Hazelcast and Springboot on Kubernetes

Hello Everyone, In last post we have seen how to build distributed cache as a spring boot application.

Today we are going to deploy that application to kubernetes.

Why Kubernetes?

Hazelcast is a In-memory data grid solution where that idea is to distribute data across many nodes inside a cluster. Kubernetes is an ideal solution to run such an environment on cloud platform as you can easily scale up and scale down the number of running instances.

Architecture

Now, we want to run such multiple spring boot application on Kubernetes.

Each of spring boot application exposes port 8080 for http access and 5701 Hazelcast cluster members discovery. Each of the hazelcast instace is embedded into spring boot application.

In the above architecture, we have exposed hospital service via 8080 for http access and we have also exposed hazelcast servie for enabling discovery between Hazelcast instances via 5701.

Implmentation

From previous post, will start making changes to the code.

We will have to add kubernetes dependencies. Below is the pom file after changes.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.rbitcs</groupId>
<artifactId>doctors</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>doctors</name>
<description>Spring Boot Application with hazelcast</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast</artifactId>
</dependency>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>spring-data-hazelcast</artifactId>
<version>2.2.2</version>
</dependency>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast-spring</artifactId>
</dependency>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast-client</artifactId>
</dependency>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast-kubernetes</artifactId>
<version>1.5.2</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

Now, we have to disable multicast discovery, which is enabled by default and enable discovery through Kubernetes as below.

@Bean Config config() {    Config config = new Config();    config.getNetworkConfig().getJoin().getTcpIpConfig().setEnabled(false);    config.getNetworkConfig().getJoin().getMulticastConfig().setEnabled(false);    config.getNetworkConfig().getJoin().getKubernetesConfig().setEnabled(true)          .setProperty("namespace", "default")          .setProperty("service-name", "hazelcast-service");    return config; }

Next we have to define Doctor service on 5701 as k8s service. This is referred to Doctor Service.

apiVersion: v1 
kind: Service 
metadata:   
   name: hazelcast-service 
spec:   
   selector:     
     app: doctor-service   
   ports:     
     - name: hazelcast       
       port: 5701   
   type: LoadBalancer

We have to set up kubernetes deployment and service definition. From our architecture we are setting up 3 replicas for our deployment, which are exposed out of continers with 2 ports 8080 and 5701.

Below is the deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: doctor-service
  labels:
    app: doctor-service
spec:
  replicas: 3
  selector:
    matchLabels:
      app: doctor-service
  template:
    metadata:
      labels:
        app: doctor-service
    spec:
      containers:
        - name: doctor-service
          image: rbitcs/doctor-service
          ports:
            - name: http
              containerPort: 8080
            - name: multicast
              containerPort: 5701
---
apiVersion: v1
kind: Service
metadata:
  name: doctor-service
  labels:
    app: doctor-service
spec:
  ports:
    - port: 8080
      protocol: TCP
  selector:
    app: doctor-service
  type: NodePort

That’s all with the changes.

Lets run hazelcast on Kubernetes via Minikube

$ minikube start --vm-driver=virtualbox
$ skaffold dev

Since we defined 3 replicas, after successful start up we should see three fragment of pods logs printed out by Skaffold

list of services HTTP API is available outside Minikube

The deployment.yaml can be changed as desired state is required. This is how scability can be achieved.

Please take a look at github for complete code.