coredns 排錯記
摘要：
核心連結
https://kubernetes.io/docs/ta...
CoreDNS 安裝
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-syst...
核心連結
https://kubernetes.io/docs/ta...
CoreDNS 安裝
apiVersion: v1
kind: ServiceAccount
metadata:
name: coredns
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:coredns
rules:
- apiGroups:
- ""
resources:
- endpoints
- services
- pods
- namespaces
verbs:
- list
- watch
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
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: ConfigMap
metadata:
name: coredns
namespace: kube-system
data:
Corefile: |
.:53 {
log
errors
health
kubernetes cluster.local 172.0.0.0/8 in-addr.arpa ip6.arpa {
pods insecure
upstream
fallthrough in-addr.arpa ip6.arpa
}
prometheus :9153
proxy . /etc/resolv.conf
cache 30
reload
}
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: coredns
namespace: kube-system
labels:
k8s-app: coredns
kubernetes.io/name: "CoreDNS"
spec:
replicas: 2
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
selector:
matchLabels:
k8s-app: coredns
template:
metadata:
labels:
k8s-app: coredns
spec:
serviceAccountName: coredns
tolerations:
- key: "CriticalAddonsOnly"
operator: "Exists"
containers:
- name: coredns
image: hub.issll.com/kubernetes/coredns:1.1.0
imagePullPolicy: IfNotPresent
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
livenessProbe:
httpGet:
path: /health
port: 8081
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
dnsPolicy: Default
volumes:
- name: config-volume
configMap:
name: coredns
items:
- key: Corefile
path: Corefile
---
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: coredns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "CoreDNS"
spec:
selector:
k8s-app: coredns
clusterIP: 172.21.0.2
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
在master結點上執行
kubectl apply -f coredns.yaml
主要修改檔案
nodes結點上的/etc/resolv.conf
$ cat /etc/resolv.conf # Generated by NetworkManager search default.svc.cluster.local middleware.svc.cluster.local svc.cluster.local cluster.local nameserver 192.168.1.254
列印每個pods上的出錯日誌
for p in $(kubectl get pods --namespace=kube-system -l k8s-app=coredns -o name); do kubectl logs --namespace=kube-system $p; done
用busybox 檢驗coredns解析效果
kubectl exec -ti busybox -- nslookup redis-master
因為結點上的search 域的設定，等於
kubectl exec -ti busybox -- nslookup redis-master.middleware.svc.cluster.local
這裡 redis-master 是佈署在 middleware 名稱空間下的一個pod
CoreDNS 已知 Bug
重新載入時，在啟動新伺服器例項之前停止執行狀況處理程式。如果新伺服器無法啟動，則初始伺服器例項仍然可用且仍然提供DNS查詢，但Health處理程式保持關閉狀態。在成功重新載入或完全重新啟動CoreDNS之前，Health執行狀況不會回覆HTTP請求。
後記
在新 pod 建立後, CoreDNS 更新有問題, 需要解決