Replicate Data between Two Hazelcast Clusters with Hazelcast Platform Operator

Learn how to keep data in sync across two Hazelcast clusters.

Context

In this tutorial, you’ll do the following:

Deploy two Hazelcast clusters.
Create two Hazelcast map configurations on one of the clusters.
Synchronize map data between the two Hazelcast clusters.

Before you Begin

Before starting this tutorial, make sure that you have the following:

A running Kubernetes cluster
The Kubernetes command-line tool, kubectl
A deployed Hazelcast Platform Operator

Step 1. Start the Hazelcast Cluster

Clone the examples repository

git clone https://github.com/hazelcast-guides/hazelcast-platform-operator-wan-replication.git
cd hazelcast-platform-operator-wan-replication

The sample code(excluding CLC) for this tutorial is in the clients directory.

Create a secret with your Hazelcast Enterprise License.

kubectl create secret generic hazelcast-license-key --from-literal=license-key=<hz-license-key>

Create the Hazelcast clusters.

Run the following command to create the first cluster.

cat <<EOF | kubectl apply -f -
apiVersion: hazelcast.com/v1alpha1
kind: Hazelcast
metadata:
  name: hazelcast-first
spec:
  licenseKeySecret: hazelcast-license-key
  exposeExternally:
    type: Unisocket
    discoveryServiceType: LoadBalancer
EOF

Run the following command to create the second cluster.

cat <<EOF | kubectl apply -f -
apiVersion: hazelcast.com/v1alpha1
kind: Hazelcast
metadata:
  name: hazelcast-second
spec:
  licenseKeySecret: hazelcast-license-key
  exposeExternally:
    type: Unisocket
    discoveryServiceType: LoadBalancer
EOF

Check the status of the clusters to make sure that both clusters are running.

kubectl get hazelcast

NAME               STATUS    MEMBERS
hazelcast-first    Running   3/3
hazelcast-second   Running   3/3

Find the addresses of the clusters.

kubectl get hazelcastendpoint --selector="app.kubernetes.io/instance in (hazelcast-first, hazelcast-second)"

NAME                   TYPE        ADDRESS
hazelcast-first        Discovery   34.123.9.149:5701
hazelcast-first-wan    WAN         34.123.9.149:5710
hazelcast-second       Discovery   34.16.0.16:5701
hazelcast-second-wan   WAN         34.16.0.16:5710

The ADDRESS column displays the external addresses of the Hazelcast clusters.

Step 2. Create a WAN Replication Configuration

Create two maps on the first cluster. In this example, the following maps are created:

map-1

map-2.

cat <<EOF | kubectl apply -f -
apiVersion: hazelcast.com/v1alpha1
kind: Map
metadata:
  name: map-1
spec:
  hazelcastResourceName: hazelcast-first
---
apiVersion: hazelcast.com/v1alpha1
kind: Map
metadata:
  name: map-2
spec:
  hazelcastResourceName: hazelcast-first
EOF

Create the configuration for WAN replication:
- Use the first cluster as the source cluster by adding its name as a resource in the WAN Replication configuration. Adding the cluster name as a resource starts WAN replication for both the maps that you created earlier.
- Add the second cluster as the target cluster to receive the WAN Replication events.
  
  Run the following command to apply the configuration.
  cat <<EOF | kubectl apply -f - apiVersion: hazelcast.com/v1alpha1 kind: WanReplication metadata: name: wan-replication spec: resources: - name: hazelcast-first kind: Hazelcast targetClusterName: dev endpoints: "<SECOND-CLUSTER-EXTERNAL-IP>" EOF

Step 3. Put Entries to the Maps on the First Cluster

In this step, you’ll fill the maps on the first, source cluster.

Configure the Hazelcast client to connect to the first cluster, using its address.

CLC
Java
NodeJS
Go
Python
.NET

Before using CLC, it should be installed in your system. Check the installation instructions for CLC: Installing the Hazelcast CLC.

Run the following command for adding the first cluster config to the CLC.

clc config add hz-1 cluster.name=dev cluster.address=<FIRST-CLUSTER-EXTERNAL-IP>

ClientConfig config = new ClientConfig();
config.getNetworkConfig().addAddress("<FIRST-CLUSTER-EXTERNAL-IP>");

const { Client } = require('hazelcast-client');

const clientConfig = {
    network: {
        clusterMembers: [
            '<FIRST-CLUSTER-EXTERNAL-IP>'
        ]
    }
};
const client = await Client.newHazelcastClient(clientConfig);

import (
	"log"

	"github.com/hazelcast/hazelcast-go-client"
)

func main() {
	config := hazelcast.Config{}
	cc := &config.Cluster
	cc.Network.SetAddresses("<FIRST-CLUSTER-EXTERNAL-IP>")
	ctx := context.TODO()
	client, err := hazelcast.StartNewClientWithConfig(ctx, config)
	if err != nil {
		panic(err)
	}
}

import logging
import hazelcast

logging.basicConfig(level=logging.INFO)

client = hazelcast.HazelcastClient(
    cluster_members=["<FIRST-CLUSTER-EXTERNAL-IP>"],
    use_public_ip=True,
)

var options = new HazelcastOptionsBuilder()
    .With(args)
    .With((configuration, options) =>
    {
        options.Networking.UsePublicAddresses = true;
        options.Networking.SmartRouting = false;
        options.Networking.Addresses.Add("<FIRST-CLUSTER-EXTERNAL-IP>");
    })
    .Build();

Start to fill the maps.

CLC
Java
NodeJS
Go
Python
.NET

Run the following command for each map, using the map name as an argument to fill each map with entries. Use the map names map-1 and map-2.

for i in {1..10};
do
   clc -c hz-1 map set --name <MAP-NAME> key-$i value-$i;
done

Run the following command for each map to check if the sizes are expected.

clc -c hz-1 map size --name <MAP-NAME>

Start the application for each map, using the map name as an argument to fill each map with random entries. Use the map names map-1 and map-2.

cd clients/java
mvn package
java -jar target/*jar-with-dependencies*.jar fill <MAP-NAME>