// In the application initialization setup a registry
Registry registry = new DefaultRegistry();
Server s = new Server(registry);

public class Server {
  private final Registry registry;
  private final Id requestCountId;
  private final Timer requestLatency;
  private final DistributionSummary responseSizes;

  @Inject
  public Server(Registry registry) {
    this.registry = registry;

    // Create a base id for the request count. The id will get refined with
    // additional dimensions when we receive a request.
    requestCountId = registry.createId("server.requestCount");

    // Create a timer for tracking the latency. The reference can be held onto
    // to avoid additional lookup cost in critical paths.
    requestLatency = registry.timer("server.requestLatency");

    // Create a distribution summary meter for tracking the response sizes.
    responseSizes = registry.distributionSummary("server.responseSizes");

    // Gauge type that can be sampled. In this case it will invoke the
    // specified method via reflection to get the value. The registry will
    // keep a weak reference to the object passed in so that registration will
    // not prevent garbage collection of the server object.
    registry.methodValue("server.numConnections", this, "getNumConnections");
  }

  public Response handle(Request req) {
    final long s = System.nanoTime();
    requestLatency.record(() -> {
      try {
        Response res = doSomething(req);

        // Update the counter id with dimensions based on the request. The
        // counter will then be looked up in the registry which should be
        // fairly cheap, such as lookup of id object in a ConcurrentHashMap.
        // However, it is more expensive than having a local variable set
        // to the counter.
        final Id cntId = requestCountId
          .withTag("country", req.country())
          .withTag("status", res.status());
        registry.counter(cntId).increment();

        responseSizes.record(res.body().size());

        return res;
      } catch (Exception e) {
        final Id cntId = requestCountId
          .withTag("country", req.country())
          .withTag("status", "exception")
          .withTag("error", e.getClass().getSimpleName());
        registry.counter(cntId).increment();
        throw e;
      }
    });
  }

  public int getNumConnections() {
    // however we determine the current number of connections on the server
  }
}