Using spring-session-hazelcast on Kubernetes with service-dns causing SplitBrainMergeValidationOp ERROR

user_931224 0
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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?

spring-session hazelcast spring-boot kubernetes
2 Answers
user_28000890

Just add configuration for split brain protection

SplitBrainProtectionConfig splitBrainProtectionConfig = new SplitBrainProtectionConfig();
    splitBrainProtectionConfig.setName("splitBrainProtectionRuleWithFourMembers")
                    .setEnabled(true)
                    .setMinimumClusterSize(4);

    MapConfig mapConfig = new MapConfig();
    mapConfig.setSplitBrainProtectionName("splitBrainProtectionRuleWithFourMembers");

    Config config = new Config();
    config.addSplitBrainProtectionConfig(splitBrainProtectionConfig);
    config.addMapConfig(mapConfig);

You can read more about this in hazelcast documentation: https://docs.hazelcast.com/imdg/4.2/network-partitioning/split-brain-protection.html

user_90568340
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