Context:

I am building an application and now I am on the infrastructure step.

The application is built with Java and persistence layer is MongoDB.

Problem:

If the application is running in same Node as persistence Layer are, everything goes ok, but on different nodes the application cannot communicate with MongoDB.

There is a print of Kubernetes Dashboard:

As you can see, two pods of application (gateway) are running in same node as Mongo, but other two don't. These two are not finding MongoDb.

Here is the mongo-db.yaml:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mongo-data
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  hostPath:
    path: /home/vitor/seguranca/mongo

---

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc
spec:
  storageClassName: ""
  accessModes:
    - ReadWriteOnce 
  volumeName: mongo-data
  resources:
    requests:
      storage: 1Gi

---

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: mongo
  name: mongo

spec:
  replicas: 1
  selector:
    matchLabels:
      app: mongo
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: mongo
      name: mongo-service

    spec:
      volumes:
      - name: "deployment-storage"
        persistentVolumeClaim:
          claimName: "pvc"

      containers:
      - image: mongo
        name: mongo
        ports:
          - containerPort: 27017
        volumeMounts:
          - name: "deployment-storage"
            mountPath: "/data/db"
        
status: {}
---

apiVersion: v1
kind: Service
metadata:
  labels:
    app: mongo
  name: mongo-service
spec:
  ports:
  - port: 27017
    targetPort: 27017
  selector:
    app: mongo
  clusterIP: None

and here the application.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: gateway
  name: gateway
spec:
  replicas: 4
  selector:
    matchLabels:
      app: gateway
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: gateway
    spec:
      containers:

      - image: vitornilson1998/native-micro
        name: native-micro
        env:
        - name: MONGO_CONNECTION_STRING
          value: mongodb://mongo-service:27017 #HERE IS THE POINT THAT THE APPLICATION USES TO ACCESS MONGODB
        - name: MONGO_DB
          value: gateway
        resources: {}
        ports:
          - containerPort: 8080
        
status: {}

---

apiVersion: v1
kind: Service
metadata:
  creationTimestamp: null
  labels:
    app: gateway-service
  name: gateway-service
spec:
  ports:
  - name: 8080-8080
    port: 8080
    protocol: TCP
    targetPort: 8080
  selector:
    app: gateway
  type: NodePort
status:
  loadBalancer: {}

I can't see what is stopping application to reach MongoDB.

Should I do what?

CodePudding user response：

I was using calico as CNI.

I removed calico and let kube-proxy take care of everything.

Now everything is working fine.