Higher memory usage, blocked thread when using vertx circuit breaker

Question

Context

I am getting high memory usage with the vertx circuit breaker. I am just using httpbin.org to get all success responses. For individual requests, it works fine. While running a load test the JVM old gen utilization is spiking up.

Reproducer

I have the main verticle code, pasting it here itself:

public class CleanServer extends AbstractVerticle {
Logger logger = Logger.getLogger(CleanServer.class.getName());

  @Override
  public void start(Promise<Void> startPromise) throws Exception {
      Router router = Router.router(vertx);
      CircuitBreakerCache cbc = new CircuitBreakerCache(vertx);
      router.route(HttpMethod.GET, "/get").handler(context -> {
          List<String> domains = context.queryParam("user");
          String domain = domains.get(0);
          CircuitBreaker cb = cbc.getCircuitBreaker(domain + context.request().path());
          HttpServerResponse serverResponse =
                  context.response().setChunked(true);
          cb.executeWithFallback(promise -> {
              WebClientOptions options = new WebClientOptions().setTryUseCompression(true).setTcpNoDelay(true).setTcpCork(true).setReceiveBufferSize(128).setConnectTimeout(400);
              WebClient client = WebClient.create(vertx, options);
              client.get(80, "httpbin.org", "/status/200")
                      .timeout(2000)
                      .send(ar -> {
                          if (ar.succeeded()) {
                              HttpResponse<Buffer> response = ar.result();
                              int statusCode = response.statusCode();
                              if (statusCode != 200) {
                                  promise.fail(response.statusMessage());
                              } else {
                                  serverResponse.end("Hello!!");
                                  promise.complete();
                              }
                          } else {
                              promise.fail(ar.cause().getMessage());
                          }
                      });
          }, v -> {
              // Executed when the circuit is opened
              logger.log(Level.INFO, domain + " Failed " + cb.state().toString() + " Error: Circuit open");
              serverResponse.setStatusCode(200).setStatusMessage("Circuit Open").end("Circuit Open");
              return context;
          });
      });

      // Create the HTTP server
      vertx.createHttpServer(new HttpServerOptions().setMaxInitialLineLength(10000))
              // Handle every request using the router
              .requestHandler(router)
              // Start listening
              .listen(8080)
              // Print the port
              .onSuccess(server ->
                      System.out.println(
                              "HTTP server started on port " + server.actualPort()
                      )
              );


  }
}

Circuit breaker options:

CircuitBreakerOptions() 
.setMaxFailures(50) 
.setTimeout(5000) 
.setFallbackOnFailure(true) 
.setResetTimeout(10000)));

Steps to reproduce

API used: http://localhost:8080/get?user=abc

When I hit the above API at 50 QPS for 30 minutes. The java heap is getting filled up.

Extra

<vertx.version>4.2.6</vertx.version>

JVM params used:

-XX:+UseG1GC -Xms4g -Xmx4g -XX:InitiatingHeapOccupancyPercent=70 -XX:MaxGCPauseMillis=200 -XX:ParallelGCThreads=20 -XX:ConcGCThreads=5

JVM memory with the load test.

Error:

WARNING: Thread Thread[vert.x-eventloop-thread-3,5,main] has been blocked for 3050 ms, time limit is 2000 ms

I think I am blocking the thread somewhere but not sure where exactly as the code seems pretty simple as given in the documentation.