Question about restore connection

[VladimirLuzhin]

grpc_dart: 1.0.2

Hello! My team decided to try gRPS in our new project, but we had a question about how to properly restore the connection in the following situation: 1) There was a short-term loss of communication with the server (for example, the Wi-Fi router was restarted) 2) There has been a long loss of communication with the server 3) The server has become unavailable

Now we have written a test application, a server in C # and, as a client, a mobile application on flutter. When we reproduced the situations described above, we received the following error codes: 2, 4, 14. Client code:

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:grpc/grpc.dart' as grpc;
import 'package:grpc/service_api.dart';
import 'package:grpc_test/gen/lib/hello.pbgrpc.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'gRPC test',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'gRPC test page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TestServiceClient _client;
  String _counter = "";

  var _controller;
  Stream<RpcRequest> _stream;

  ResponseStream<RpcResponse> _responseStream;

  ClientChannel _channel;

  _MyHomePageState() {
    _channel = ClientChannel(
        "10.10.230.110",
        port: 50051,
        options: grpc.ChannelOptions(
            credentials: grpc.ChannelCredentials.insecure(),
            idleTimeout: Duration(seconds: 5),
            backoffStrategy: (_) => Duration(seconds: 5)
        ));

    _client = TestServiceClient(_channel);
    _controller = StreamController<RpcRequest>.broadcast();
    _stream = _controller.stream;
    _stream.listen((data) {
      print("Stream data $data");
    },
        onError: (error) {
          print("Stream error ${error.toString()}");
        },
        onDone: () {
          print("Stream done}");
        }
    );
    _controller.onCancel = () {
      print("Controller onCancel");
    };

    createCall();
  }

  void _incrementCounter() {
    setState(() {
      _counter = "Started";
    });
  }

  @override
  void dispose() {
    _controller.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(

        title: Text(widget.title),
      ),
      body: Center(

        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextField(
              onSubmitted: (text) {
                _controller.add(RpcRequest()..info = text..id = "qwerty");
              },
            ),
            Text(
              'Messages from server',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }

  Future<void> createCall() async {
    final currentState = (await _channel.getConnection()).state;
    print("State ${currentState.toString()}");

    final meta = new Map<String, String>();
    meta.addEntries([new MapEntry<String, String>("id", "mobileId")]);
    _responseStream = _client.sendReuqest(_stream, options: CallOptions(metadata: meta));
    _responseStream.listen((RpcResponse response) {
      print("${response.response}");
      setState(() {
        _counter = "${response.response}";
      });
    },
      onError: (error) {
        print("${error.toString()}");
        if (error is grpc.GrpcError) {
          setState(() {
            _counter = error.toString();
          });
          if (error.code == 2 || error.code == 4 || error.code == 14) {
            Future.delayed(Duration(seconds: 1), () => createCall());
          }
        }
      },
      onDone: () {
        print("connection done");
      }
    );
  }
}

And actually the question itself, we have to completely re-create the connection with such errors? Or should it recover itself? Thanks in advance for your reply.

[quetool]

I would like to know this as well

[lucaslcode]

@VladimirLuzhin This was possibly fixed in #231, is the issue still present?

[zs-dima]

is the issue still present?

Yes

[mraleph]

We believe that connection handling is now more robust. If it is not (e.g. you have examples where client does not gracefully reconnect and reissue requests) please report separate issues. Thanks.