Styjun

I have three different images related to my application which works fine in docker-compose and has issues running on kubernetes cluster in GCP.

Below is the deployment file.

apiVersion: v1
kind: Service
metadata:
 name: mysql
 labels:
 app: mysql-database
spec:
 type: NodePort
 ports:
 - port: 3306
 targetPort: 3306 
 selector:
 app: mysql-database
 tier: database
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
 name: mysql
 labels:
 app: mysql-database
spec:
 strategy:
 type: Recreate
 template:
 metadata:
 labels:
 app: mysql-database
 tier: database
 spec:
 hostname: mysql
 containers:
 - image: mysql/mysql-server:5.7
 name: mysql
 env:
 - name: "MYSQL_USER"
 value: "root"
 - name: "MYSQL_HOST"
 value: "mysql"
 - name: "MYSQL_DATABASE"
 value: "xxxx"
 - name: "MYSQL_PORT"
 value: "3306"
 - name: "MYSQL_PASSWORD"
 value: "password"
 - name: "MYSQL_ROOT_PASSWORD"
 value: "password"
 - name: "RAILS_ENV"
 value: "production"
 ports:
 - containerPort: 5432
 name: db
---
apiVersion: v1
kind: Service
metadata:
 name: dgservice
 labels:
 app: dgservice
spec:
 type: NodePort
 ports:
 - port: 8080
 targetPort: 8080
 selector:
 name: dgservice
 tier: dgservice
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
 name: dgservice
 labels:
 app: dgservice
spec:
 strategy:
 type: Recreate
 template:
 metadata:
 labels:
 app: dgservice
 tier: dgservice
 spec:
 hostname: dgservice
 containers:
 - image: gcr.io/sample/sample-image:check_1
 name: dgservice
 ports:
 - containerPort: 8080
 name: dgservice
---
apiVersion: v1
kind: Service
metadata:
 name: dg-ui
 labels:
 name: dg-ui
spec:
 type: NodePort
 ports:
 - nodePort: 30156 
 port: 8000
 protocol: TCP
 targetPort: 8000
 selector:
 app: dg-ui
 tier: dg
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
 name: dg-ui
 labels:
 app: dg-ui
spec:
 strategy:
 type: Recreate
 template:
 metadata:
 labels:
 app: dg-ui
 tier: dg
 spec:
 hostname: dg-ui
 containers:
 - image: gcr.io/sample/sample:latest
 name: dg-ui
 env:
 - name: "MYSQL_USER"
 value: "root"
 - name: "MYSQL_HOST"
 value: "mysql"
 - name: "MYSQL_DATABASE"
 value: "xxxx"
 - name: "MYSQL_PORT"
 value: "3306"
 - name: "MYSQL_PASSWORD"
 value: "password"
 - name: "MYSQL_ROOT_PASSWORD"
 value: "password"
 - name: "RAILS_ENV"
 value: "production"
 - name: "DG_SERVICE_HOST"
 value: "dgservice"
 ports:
 - containerPort: 8000
 name: dg-ui

The image is being pulled successfully from GCR as well.

The connection between mysql and ui service also works fine and my data's are getting migrated without any issues. But the connection is not established between the service and the ui.

Why ui is not able to access service in my application?

As your deployment has the following lables so service need to have same labels in order to create endpoint object

endpoints are the API object behind a service. The endpoints are where a service will route connections to when a connection is made to the ClusterIP of a service

Following are the labels of deployments

 labels:
 app: dgservice
 tier: dgservice

New Service definition with correct labels

apiVersion: v1
kind: Service
metadata:
 name: dgservice
 labels:
 app: dgservice
spec:
 type: NodePort
 ports:
 - port: 8080
 targetPort: 8080
 selector:
 app: dgservice
 tier: dgservice

I am assuming by "service" you are referring to your "dgservice". With the yaml presented above, I believe you also need to specify the DG_SERVICE_PORT (port 8080) to correctly access "dgservice".

As mentioned by Suresh in the comments, you should expose internal services using ClusterIP type. The NodePort is a superset of ClusterIP, and will expose the service internally to your cluster at service-name:port, and externally at node-ip:nodeport, targeting your deployment/pod at targetport.