Reproducer.java

public class Reproducer {
  
    HttpServer server = vertx.createHttpServer();
    server.requestHandler(req -> {
      req.setExpectMultipart(true);
      req.endHandler(v -> {
        System.out.println(req.formAttributes().size());
        req.response().end();
      });
    });
    server.listen(8080, "localhost").toCompletionStage().toCompletableFuture().get();

    HttpClient client = vertx.createHttpClient();

    client.request(new RequestOptions()
      .setMethod(HttpMethod.POST)
      .setHost("localhost")
      .setPort(8080)).onComplete(onSuccess(req -> {
      req.setChunked(true);
      req.putHeader("content-type", "application/x-www-form-urlencoded");
      req.write("framework=vertx");
      send(req, 32_000_000
      );
      req
        .response()
        .compose(resp -> resp.body())
        .onComplete(onSuccess(v -> testComplete()));
    }));

    vertx.setPeriodic(1000, id -> {
      System.out.println(Runtime.getRuntime().freeMemory());
    });

    await();
  }

  private int seq = 0;
  private Buffer buffer = Buffer.buffer(TestUtils.randomAlphaString(2048));

  private void send(HttpClientRequest req, int amount) {
    int num = Math.min(64, amount);
    for (int i = 0;i < num;i++) {
      req.write("&item-" + seq++ + "=");
      req.write(buffer);
    }
    int remaining = amount - num;
    if (req.writeQueueFull()) {
      req.drainHandler(v -> {
        send(req, remaining);
      });
      return;
    }
    if (remaining == 0) {
      req.end();
    } else {
      vertx.runOnContext(v -> send(req, remaining));
    }
  }

}