灶王经

書名： Dart：Scalable Application Development
作者名： Davy Mitchell Sergey Akopkokhyants Ivo Balbaert
本章字數： 209字
更新時間： 2021-07-09 18:56:24

Load testing revisited

The initial load testing application was rather limited, and though of use, it did not give a realistic picture with so many requests thrown at once at the server application without waiting for a response.

Updating the load tester

The new version of the load testing application will make a single HTTP call and await the result before calling the next. This takes place in the main.dart source file. Note that the main function itself in now marked as async. The await command is used in the calling loop of the main function, as follows:

main() async {
  print("Starting...");

  var url = "http://127.0.0.1:8080/index.html";
  var hc = new HttpClient();
  var watch = new Stopwatch();
  int attemptedRequests = 200;

  print("Starting testing...");
  watch.start();

  for (int i = 0; i < attemptedRequests; i++) {
    await callWebPage(hc, url, i, watch);
  }

  watch.stop();
  print("${watch.elapsed.inMilliseconds}");
}

The callWebPage method needs to be marked as async too, as await will be used twice:

callWebPage(HttpClient webClient, String targetURL, int requestNumber,
    Stopwatch watch) async {
  HttpClientRequest request;
  HttpClientResponse response;
  request = await webClient.getUrl(Uri.parse(targetURL));
  response = await request.close();
  print("$requestNumber, ${response.statusCode}, ${watch.elapsed.inMilliseconds}");
}

The two operations of unknown duration, the URL fetch and closing of the response, are waited upon before the output to the screen is processed.

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Dart：Scalable Application Development

Load testing revisited

Updating the load tester