We are deploying a spring-boot application using spring-session-hazelcast + hazelcast-kubernetes on an OpenShift/Kubernetes cluster.

Due to the nature of our platform, we can only use service-dns configuration. We expose a service on port 5701 for multicasting and set service-dns property to the multicast service name.

Below is a snippet for creation of the Hazelcast instance.

@Bean
public HazelcastInstance hazelcastInstance() {
    var config = new Config();
    config.setClusterName("spring-session-cluster");

    var join = config.getNetworkConfig().getJoin();
    join.getTcpIpConfig().setEnabled(false);
    join.getMulticastConfig().setEnabled(false);
    join.getKubernetesConfig().setEnabled(true)
                .setProperty("service-dns", "<multicast-service-name>");

    var attribute = new AttributeConfig()
                .setName(Hazelcast4IndexedSessionRepository.PRINCIPAL_NAME_ATTRIBUTE)
                .setExtractorClassName(Hazelcast4PrincipalNameExtractor.class.getName());

    config.getMapConfig(Hazelcast4IndexedSessionRepository.DEFAULT_SESSION_MAP_NAME)
                .addAttributeConfig(attribute)
                .addIndexConfig(new IndexConfig(IndexType.HASH, Hazelcast4IndexedSessionRepository.PRINCIPAL_NAME_ATTRIBUTE));

    var serializer = new SerializerConfig();
    serializer.setImplementation(new HazelcastSessionSerializer())
        .setTypeClass(MapSession.class);
    config.getSerializationConfig().addSerializerConfig(serializer);

    return Hazelcast.newHazelcastInstance(config);
}

When we run 2 pods for this application, we see the below ERROR log:

com.hazelcast.internal.cluster.impl.operations.SplitBrainMergeValidationOp
Message: [<private-ip>]:5701 [spring-session-cluster] [4.2] Target is this node! -> [<private-ip>]:5701

Can someone please explain how to fix this error, still using "service-dns" configuration?