public class MetricHolder {
  private final AtomicReference<ConcurrentHashMap<String, AtomicLongMap<String>>> metricHolderByType =
      new AtomicReference<>(new ConcurrentHashMap<String, AtomicLongMap<String>>());
  private final ScheduledExecutorService executorService = Executors
      .newSingleThreadScheduledExecutor();

  private static class Holder {
    private static final MetricHolder INSTANCE = new MetricHolder();
  }

  public static MetricHolder getInstance() {
    return Holder.INSTANCE;
  }

  private MetricHolder() {
    executorService.scheduleAtFixedRate(new Runnable() {
      @Override
      public void run() {
        SendToDatabase.getInstance().send(
            metricHolderByType
                .getAndSet(new ConcurrentHashMap<String, AtomicLongMap<String>>()));
      }
    }, 0, 30, SECONDS);
  }

  // this is called from multiple threads
  public void incrementByType(String type, TypeOfMetrics... metricsType) {
    for (TypeOfMetrics metricType : metricsType) {
      ConcurrentMap<String, AtomicLongMap<String>> metricsHolderByType =
          metricHolderByType.get();
      AtomicLongMap<String> metricHolder = metricsHolderByType.get(type);
      if (metricHolder == null) {
        metricHolder = AtomicLongMap.create();
        AtomicLongMap<String> currentMetricHolder =
            metricsHolderByType.putIfAbsent(type, metricHolder);
        if (currentMetricHolder != null) {
          metricHolder = currentMetricHolder;
        }
      }
      metricHolder.incrementAndGet(metricType.value);
    }
  }

  // this contains more metrics but for example I have few here
  public enum TypeOfMetrics {
    RECORDS_DROPPED("records-dropped"), TOTAL_EVENTS("total-events"), ENCODE_ERROR(
        "encode-error");
    private final String value;

    private TypeOfMetrics(String value) {
      this.value = value;
    }

    public String value() {
      return value;
    }

    @Override
    public String toString() {
      return name() + "=" + value;
    }
  };
}

SlackApi api = new SlackApi("slack-hook-url");
// Send simple message
api.call(new SlackMessage("#test-webhook-java", "Mafagafo", "message"));

{"type":"whatever is the key for the map where RECORDS_DROPPED is greater than zero", "metric":"name of metric for eg: it can be records-dropped", "count":"whatever is the count which is greater than zero for records-dropped example"}