Hazelcast in SpringBoot Admin to run 2 instances via Docker Swarm

Question

I'm very new to SpringBoot Admin, HazelCast and Docker Swarm... What I'm trying to do is to run 2 instances of SpringBoot Admin Server, in Docker Swarm. It works fine with one instance. I have every feature of SBA working well. If I set the number of replicas to "2", with the following in swarm, then the logging in page doesn't work (it shows up but I can't log in, with no error in the console):

mode: replicated
      replicas: 2
      update_config:
        parallelism: 1
        delay: 60s
        failure_action: rollback
        order: start-first
        monitor: 60s
      rollback_config:
        parallelism: 1
        delay: 60s
        failure_action: pause
        order: start-first
        monitor: 60s
      restart_policy:
        condition: any
        delay: 60s
        max_attempts: 3
        window: 3600s

My current HazelCast config is the following (as specified in SpringBoot Admin doc):

@Bean
    public Config hazelcast() {
        // This map is used to store the events.
        // It should be configured to reliably hold all the data,
        // Spring Boot Admin will compact the events, if there are too many
        MapConfig eventStoreMap = new MapConfig(DEFAULT_NAME_EVENT_STORE_MAP).setInMemoryFormat(InMemoryFormat.OBJECT)
                .setBackupCount(1).setEvictionPolicy(EvictionPolicy.NONE)
                .setMergePolicyConfig(new MergePolicyConfig(PutIfAbsentMapMergePolicy.class.getName(), 100));

        // This map is used to deduplicate the notifications.
        // If data in this map gets lost it should not be a big issue as it will atmost
        // lead to
        // the same notification to be sent by multiple instances
        MapConfig sentNotificationsMap = new MapConfig(DEFAULT_NAME_SENT_NOTIFICATIONS_MAP)
                .setInMemoryFormat(InMemoryFormat.OBJECT).setBackupCount(1).setEvictionPolicy(EvictionPolicy.LRU)
                .setMergePolicyConfig(new MergePolicyConfig(PutIfAbsentMapMergePolicy.class.getName(), 100));

        Config config = new Config();
        config.addMapConfig(eventStoreMap);
        config.addMapConfig(sentNotificationsMap);
        config.setProperty("hazelcast.jmx", "true");

        // WARNING: This setups a local cluster, you change it to fit your needs.
        config.getNetworkConfig().getJoin().getMulticastConfig().setEnabled(true);
        TcpIpConfig tcpIpConfig = config.getNetworkConfig().getJoin().getTcpIpConfig();
        tcpIpConfig.setEnabled(true);

//        NetworkConfig network = config.getNetworkConfig();
//        InterfacesConfig interfaceConfig = network.getInterfaces();
//        interfaceConfig.setEnabled( true )
//                .addInterface( "192.168.1.3" );
//        tcpIpConfig.setMembers(singletonList("127.0.0.1"));
        return config;

    }
```

I guess these inputs are not enough for you to properly help, but since I don't really weel understand the way HazelCast is workging, I don't really know what is useful or not. So please don't hesitate to ask me for what is needed to help! :)

Do you guys have any idea of what I'm doing wrong?

Many thanks!

Could you paste the logs from your application (especially the logs from Hazelcast)? In general, I'm not sure that the following configuration is correct: `config.getNetworkConfig().getJoin().getMulticastConfig().setEnabled(true);`. Not sure that multicast works correctly in Docker Swarm. You can check out this community plugin: https://github.com/bitsofinfo/hazelcast-docker-swarm-discovery-spi — Rafał Leszko, Aug 24 '20 at 07:58
@RafałLeszko I will post the logs as soon as I reproduce the pb, next week I guess :) — John Student, Aug 26 '20 at 12:04

score 0 · Answer 1 · answered Aug 24 '20 at 19:37

0

Multicast is not working in Docker Swarm in default overlay driver (at least it stated here). I have tried to make it run with weave network plugin but without luck. In my case, it was enough to switch Hazelcast to the TCP mode and provide the network I like to search for the other replicas.

Something like that:

 -Dhz.discovery.method=TCP
 -Dhz.network.interfaces=10.0.251.*
 -Dhz.discovery.tcp.members=10.0.251.*

answered Aug 24 '20 at 19:37

Dmytro Sirant

118
10

Thanks for the answer! Where should I put this config exactly? In the application.yml ? – John Student Aug 26 '20 at 12:04
It should be a way to specify it somehow in the config. I believe it's somewhere here: // NetworkConfig network = config.getNetworkConfig(); // InterfacesConfig interfaceConfig = network.getInterfaces(); // interfaceConfig.setEnabled( true ) // .addInterface( "192.168.1.3" ); // tcpIpConfig.setMembers(singletonList("127.0.0.1")); – Dmytro Sirant Aug 27 '20 at 13:33

Hazelcast in SpringBoot Admin to run 2 instances via Docker Swarm

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