Access internal database in cluster with local application

Question

I try to connect a local spring boot application with an internal mysql-db in k8-cluster. I used the k8 cluster locally in docker desktop.

My deployment.yml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kazi-db
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
        - image: mysql/mysql-server:8.0
          name: mysql
          imagePullPolicy: IfNotPresent
          env:
            - name: MYSQL_ROOT_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: kazi-db-secret
                  key: password
          ports:
            - containerPort: 3306
              name: mysql
          volumeMounts:
            - name: mysql-persistent-storage
              mountPath: /var/lib/mysql
      volumes:
        - name: mysql-persistent-storage
          persistentVolumeClaim:
            claimName: mysql-pv-claim
        - name: mysql-initdb
          configMap:
            name: kazi-initdb

my service.yml:

apiVersion: v1
kind: Service
metadata:
  name: kazi-db
spec:
  ports:
    - port: 3306
  selector:
    app: kazi-db
  type: LoadBalancer

The service description:

kubectl get services kazi-db     
NAME      TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kazi-db   LoadBalancer   10.107.75.107   localhost     3306:31627/TCP   3d

my spring-boot application.yml

## JDBC part
spring:
  config:
    activate:
      on-profile: local
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/kazi?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
    username: emo
    password: 123qwe
  jpa:
    show-sql: true
    database-platform: org.hibernate.dialect.MySQL8Dialect
    hibernate:
      ddl-auto: update
  liquibase:
    change-log: classpath:liquibase/changelog.xml

I used localhost because k8 has a localhost as externalIp defined.

kubectl describe services kazi-db
Name:                     kazi-db
Namespace:                default
Labels:                   <none>
Annotations:              <none>
Selector:                 app=kazi-db
Type:                     LoadBalancer
IP Families:              <none>
IP:                       10.107.75.107
IPs:                      <none>
LoadBalancer Ingress:     localhost
Port:                     <unset>  3306/TCP
TargetPort:               3306/TCP
NodePort:                 <unset>  31627/TCP
Endpoints:                <none>
Session Affinity:         None
External Traffic Policy:  Cluster
Events:
  Type    Reason  Age   From                Message
  ----    ------  ----  ----                -------
  Normal  Type    10m   service-controller  ClusterIP -> LoadBalancer    

I have a local mysql-db too an i can connect the application without problems. I can connect to the db-cluster with kubectl exec -it kazi-db-554bd6d787-2gb88 -- /bin/bash an create some table, but the application not.

When i start the spring-boot application:

java.sql.SQLSyntaxErrorException: Unknown database 'kazi'
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.18.jar:8.0.18]

although the db kazi exists in db-cluster.

But how i have to connect to internal k8 cluster db?

I'm using docker desktop v20.10.11 with k8s v1.22.4. I tried it with minikube version: v1.24.0 too. Of both, i have the same issue.

Answer 1

i resolve it with port forwarding: kubectl port-forward <pod-name> 3306:3306 -n default