why limit Metric cardinality ?

[Roiocam]

what am i doing

i am currently using OpenTelemetry record something metrics about akka. like mailbox size.

but actor model will create thousands of objects. my extension(instrumentation) will record them all.

what is the problem

everything is correcttly when running my dev laptop. but when i deploy to server and created more than 2000 actor, something happend.

It seems to be related to this pr: #3831

WARN io.opentelemetrv.sdk.metrics.internal.state.AsvnchronousMetricStorage Instrument mailbox_size has exceeded the maximum alloyed accumulations (2000)

how the code look likes

Metrics

public class MailboxMetrics {
    private static Meter meter = GlobalOpenTelemetry.getMeter("some name");
    private static Map<ActorPath, Long> mailboxSizeMap = new ConcurrentHashMap<>();

    @SuppressWarnings("unused")
    private static ObservableLongGauge mailboxSize =
            meter.gaugeBuilder("mailbox_size")
                    .setDescription("Mailbox Size")
                    .ofLongs()
                    .buildWithCallback(
                            c -> {
                                Set<ActorPath> allKey = mailboxSizeMap.keySet();
                                for (ActorPath key : allKey) {
                                    c.record(mailboxSizeMap.get(key), getAttributes(key));
                                }
                            });

    public static void registerActor(ActorPath path) {
        mailboxSizeMap.putIfAbsent(path, 0L);
    }

    public static void setActorMailboxSize(ActorPath path, int size) {
        mailboxSizeMap.putIfAbsent(path, Long.valueOf(size));
    }


    private static Attributes getAttributes(ActorPath path) {
        ArrayList<String> elements = new ArrayList<>();
        path.getElements().forEach(elements::add);
        String type =
              elements.stream()
                        .findFirst()
                        .orElse("system");
        String name = path.name();
        String pathStr = path.toStringWithoutAddress();
        return Attributes.builder()
                .put("type", type)
                .put("path", pathStr)
                .put("name", name)
                .build();
    }
}

Advice

public static class DequeueAdvice {

        @Advice.OnMethodEnter
        public static void onMessage(@Advice.This Object object) {
            if (!(object instanceof Mailbox)) {
                return;
            }
            Mailbox obj = (Mailbox) object;
            int size = obj.numberOfMessages();
            ActorRef self = obj.actor().getSelf();
            if (Objects.isNull(obj.actor()) || Objects.isNull(obj.actor().getSelf())) {
                return;
            }
            ActorPath path = self.path();
            MailboxMetrics.setActorMailboxSize(path, size);
        }
    }

question

Did I using this wrong code? what is the best practice for mesuring application code ?

why Metric cardinality limit is constant?

Thank you for taking the time to answer.

[Roiocam]

seem like i open this on the wrong repo.

i found same issue on: open-telemetry/opentelemetry-java#4647

i got the answer, this discussions should be ignore.