Shared HTTP Servers not processing if response is not written into

Question

I have this code:

void handle(HttpRequest request) async {
  request.response.write('Hello');
  await Future.delayed(Duration(seconds: 5));
  request.response.close();
}

void main() {
  var server = await HttpServer.bind(InternetAddress.loopbackIPv4, 8080);
  server.listen(handle);
}

And that works properly, all the requests are processed in the same time, now I'm wondering why if I move the response.write after the Future, it can only processes only one request at time.

I can reproduce this only in Chromium browser, in Internet Explorer, Edge or CURL requests this doesn't happen.

void handle(HttpRequest request) async {
  print('Request on ${Isolate.current.hashCode}');
  await Future.delayed(Duration(seconds: 5));
  request.response.write('Hello');
  request.response.close();
}

Any info if there is a fix(leaving the response.write after the Future) or any explanation about why this is happening is welcome.

Answer 1

Modified your code like so:

void handle(HttpRequest request) async {
  print('A');
  await Future.delayed(Duration(seconds: 5));
  print('B');
  request.response.write('Hello');
  print('C');
  request.response.close();
}

2 tabs open in chrome, sending requests. One would expect to see A-A-B-C-B-C in console but in fact it's not so: A-B-C-A-B-C. @julemand101 pointed out, it has something to do with how Chrome handles connections/caches... Something under the hood. If you disable the cache in dev-tools, you get the result you expect. So it's unrelated to how Dart works and in fact a browser-related oddity.