Kubernetes Application – Package Multiple Resources Together

Deploying an application in Kubernetes require to create multiple resources such as Pods, Services, Replication Controllers, and others. Typically each resource is define in a configuration file and created using kubectl script. But if multiple resources need to be created then you need to invoke kubectl multiple times. So if you need to create the following resources:

• MySQL Pod
• MySQL Service
• WildFly Replication Controller

Then the commands would look like:

kubectl.sh create -f ~/workspaces/kubernetes-java-sample/app-mysql-pod.yaml
kubectl.sh create -f ~/workspaces/kubernetes-java-sample/app-mysql-service.yaml
kubectl.sh create -f ~/workspaces/kubernetes-java-sample/app-wildfly-rc.yaml

Or for convenience, wrap these invocations in a shell script. But that is not very intuitive! There is a better, and more natural and intuitive way.

Kubernetes allow multiple resources to be specified in a single configuration file. This allows to create a “Kubernetes Application” that can consists of multiple resources easily.

Previous section showed how to deploy the Java EE application using multiple configuration files. This application can be delpoyed using a single configuration file as well.

An application, as discussed above, consisting of MySQL Pod, MySQL Service, and WildFly Replication Controller can be created using the following configuration file:

apiVersion: v1
kind: Pod
metadata:
  name: mysql-pod
  labels:
    name: mysql-pod
    context: docker-k8s-lab
spec:
  containers:
    -
      name: mysql
      image: mysql:latest
      env:
        -
          name: "MYSQL_USER"
          value: "mysql"
        -
          name: "MYSQL_PASSWORD"
          value: "mysql"
        -
          name: "MYSQL_DATABASE"
          value: "sample"
        -
          name: "MYSQL_ROOT_PASSWORD"
          value: "supersecret"
      ports:
        -
          containerPort: 3306
----
apiVersion: v1
kind: Service
metadata:
  name: mysql-service
  labels:
    name: mysql-pod
    context: docker-k8s-lab
spec:
  ports:
    # the port that this service should serve on
    - port: 3306
  # label keys and values that must match in order to receive traffic for this service
  selector:
    name: mysql-pod
    context: docker-k8s-lab
----
apiVersion: v1
kind: ReplicationController
metadata:
  name: wildfly-rc
  labels:
    name: wildfly
    context: docker-k8s-lab
spec:
  replicas: 1
  template:
    metadata:
      labels:
        name: wildfly
    spec:
      containers:
      - name: wildfly-rc-pod
        image: arungupta/wildfly-mysql-javaee7:k8s
        ports:
        - containerPort: 8080

Notice that each section, one each for MySQL Pod, MySQL Service, and WildFly Replication Controller, is separated by ----.

kubectl.sh create -f ~/workspaces/kubernetes-java-sample/app.yaml
pods/mysql-pod
services/mysql-service
replicationcontrollers/wildfly-rc