube-dns
clusterIP: ${COREDNS_CLUSTER_IP}
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
- name: metrics
port: 9153
protocol: TCP
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: "coredns"
namespace: kube-system
labels:
k8s-app: "kube-dns"
addonmanager.kubernetes.io/mode: Reconcile
kubernetes.io/name: "coredns"
spec:
replicas: 2
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 0
maxSurge: 10%
selector:
matchLabels:
k8s-app: kube-dns
template:
metadata:
labels:
k8s-app: kube-dns
annotations:
seccomp.security.alpha.kubernetes.io/pod: 'runtime/default'
spec:
priorityClassName: system-cluster-critical
nodeSelector:
kubernetes.io/os: linux
serviceAccountName: coredns
tolerations:
- key: node-role.kubernetes.io/master
effect: NoSchedule
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- topologyKey: "kubernetes.io/hostname"
labelSelector:
matchLabels:
k8s-app: kube-dns
nodeAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- weight: 100
preference:
matchExpressions:
- key: node-role.kubernetes.io/master
operator: In
values:
- ""
containers:
- name: coredns
image: "docker.io/coredns/coredns:1.6.7"
imagePullPolicy: IfNotPresent
resources:
# TODO: Set memory limits when we've profiled the container for large
# clusters, then set request = limit to keep this container in
# guaranteed class. Currently, this container falls into the
# "burstable" category so the kubelet doesn't backoff from restarting it.
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
args: [ "-conf", "/etc/coredns/Corefile" ]
volumeMounts:
- name: config-volume
mountPath: /etc/coredns
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9153
name: metrics
protocol: TCP
securityContext:
allowPrivilegeEscalation: false
capabilities:
add:
- NET_BIND_SERVICE
drop:
- all
readOnlyRootFilesystem: true
livenessProbe:
httpGet:
path: /health
port: 8080
scheme: HTTP
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 10
readinessProbe:
httpGet:
path: /ready
port: 8181
scheme: HTTP
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 10
dnsPolicy: Default
volumes:
- name: config-volume
configMap:
name: coredns
items:
- key: Corefile
path: Corefile2. 部署NodeLocal DNSCache
# 设置 coredns 的 cluster-ip
# $ COREDNS_CLUSTER_IP=10.233.0.10 （示例IP）
# 需要将示例IP修改为自己的IP：192.233.0.10
$ COREDNS_CLUSTER_IP=192.233.0.10
# 下载nodelocaldns配置all-in-one(addons/nodelocaldns.yaml)
# 替换cluster-ip
$ sed -i "s/\${COREDNS_CLUSTER_IP}/${COREDNS_CLUSTER_IP}/g" nodelocaldns.yaml
# 创建 nodelocaldns
$ kubectl apply -f nodelocaldns.yaml执行结果：
[root@homaybd03 ~]# kubectl apply -f nodelocaldns.yaml
configmap/nodelocaldns created
daemonset.apps/nodelocaldns created
serviceaccount/nodelocaldns created
[root@homaybd03 ~]# 查看是否在运行：
[root@homaybd03 ~]# kubectl get po -n kube-system
NAME READY STATUS RESTARTS AGE
calico-kube-controllers-6d9cdcd744-5v54f 1/1 Running 0 58m
calico-node-6zkzf 1/1 Running 0 58m
calico-node-mj59l 1/1 Running 0 58m
coredns-84646c885d-nlwhp 1/1 Running 0 10m
coredns-84646c885d-r9mz6 1/1 Running 0 10m
nginx-proxy-homaybd05 1/1 Running 0 7h34m
nodelocaldns-2nkcn 1/1 Running 0 2m36s
nodelocaldns-mpmz5 1/1 Running 0 2m36s可以看到coredns、nodelocaldns 已经在运行了
查看在哪些节点运行：
[root@homaybd03 ~]# kubectl get po -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
calico-kube-controllers-6d9cdcd744-5v54f 1/1 Running 0 62m 192.200.245.129 homaybd04 <none> <none>
calico-node-6zkzf 1/1 Running 0 62m 192.168.1.125 homaybd05 <none> <none>
calico-node-mj59l 1/1 Running 0 62m 192.168.1.124 homaybd04 <none> <none>
coredns-84646c885d-nlwhp 1/1 Running 0 14m 192.200.245.130 homaybd04 <none> <none>
coredns-84646c885d-r9mz6 1/1 Running 0 14m 192.200.72.194 homaybd05 <none> <none>
nginx-proxy-homaybd05 1/1 Running 0 7h37m 192.168.1.125 homaybd05 <none> <none>
nodelocaldns-2nkcn 1/1 Running 0 5m59s 192.168.1.124 homaybd04 <none> <none>
nodelocaldns-mpmz5 1/1 Running 0 5m59s 192.168.1.125 homaybd05 <none> <none>
[root@homaybd03 ~]#
nodelocaldns.yaml 文件，需要替换 COREDNS_CLUSTER_IP；
---
apiVersion: v1
kind: ConfigMap
metadata:
name: nodelocaldns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists
data:
Corefile: |
cluster.local:53 {
errors
cache {
success 9984 30
denial 9984 5
}
reload
loop
bind 169.254.25.10
forward . ${COREDNS_CLUSTER_IP} {
force_tcp
}
prometheus :9253
health 169.254.25.10:9254
}
in-addr.arpa:53 {
errors
cache 30
reload
loop
bind 169.254.25.10
forward . ${COREDNS_CLUSTER_IP} {
force_tcp
}
prometheus :9253
}
ip6.arpa:53 {
errors
cache 30
reload
loop
bind 169.254.25.10
forward . ${COREDNS_CLUSTER_IP} {
force_tcp
}
prometheus :9253
}
.:53 {
errors
cache 30
reload
loop
bind 169.254.25.10
forward . /etc/resolv.conf
prometheus :9253
}
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: nodelocaldns
namespace: kube-system
labels:
k8s-app: kube-dns
addonmanager.kubernetes.io/mode: Reconcile
spec:
selector:
matchLabels:
k8s-app: nodelocaldns
template:
metadata:
labels:
k8s-app: nodelocaldns
annotations:
prometheus.io/scrape: 'true'
prometheus.io/port: '9253'
spec:
priorityClassName: system-cluster-critical
serviceAccountName: nodelocaldns
hostNetwork: true
dnsPolicy: Default # Don't use cluster DNS.
tolerations:
- effect: NoSchedule
operator: "Exists"
- effect: NoExecute
operator: "Exists"
containers:
- name: node-cache
image: "registry.cn-hangzhou.aliyuncs.com/kubernetes-kubespray/dns_k8s-dns-node-cache:1.16.0"
resources:
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
args: [ "-localip", "169.254.25.10", "-conf", "/etc/coredns/Corefile", "-upstreamsvc", "coredns" ]
securityContext:
privileged: true
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
- containerPort: 9253
name: metrics
protocol: TCP
livenessProbe:
httpGet:
host: 169.254.25.10
path: /health
port: 9254
scheme: HTTP
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 10
readinessProbe:
httpGet:
host: 169.254.25.10
path: /health
port: 9254
scheme: HTTP
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 10
volumeMounts:
- name: config-volume
mountPath: /etc/coredns
- name: xtables-lock
mountPath: /run/xtables.lock
volumes:
- name: config-volume
configMap:
name: nodelocaldns
items:
- key: Corefile
path: Corefile
- name: xtables-lock
hostPath:
path: /run/xtables.lock
type: FileOrCreate
# Minimize downtime during a rolling upgrade or deletion; tell Kubernetes to do a "force
# deletion": https://kubernetes.io/docs/concepts/workloads/pods/pod/#termination-of-pods.
terminationGracePeriodSeconds: 0
updateStrategy:
rollingUpdate:
maxUnavailable: 20%
type: RollingUpdate
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: nodelocaldns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: Reconcile
官方文档地址
coredns官方文档：https://coredns.io/plugins/kubernetes/
NodeLocal DNSCache：https://kubernetes.io/docs/tasks/administer-cluster/nodelocaldns/
为者常成，行者常至
自由转载-非商用-非衍生-保持署名（创意共享3.0许可证）
