Introduction

• JS7 can be set up using a Kubernetes cluster on a Server. Using the Linux-based JS7 images for Docker® containers which ship with a current Alpine base image and OpenJDK.
• Docker® images for JS7 are publicly available from https://hub.docker.com/r/sosberlin/js7.
• Instructions on how to run containers for JS7 components can be found in the articles listed below.
• You can run an application by creating a Kubernetes Deployment object, and you can describe a Deployment in a YAML file. To do so we need to first install and set up the Kubernetes cluster, once it is completed you can use the deployment YAML files to deploy JS7.

Setting up a Kubernetes Cluster

There are several ways how to set up a Kubernetes Cluster. Find an example from the following chapters.

The basic step which can be followed to install the Kubernetes cluster on Centos are:

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Install Docker on all CentOS 7 VMs

1. Update the package database

   Code Block
   sudo yum check-update

2. Install the dependencies

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   sudo yum install -y yum-utils device-mapper-persistent-data lvm2

3. Add and enable the official Docker Repository to CentOS 7

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   sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

4. Install the latest Docker version on CentOS 7

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   sudo yum install docker-ce

5. A successful installation output will be concluded with a Complete!
You may be prompted to accept the GPG key. This is to verify that the fingerprint matches. The format will look as follows. If correct, accept it.

   Code Block
   060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35

6. Manage Docker service
   Now Docker is installed, but the service is not yet running. Start and enable Docker using the commands. 
   

   Code Block
   sudo systemctl start docker sudo systemctl enable docker

7. To confirm that Docker is active and running, use:
   

   Code Block
   sudo systemctl status docker

Set up the Kubernetes Repository

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Since the Kubernetes packages aren’t present in the official CentOS 7 repositories, we will need to add a new repository file. Use the following command to create the file and open it for editing:

sudo vi /etc/yum.repos.d/kubernetes.repo

Once the file is open, press the I key to enter insert mode and paste the following contents:

[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg

Once pasted, press escape to exit insert mode. Then enter :x to save the file and exit.

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Install Kubelet on CentOS 7

1. The first core module that we need to install on every node is Kubelet. Use the following command to do so:
   

   Code Block
   sudo yum install -y kubelet

Install kubeadm and kubectl on CentOS 7

kubeadm, the next core module, which has to be installed. Use the following command:

sudo yum install -y kubeadm

(Note that kubeadm automatically installs kubectl as a dependency)

Disable swap

For Kubelet to work, we also need to disable swap. The swap can be disabled using the below commands:

sudo swapoff -a
sudo sed -i '/ swap / s/^/#/' /etc/fstab

Initialize Kubeadm and start the Kubernetes cluster

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When we initialize the kubeadm directly, then the kubeadm throws the error:

Some fatal errors occurred: [ERROR CRI]: container runtime is not running Status from runtime service failed” err=”rpc error: code = Unimplemented desc = unknown service runtime.v1alpha2.RuntimeService”

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To resolve the above error, it is required to delete the config.tomal file and restart contained using the below steps:

sudo rm /etc/containerd/config.toml
systemctl restart containerd

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Initialize Kubeadm and Create required directories and start managing Kubernetes cluster

sudo kubeadm init
mkdir $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
export KUBECONFIG=/etc/kubernetes/admin.conf

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Enable and restart docker and Kubernetes services.

sudo systemctl enable docker.service
sudo service kubelet restart
sudo chown -R centos:centos kubernetes/

Set up Pod network for the Cluster.

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/2140ac876ef134e0ed5af15c65e414cf26827915/Documentation/kube-flannel.yml
kubectl get nodes

Following the above steps, the setup of the Kubernetes cluster is successful. Now you can create the Kubernetes YAML files and deploy the JS7 on this Kubernetes cluster.

Deploying JS7 on Kubernetes

The example YAML files of Kubernetes are attached to the article.

Download the attached zip file. The folder structure includes three files:

1. 1. js7-deployment.yaml – This file is the deployment file for the JS7

      Code Block
      language yml title Example js7-deployment.yaml linenumbers true collapse true
      apiVersion: v1 kind: Pod metadata: creationTimestamp: null labels: run: js7joc name: js7joc spec: volumes: - name: hibernate-config configMap: name: hibernate-config containers: - image: sosberlin/js7:joc-2-5-1 name: js7joc ports: - containerPort: 4446 volumeMounts: - name: hibernate-config mountPath: /var/sos-berlin.com/js7/joc/resources/joc/ env: - name: RUN_JS_JAVA_OPTIONS value: "-Xmx256m" - name: RUN_JS_USER_ID value: "0:0" - name: RUN_JS_ID value: "jobscheduler" - image: sosberlin/js7:controller-2-5-1 name: js7con ports: - containerPort: 4444 env: - name: RUN_JS_JAVA_OPTIONS value: "-Xmx256m" - name: RUN_JS_USER_ID value: "0:0" - name: RUN_JS_ID value: "jobscheduler" - image: sosberlin/js7:agent-2-5-1 name: js7agent ports: - containerPort: 4445

   2. js7-service.yaml – This includes the configuration of port forwarding

      Code Block
      language yml title Example js7-service.yaml linenumbers true collapse true
      apiVersion: v1 kind: Service metadata: creationTimestamp: null labels: run: js7joc name: js7joc spec: ports: - name: js7joc port: 4446 protocol: TCP targetPort: 4446 - name: js7agent port: 4445 protocol: TCP targetPort: 4445 - name: js7controller port: 4444 protocol: TCP targetPort: 4444 selector: run: js7joc type: LoadBalancer status: loadBalancer: {}

   3. hibernate.cfg.xml – This is the hibernate file for connection to the database.

      Code Block
      language yml title Example js7-service.yaml linenumbers true collapse true
      <?xml version="1.0" encoding="UTF-8" standalone="no"?> <hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">org.mysql.jdbc.Driver</property> <property name="hibernate.connection.password">jobscheduler</property> <property name="hibernate.connection.url">jdbc:mysql://mysqlsrv:3306/jobscheduler</property> <property name="hibernate.connection.username">jobscheduler</property> <property name="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</property> <property name="hibernate.show_sql">false</property> <property name="hibernate.connection.autocommit">false</property> <property name="hibernate.format_sql">true</property> <property name="hibernate.temp.use_jdbc_metadata_defaults">false</property> <property name="hibernate.connection.provider_class">org.hibernate.hikaricp.internal.HikariCPConnectionProvider</property> <property name="hibernate.hikari.maximumPoolSize">10</property> </session-factory> </hibernate-configuration>

To make the Kubernetes cluster run according to your database environment, you can adjust the hibernate.cfg.xml file with your database credentials. The default file is MySql. You can use the hibernate.cfg.xml files of the other database from JS7 - Database.

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