CloseableHttpAsyncClient client = HttpAsyncClients
        .custom()
        .setMaxConnTotal(1000)
        .setMaxConnPerRoute(1000)
        .build();

client.start();

ArrayList<Future<HttpResponse>> futures = new ArrayList<>();
ArrayList<HttpPost> requests = new ArrayList<>();

/* ... I build 100k requests ... */

for(HttpPost request : requests) {
  futures.add(client.execute(request, null));
}

/* ... record start time ... */

for(Future future : futures) {
  future.get();
}

/* ... print change since start time ... */