Question

我们在客户端 - 服务器模式下使用hazelcast。 hazelcast集群包含2个hazelcast节点，我们有大约25个客户端连接到集群。

我现在正在寻找的是一个简单的检查，试图找出群集是否还活着。它应该是一个相当便宜的操作，因为这种检查会经常发生在每个客户端上（我可以想象每秒一次）。

最好的方法是什么？

Answer 1

最简单的方法是将LifecycleListener注册到客户端HazelcastInstance：

    HazelcastInstance client = HazelcastClient.newHazelcastClient();
    client.getLifecycleService().addLifecycleListener(new LifecycleListener() {
        @Override
        public void stateChanged(LifecycleEvent event) {

        }
    })

客户端使用定期心跳来检测群集是否仍在运行。

Answer 2

您也可以使用LifecycleService.isRunning()方法：

HazelcastInstance hzInstance = HazelcastClient.newHazelcastClient();
hzInstance.getLifecycleService().isRunning()

Answer 3

我找到了一种更可靠的方法来检查hazelcast的可用性，因为

client.getLifecycleService().isRunning()

当您使用异步重新连接模式时，总是返回true，如上所述。

@Slf4j
public class DistributedCacheServiceImpl implements DistributedCacheService {

    private HazelcastInstance client;

    @Autowired
    protected ConfigLoader<ServersConfig> serversConfigLoader;

    @PostConstruct
    private void initHazelcastClient() {
        ClientConfig config = new ClientConfig();
        if (isCacheEnabled()) {
            ServersConfig.Hazelсast hazelcastConfig = getWidgetCacheSettings().getHazelcast();
            config.getGroupConfig().setName(hazelcastConfig.getName());
            config.getGroupConfig().setPassword(hazelcastConfig.getPassword());
            for (String address : hazelcastConfig.getAddresses()) {
                config.getNetworkConfig().addAddress(address);
            }

            config.getConnectionStrategyConfig()
                  .setAsyncStart(true)
                  .setReconnectMode(ClientConnectionStrategyConfig.ReconnectMode.ASYNC);

            config.getNetworkConfig()
                  .setConnectionAttemptLimit(0) // infinite (Integer.MAX_VALUE) attempts to reconnect
                  .setConnectionTimeout(5000);

            client = HazelcastClient.newHazelcastClient(config);
        }
    }

    @Override
    public boolean isCacheEnabled() {
        ServersConfig.WidgetCache widgetCache = getWidgetCacheSettings();
        return widgetCache != null && widgetCache.getEnabled();
    }

    @Override
    public boolean isCacheAlive() {
        boolean aliveResult = false;
        if (isCacheEnabled() && client != null) {
            try {
                IMap<Object, Object> defaultMap = client.getMap("default");
                if (defaultMap != null) {
                    defaultMap.size(); // will throw Hazelcast exception if cluster is down
                    aliveResult = true;
                }
            } catch (Exception e) {
                log.error("Connection to hazelcast cluster is lost. Reason : {}", e.getMessage());
            }
        }
        return aliveResult;
    }
}

Answer 4

与isRunning() may be true even if cluster is down一样，我将采用以下方法（@konstantin-zyubin's answer和this的混合体）。不需要事件监听器，这对我的设置是一个优势：

if (!hazelcastInstance.getLifecycleService().isRunning()) {
  return Health.down().build();
}

int parameterCount;
LocalTopicStats topicStats;
try {
  parameterCount = hazelcastInstance.getMap("parameters").size();
  topicStats = hazelcastInstance.getTopic("myTopic").getLocalTopicStats();
} catch (Exception e) {
  // instance may run but cluster is down:
  Health.Builder builder = Health.down();
  builder.withDetail("Error", e.getMessage());
  return builder.build();
}

Health.Builder builder = Health.up();
builder.withDetail("parameterCount", parameterCount);
builder.withDetail("receivedMsgs", topicStats.getReceiveOperationCount());
builder.withDetail("publishedMsgs", topicStats.getPublishOperationCount());
return builder.build();

如何从java客户端检查hazelcast集群是否存活？

4 个答案: