无法连接到 Kubernetes 中的 Cockroach pod

Question

我正在开发一个带有网络服务和持久层的简单网络应用程序。 Web 持久层是 Cockroach db。我正在尝试使用单个命令部署我的应用程序：

kubectl apply -f my-app.yaml

应用部署成功。但是，当后端必须在数据库中存储某些内容时，会出现以下错误：

dial tcp: lookup web-service-cockroach on 192.168.65.1:53: no such host

当我启动我的应用程序时，我向 cockroach 数据库提供了以下连接字符串并且连接成功，但是当我尝试在数据库中存储某些内容时出现上述错误：

postgresql://root@web-service-db:26257/defaultdb?sslmode=disable

出于某种原因，web pod 无法与 db pod 通信。我的整个配置是：


# Service for web application
apiVersion: v1
kind: Service
metadata:
name: web-service
spec:
selector:
 app: web-service
type: NodePort
ports:
 - protocol: TCP
   port: 8080
   targetPort: http
   nodePort: 30103
externalIPs:
 - 192.168.1.9    # < - my local ip
---

# Deployment of web app
apiVersion: apps/v1
kind: Deployment
metadata:
name: web-service
spec:
selector:
 matchLabels:
   app: web-service
replicas: 1
template:
 metadata:
   labels:
     app: web-service
 spec:
   hostNetwork: true
   containers:
     - name: web-service
       image: my-local-img:latest
       imagePullPolicy: IfNotPresent
       ports:
         - name: http
           containerPort: 8080
           hostPort: 8080
       env:
         - name: DB_CONNECT_STRING
           value: "postgresql://root@web-service-db:26257/defaultdb?sslmode=disable"

---
### Kubernetes official doc PersistentVolume
apiVersion: v1
kind: PersistentVolume
metadata:
name: cockroach-pv-volume
labels:
 type: local
spec:
storageClassName: manual
capacity:
 storage: 10Gi
accessModes:
 - ReadWriteOnce
hostPath:
 path: "/tmp/my-local-volueme"

---
### Kubernetes official doc PersistentVolumeClaim
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: cockroach-pv-claim
spec:
storageClassName: manual
accessModes:
 - ReadWriteOnce
resources:
 requests:
   storage: 4Gi
---

# Cockroach used by web-service
apiVersion: v1
kind: Service
metadata:
name: web-service-cockroach
labels:
 app: web-service-cockroach
spec:
selector:
 app: web-service-cockroach
type: NodePort
ports:
 - protocol: TCP
   port: 26257
   targetPort: 26257
   nodePort: 30104
---

# Cockroach stateful set used to deploy locally
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: web-service-cockroach
spec:
serviceName: web-service-cockroach
replicas: 1
selector:
 matchLabels:
   app: web-service-cockroach
template:
 metadata:
   labels:
     app: web-service-cockroach
 spec:
   volumes:
     - name: cockroach-pv-storage
       persistentVolumeClaim:
         claimName: cockroach-pv-claim
   containers:
     - name: web-service-cockroach
       image: cockroachdb/cockroach:latest
       command:
         - /cockroach/cockroach.sh
         - start
         - --insecure
       volumeMounts:
         - mountPath: "/tmp/my-local-volume"
           name: cockroach-pv-storage
       ports:
         - containerPort: 26257

部署后一切正常。

kubectl get service
NAME                      TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)           AGE
kubernetes               ClusterIP   10.96.0.1      <none>        443/TCP           50m
web-service              NodePort    10.111.85.64   192.168.1.9   8080:30103/TCP    6m17s
webs-service-cockroach   NodePort    10.96.42.121   <none>        26257:30104/TCP   6m8s

kubectl get pods
NAME                                  READY   STATUS    RESTARTS   AGE
web-service-6cc74b5f54-jlvd6   1/1     Running   0          24m
web-service-cockroach-0        1/1     Running   0          24m

提前致谢！

Answer 1

看来您的 DNS 有问题。

dial tcp: lookup web-service-cockroach on 192.168.65.1:53: no such host

地址192.168.65.1不喜欢kube-dns服务ip。

如果您在使用主机网络的地方可以解释这一点，而且令人惊讶的是您确实这样做了。使用 hostNetwork: true 时，默认使用的 dns 服务器是主机使用的服务器，绝不会是 kube-dns。

要解决它设置：

spec:
  dnsPolicy: ClusterFirstWithHostNet

它将dns服务器设置为pod的k8s服务器。

查看 kubernetes 文档以获取有关 Pod's DNS Policy 的更多信息。

无法连接到 Kubernetes 中的 Cockroach pod

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