SecureSocket handshake can stall the main thread for long time

[besthyhy]

In my application, the SDK used before was 1.9 and everything worked fine. After upgrading to 1.12, android still works well, but ios will get stuck on the splash screen.

Detailed questions:

1. Sometimes the first time you start it will get stuck on the splash screen.
2. Manually kill the process and then enter the app, there is a high possibility that it will get stuck on the splash screen page.

Code situation

1. pubspec.yaml
   http: 0.12.0+4
2. lib/SplashPage.dart

class SplashPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _StdPageState();
  }
}

class _StdPageState extends State<SplashPage> {
  @override
  void initState() {
    super.initState();
    
    // send Http here
  }
}

3. lib/util/HttpsUtils.dart

import 'dart:convert' show utf8;
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:inlan_flutter/Config.dart';
import 'package:inlan_flutter/util/DataUtils.dart';
import 'package:inlan_flutter/util/I18nUtils.dart';
import 'package:inlan_flutter/util/JsonUtils.dart';
import 'package:inlan_flutter/util/LogUtils.dart';
import 'package:inlan_flutter/util/ToastUtils.dart';
import 'package:inlan_flutter/util/UpgradeUtils.dart';
import 'package:inlan_flutter/util/UuidUtils.dart';

class HttpsUtils {
  static void apiPostWithUrl(
      String url,
      Map<String, dynamic> body,
      BuildContext context,
      StackTrace callPositionStackTrace,
      State state,
      callback(json)) async {
    body["version"] = Config.apiVersion;
    body["httpId"] = UuidUtils.v4();
    body["lang"] = I18nUtils.languageCode();
    body["path"] = url;

    String fullUrl = Config.apiUrl + url;

    final apiClient = http.Client();

    try {
      await apiClient
          .post(fullUrl,
              headers: {"Content-Type": "application/json"},
              body: JsonUtils.encode(body))
          .then((response) {
        LogUtils.log(response.statusCode, StackTrace.current,
            tag: "statusCode");

        LogUtils.devLog(Config.apiUrl + url, callPositionStackTrace,
            tag: "apiUrl " + url);

        LogUtils.devLog(JsonUtils.prettyJson(body), callPositionStackTrace,
            tag: "req");

        LogUtils.devLog(
            JsonUtils.prettyStr(response.body), callPositionStackTrace,
            tag: "resp ${response.statusCode}");

        switch (response.statusCode) {
          case 200:
            callback(JsonUtils.parse(response.body));
            break;
          case 400:
            Map<String, dynamic> jsonObj = JsonUtils.parse(response.body);
            state.setState(() {
              ToastUtils.short(jsonObj["message"]);
            });
            break;
          case 401:
            Map<String, dynamic> jsonObj = JsonUtils.parse(response.body);
            state.setState(() {
              ToastUtils.withCallback(jsonObj["message"], () {
                DataUtils.setByService('login_data', '-1');
                DataUtils.setByService('isLogined', '-1');
                Navigator.pushNamedAndRemoveUntil(
                    context, '/account', (Route<dynamic> route) => false);
              });
            });
            break;
          case 403:
            break;
          case 406:
            UpgradeUtils().doForceUpgrade(context);
            break;
          case 422:
            Map<String, dynamic> jsonObj = JsonUtils.parse(response.body);
            state.setState(() {
              ToastUtils.short(jsonObj["message"]);
            });
            break;
        }
      });
    } finally {
      apiClient.close();
    }
  }
}

My temporary solution

  void initState() {
    super.initState();
    Timer timer = new Timer(new Duration(milliseconds: 1200), () {
      // send Http here
    });
    
  }

Expected solution

1. What causes the freeze?
2. A better solution?

[tp]

@besthyhy

We ran into the same issue. For us our the issue was caused by our "User-Agent overwrite" not working anymore with Flutter 1.12, which cause the server to respond with status 400.

Maybe providing some user-agent header (headers: {"User-Agent": "foo"}), would also fix your issue and obliviate the need for the timeout?

[ghostgzt]

me too!
It is due to some https url!

[beiger]

url: https://gank.io/api/v2/categories/Article
method: GET
my location: China

ios ui freeze on http request

[lanistor]

Same issue. It's really a very very very terrible problem.
My environment:
http: v0.12.0+2 ~ 4
Dart: 2.8.0
Flutter: 1.15.3

Relative issues: dart-lang/http#400.

[natebosch]

Does this replicate when you use dart:io directly to make the request?

The comments so far don't give much to investigate - is this because there is a Future that does not resolve?

Does anyone have a minimal reproduction?

[lanistor]

@natebosch In my case, i was using dart:io and package:http/http.dart at the same time in my one dart file, dart:io is used to add platform info to http headers.
After readed your words, i removed import dart:io line, it worked fine suddenly, and then i added import dart:io back, it works fine too, and the error cannot occour ever, even i run flutter clean to clean my build folder and run again. It' really wired.
Now i removed import dart:io just in case. But i really don't know why.

[beiger]

If the website uses lets encrypt certification, the ui will be freeze on https request.
iOS platform
url: https://letsencrypt.org/
method: GET
use dart:io directly

[natebosch]

@vifird - the concern isn't having imports to dart:io in the same file - it is whether the suspected bug is caused by this package, or by dart:io. When you use package:http on mobile with flutter it is acting as a thin wrapper around HttpClient. When you use this package on the web it is a thin wrapper around HttpRequest. Usually when something fundamentally doesn't work it can be reproduced without using this package at all, but by using dart:io or dart:html directly. We ask for reproduction cases using these imports to help us route the bug to the right place. We can't solve any problem in this repository if the bug isn't caused by this repository.

@beiger - Can you get more specific? Is there a Future that should complete but doesn't? Does the entire runtime crash?

use dart:io directly

If you can reproduce without using this package we will need to route the issue to the Dart SDK repo. Do you have a complete and minimal reproduction case?

[beiger]

@natebosch
This is my code:

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:package_info/package_info.dart';

class AboutPage extends StatefulWidget {
 @override
 AboutPageState createState() => AboutPageState();
}

class AboutPageState extends State<AboutPage> {
 String _version = "";
 double _top = -20;

 @override
 Widget build(BuildContext context) {
  return Scaffold(
   appBar: AppBar(
    title: "about",
   ),
   body: Stack(
    children: <Widget>[
     AnimatedPositioned(
      duration: const Duration(milliseconds: 2000),
      curve: Curves.bounceOut,
      left: 0,
      top: _top,
      child: Container(
       width: MediaQuery.of(context).size.width,
       child: Center(
        child: Text(
         _version,
         style: TextStyle(
          fontSize: 28,
          color: Colors.blue,
          fontWeight: FontWeight.bold
         ),
        ),
       ),
      ),
     )
    ],
   ),
  );
 }

 @override
 void initState() {
  super.initState();
  _getVersion();
  test();
 }

 Future<void> test() async {
//  var url="https://gank.io/";  // Letsencrypt CA
  var url='https://github.com/dart-lang/http/issues/374'; // other certificate
  var httpClient = HttpClient();
  var request = await httpClient.getUrl(Uri.parse(url));
  var response = await request.close();
  print(response);
 }

 void _getVersion() {
  Future.delayed(Duration(microseconds: 500), () {
   PackageInfo.fromPlatform().then((value) {
    setState(() {
     _version =value.version;
     _top = MediaQuery.of(context).size.height / 2.7;
    });
   });
  });
 }
}

Letsencrypt CA url:

When you open this page, sometimes the page gets stuck in the middle, sometimes the animation gets stuck.

Other CA url:
The animation on the page is very smooth.

[beiger]

Here is my iOS info:

There is no runtime crash.

[natebosch]

If the website uses lets encrypt certification, the ui will be freeze on https request.

Have you tried using an HttpClient from dart:io and setting the badCertificateCallback?

https://api.dart.dev/stable/2.7.2/dart-io/HttpClient/badCertificateCallback.html

[natebosch]

I think I'll move to the SDK repo for now. It's not entirely clear to me what the issue is, but I don't see any evidence it's related to package:http.

[beiger]

I'm using HttpClient from dart:io. I tried to set the badCertificateCallback, the program did not enter callback.

I've only had this kind of stuck situation since last month, and there are some people who have met earlier than me. It used to run well with the same code several month ago. This is only on IOS, Android is good.

[mraleph]

I don't think there is enough information here for us to diagnose problem.

HTTP processing is done asynchronously so it can't just block your UI thread.

I would start by looking for exceptions in the logs.