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CoreDNS — DNS-сервер для мира cloud native и Service Discovery для Kubernetes



Open Source- CoreDNS — 008. «DNS-, (middleware), - DNS». , CoreDNS CNCF (Cloud Native Computing Foundation), Kubernetes, Prometheus, CNI, containerd, rkt , , « » (cloud native).

CoreDNS, ?

CoreDNS


CoreDNS — DNS-, 2016 ( Apache License v2) - Caddy, Go. HTTP- Caddy httpserver, Handler ( HTTP-) Middleware ( , Handler , — ). CoreDNS, : «CoreDNS — DNS-, middleware».

CoreDNS SkyDNS — service discovery, NoSQL- etcd DNS- ( SRV-) . SkyDNS etcd, , DNS-, «» . , SkyDNS 7 ( etcd 3) , CoreDNS .

CoreDNS etcd , DNS-. Kubernetes (, , , etcd… ), CoreDNS kube-dns. ( , , .)

: DNS-: SkyDNS, CoreDNS, kube-dns — , . , , -, kube-dns SkyDNS DNS-, Kubernetes. -, CoreDNS SkyDNS — Miek Gieben — SRE Google, Go DNS-. CoreDNS «» kube-dns, .

CoreDNS


UDP/TCP, TLS (RFC 7858) gRPC. :


CoreDNS:


( ) , ( Caddy/CoreDNS) — middleware. , middleware.


CoreDNS, middleware

John Belamaric, Infoblox CoreDNS, :
DNS-, , DNS. CoreDNS , . , cloud-native.

CoreDNS CNCF?


:
— CoreDNS DNS- service discovery cloud-native. CNCF cloud-native. , [ ]. — CNCF, CoreDNS .

CNCF Chris Aniszczyk (COO CNCF), , «CoreDNS cloud-native CNCF», «CoreDNS — Kubernetes».

: CoreDNS (inception) CNCF, : , , incubating graduated.

.

CoreDNS Service Discovery Kubernetes


, CoreDNS kube-dns — Kubernetes, . — , Service Discovery DNS Kubernetes. , « Kube-DNS CoreDNS». 1.0.0 kube-dns — CoreDNS 005 (, , , kube-dns).

CoreDNS Service Discovery Kubernetes, (ConfigMap Deployment) Bash- deploy.sh . , ( ):

$ ./deploy.sh 10.3.0.0/24 cluster.local


:

apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        log stdout
        health
        kubernetes cluster.local {
          cidrs 10.3.0.0/24
        }
        proxy . /etc/resolv.conf
        cache 30
    }
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: coredns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "CoreDNS"
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: coredns
  template:
    metadata:
      labels:
        k8s-app: coredns
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
        scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
    spec:
      containers:
      - name: coredns
        image: coredns/coredns:latest
        imagePullPolicy: Always
        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: 8080
            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: 10.3.0.10
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP

( Corefile) cidrs 10.3.0.0/24 Kubernetes middleware CoreDNS, PTR- 0.3.10.in-addr.arpa.

Kubernetes:

$ ./deploy.sh 10.3.0.0/24 | kubectl apply -f -
configmap "coredns" created
deployment "coredns" created
service "kube-dns" configured

… , DNS- :

$ kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
Waiting for pod default/dnstools to be running, status is Pending, pod ready: false
If you don't see a command prompt, try pressing enter.
# host kubernetes
kubernetes.default.svc.cluster.local has address 10.3.0.1
# host kube-dns.kube-system
kube-dns.kube-system.svc.cluster.local has address 10.3.0.10
# host 10.3.0.1
1.0.3.10.in-addr.arpa domain name pointer kubernetes.default.svc.cluster.local.
# host 10.3.0.10
10.0.3.10.in-addr.arpa domain name pointer kube-dns.kube-system.svc.cluster.local.

CoreDNS? CoreDNS, DNS-:
#     CoreDNS
$ kubectl get --namespace kube-system pods
NAME                                    READY     STATUS    RESTARTS   AGE
coredns-3558181428-0zhnh                1/1       Running   0          2m
coredns-3558181428-xri9i                1/1       Running   0          2m
heapster-v1.2.0-4088228293-a8gkc        2/2       Running   0          126d
kube-apiserver-10.222.243.77            1/1       Running   2          126d
kube-controller-manager-10.222.243.77   1/1       Running   2          126d
kube-proxy-10.222.243.77                1/1       Running   2          126d
kube-proxy-10.222.243.78                1/1       Running   0          126d
kube-scheduler-10.222.243.77            1/1       Running   2          126d
kubernetes-dashboard-v1.4.1-gi2xr       1/1       Running   0          24d
tiller-deploy-3299276078-e8phb          1/1       Running   0          24d
#    
$ kubectl logs --namespace kube-system coredns-3558181428-0zhnh
2017/02/23 14:48:29 [INFO] Kubernetes middleware configured without a label selector. No label-based filtering will be performed.
.:53
2017/02/23 14:48:29 [INFO] CoreDNS-005
CoreDNS-005
10.2.6.127 - [23/Feb/2017:14:49:44 +0000] "AAAA IN kubernetes.default.svc.cluster.local. udp 54 false 512" NOERROR 107 544.128µs
10.2.6.127 - [23/Feb/2017:14:49:44 +0000] "MX IN kubernetes.default.svc.cluster.local. udp 54 false 512" NOERROR 107 7.576897ms
10.2.6.127 - [23/Feb/2017:14:49:52 +0000] "A IN kube-dns.kube-system.default.svc.cluster.local. udp 64 false 512" NXDOMAIN 117 471.176µs
23/Feb/2017:14:49:52 +0000 [ERROR 0 kube-dns.kube-system.default.svc.cluster.local. A] no items found
10.2.6.127 - [23/Feb/2017:14:50:00 +0000] "PTR IN 10.0.3.10.in-addr.arpa. udp 40 false 512" NOERROR 92 752.956µs
#    
$ kubectl logs --namespace kube-system coredns-3558181428-xri9i
2017/02/23 14:48:29 [INFO] Kubernetes middleware configured without a label selector. No label-based filtering will be performed.
.:53
2017/02/23 14:48:29 [INFO] CoreDNS-005
CoreDNS-005
10.2.6.127 - [23/Feb/2017:14:49:44 +0000] "A IN kubernetes.default.svc.cluster.local. udp 54 false 512" NOERROR 70 1.10732ms
10.2.6.127 - [23/Feb/2017:14:49:52 +0000] "A IN kube-dns.kube-system.svc.cluster.local. udp 56 false 512" NOERROR 72 409.74µs
10.2.6.127 - [23/Feb/2017:14:49:52 +0000] "AAAA IN kube-dns.kube-system.svc.cluster.local. udp 56 false 512" NOERROR 109 210.817µs
10.2.6.127 - [23/Feb/2017:14:49:52 +0000] "MX IN kube-dns.kube-system.svc.cluster.local. udp 56 false 512" NOERROR 109 796.703µs
10.2.6.127 - [23/Feb/2017:14:49:56 +0000] "PTR IN 1.0.3.10.in-addr.arpa. udp 39 false 512" NOERROR 89 694.649µs

DNS- ( ) log stdout Corefile.

: , Google Container Engine (GKE) - , kube-dns. , /.

CoreDNS Minikube


Kubernetes Minikube : addon manager ( ) , kube-dns. CoreDNS, .

, minikube:

$ minikube addons list
- dashboard: enabled
- default-storageclass: enabled
- kube-dns: enabled
- heapster: disabled
- ingress: disabled
- registry-creds: disabled
- addon-manager: enabled
$ minikube addons disable kube-dns
kube-dns was successfully disabled
$ minikube addons list
- heapster: disabled
- ingress: disabled
- registry-creds: disabled
- addon-manager: enabled
- dashboard: enabled
- default-storageclass: enabled
- kube-dns: disabled

CoreDNS Kubernetes (.. kubectl apply -f ). ReplicationController kube-dns, :

$ kubectl get -n kube-system pods
NAME                          READY     STATUS    RESTARTS   AGE
coredns-980047985-g2748       1/1       Running   1          36m
kube-addon-manager-minikube   1/1       Running   0          9d
kube-dns-v20-qzvr2            3/3       Running   0          1m
kubernetes-dashboard-ks1jp    1/1       Running   0          9d
$ kubectl delete -n kube-system rc kube-dns-v20
replicationcontroller "kube-dns-v20" deleted


CoreDNS — , ( SkyDNS), (Kubernetes Go), CNCF , , .

:



Source: https://habr.com/ru/post/J331872/

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