kubernetes DNS Pod 名称解析

Question

我正在尝试在我的 EKS Kubernetes 集群 v1.10.3 上使用 dns pod 名称解析。我的理解是，创建 headless 服务将创建我需要的必要的 pod 名称记录，但我发现这不是真的。我错过了什么吗？

也欢迎其他关于如何实现这一目标的想法。找不到替代解决方案。

添加更新

我还不够清楚。本质上我需要的是这样解决: worker -767cd94c5c-c5bq7 -> 10.0.10.10 worker -98dcd94c5d-cabq6 -> 10.0.10.11等等......

我真的不需要循环 DNS，只需在某处读到这可能是一个解决方法。谢谢!

# my service
apiVersion: v1
kind: Service
metadata:
  ...
  name: worker
  namespace: airflow-dev
  resourceVersion: "374341"
  selfLink: /api/v1/namespaces/airflow-dev/services/worker
  uid: 814251ac-acbe-11e8-995f-024f412c6390
spec:
  clusterIP: None
  ports:
  - name: worker
    port: 8793
    protocol: TCP
    targetPort: 8793
  selector:
    app: airflow
    tier: worker
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}





# my pod
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: 2018-08-31T01:39:37Z
  generateName: worker-69887d5d59-
  labels:
    app: airflow
    pod-template-hash: "2544381815"
    tier: worker
  name: worker-69887d5d59-6b6fc
  namespace: airflow-dev
  ownerReferences:
  - apiVersion: extensions/v1beta1
    blockOwnerDeletion: true
    controller: true
    kind: ReplicaSet
    name: worker-69887d5d59
    uid: 16019507-ac6b-11e8-995f-024f412c6390
  resourceVersion: "372954"
  selfLink: /api/v1/namespaces/airflow-dev/pods/worker-69887d5d59-6b6fc
  uid: b8d82a6b-acbe-11e8-995f-024f412c6390
spec:
  containers:
  ...
  ...
    name: worker
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
      ...
      ...
  dnsPolicy: ClusterFirst
  nodeName: ip-10-0-1-226.us-west-2.compute.internal
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: airflow
  serviceAccountName: airflow
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
    ...
    ...
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2018-08-31T01:39:37Z
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: 2018-08-31T01:39:40Z
    status: "True"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: 2018-08-31T01:39:37Z
    status: "True"
    type: PodScheduled
  containerStatuses:
  ...
  ...
    lastState: {}
    name: worker
    ready: true
    restartCount: 0
    state:
      running:
        startedAt: 2018-08-31T01:39:39Z
  hostIP: 10.0.1.226
  phase: Running
  podIP: 10.0.1.234
  qosClass: BestEffort
  startTime: 2018-08-31T01:39:37Z





# querying the service dns record works!
airflow@worker-69887d5d59-6b6fc:~$ nslookup worker.airflow-dev.svc.cluster.local
Server:   172.20.0.10
Address:  172.20.0.10#53

Name: worker.airflow-dev.svc.cluster.local
Address: 10.0.1.234





# querying the pod name does not work :(
airflow@worker-69887d5d59-6b6fc:~$ nslookup worker-69887d5d59-6b6fc.airflow-dev.svc.cluster.local
Server:   172.20.0.10
Address:  172.20.0.10#53

** server can't find worker-69887d5d59-6b6fc.airflow-dev.svc.cluster.local: NXDOMAIN

airflow@worker-69887d5d59-6b6fc:~$ nslookup worker-69887d5d59-6b6fc.airflow-dev.pod.cluster.local
Server:   172.20.0.10
Address:  172.20.0.10#53

*** Can't find worker-69887d5d59-6b6fc.airflow-dev.pod.cluster.local: No answer

Answer 1

在内部，我建议使用服务 DNS 记录来指向 Pod，您已经确认该记录有效。这当然不需要您有 Headless 服务来使用服务 DNS。

kube-dns 自动记录的工作方式如下:

pod -> 同一命名空间中的服务:curl http://servicename

pod -> 不同命名空间中的服务:curl http://servicename.namespace

在此处了解有关服务发现的更多信息:https://kubernetes.io/docs/concepts/services-networking/service/#environment-variables

您可以在此处阅读有关服务的 DNS 记录的更多信息 https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#services

如果您需要外部自定义名称解析，我建议使用 nginx-ingress:

https://github.com/helm/charts/tree/master/stable/nginx-ingress https://github.com/kubernetes/ingress-nginx

编辑:包括有关实际 Pod DNS 的详细信息

v1.2 引入了一个 beta 功能，用户可以指定 Pod 注释 pod.beta.kubernetes.io/subdomain 来指定 Pod 的子域。最终域名将是“...svc.”。例如，主机名注释设置为“foo”、子域注释设置为“bar”、命名空间“my-namespace”中的 Pod 将具有 FQDN“foo.bar.my-namespace.svc.cluster”。本地”

A Records and hostname based on Pod's hostname and subdomain fields Currently when a pod is created, its hostname is the Pod's metadata.name value.

With v1.2, users can specify a Pod annotation, pod.beta.kubernetes.io/hostname, to specify what the Pod's hostname should be. The Pod annotation, if specified, takes precedence over the Pod's name, to be the hostname of the pod. For example, given a Pod with annotation pod.beta.kubernetes.io/hostname: my-pod-name, the Pod will have its hostname set to "my-pod-name".

With v1.3, the PodSpec has a hostname field, which can be used to specify the Pod's hostname. This field value takes precedence over the pod.beta.kubernetes.io/hostname annotation value.

v1.2 introduces a beta feature where the user can specify a Pod annotation, pod.beta.kubernetes.io/subdomain, to specify the Pod's subdomain. The final domain will be "...svc.". For example, a Pod with the hostname annotation set to "foo", and the subdomain annotation set to "bar", in namespace "my-namespace", will have the FQDN "foo.bar.my-namespace.svc.cluster.local"

With v1.3, the PodSpec has a subdomain field, which can be used to specify the Pod's subdomain. This field value takes precedence over the pod.beta.kubernetes.io/subdomain annotation value.

https://unofficial-kubernetes.readthedocs.io/en/latest/concepts/services-networking/dns-pod-service/