Firestore access broken after an offline attempt

Question

I'm trying to access to a Cloud Firestore with this piece of code :

void _submit(BuildContext context) async {
    final DocumentReference postRef = Firestore.instance.document(dbPath);
    Firestore.instance.runTransaction((transaction) async {
        DocumentSnapshot freshSnap = await transaction.get(postRef);
        await transaction.update(freshSnap.reference, {
            'value': freshSnap['value'] + 1
        });
   });
}

If wifi or mobile data are on, everything works fine. (as expected)

If wifi and mobile data are off, it does not work. (as expected). But when I wait until the timeout (after calling the method) and only then, turn mobile data and wifi on, it does not work anymore and I get the following errors :

E/flutter ( 7041): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter ( 7041): PlatformException(Error performing transaction, Timed out waiting for Task, null)
E/flutter ( 7041): #0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:547:7)
E/flutter ( 7041): #1      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:279:18)
E/flutter ( 7041): <asynchronous suspension>
E/flutter ( 7041): #2      Firestore.runTransaction (file:///C:/{myPath}/flutter/.pub-cache/hosted/pub.dartlang.org/cloud_firestore-0.7.3/lib/src/firestore.dart:115:10)
E/flutter ( 7041): <asynchronous suspension>
E/flutter ( 7041): #3      _FeedbackPageState._submitFeedback (package:appli_salon_data/view/program/FeedbackPage.dart:74:26)
E/flutter ( 7041): <asynchronous suspension>
E/flutter ( 7041): #4      _FeedbackPageState.build.<anonymous closure> (package:appli_salon_data/view/program/FeedbackPage.dart:60:26)
E/flutter ( 7041): #5      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:494:14)
E/flutter ( 7041): #6      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:549:30)
E/flutter ( 7041): #7      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
E/flutter ( 7041): #8      TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:161:9)
E/flutter ( 7041): #9      TapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:123:7)
E/flutter ( 7041): #10     GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:156:27)
E/flutter ( 7041): #11     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:147:20)
E/flutter ( 7041): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:121:22)
E/flutter ( 7041): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:101:7)
E/flutter ( 7041): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:64:7)
E/flutter ( 7041): #15     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:48:7)
E/flutter ( 7041): #16     _invoke1 (dart:ui/hooks.dart:134:13)
E/flutter ( 7041): #17     _dispatchPointerDataPacket (dart:ui/hooks.dart:91:5)

(not expected)

The method won't work again until I relaunch the app.

If anyone has some explanation about this behaviour, feel free to answer :)

UPDATE : I tried this :

1. Switch off Wifi
2. Try to run the transaction - results in expected failure
3. Switch on Wifi
4. Try to run the transaction

Here is the interesting part : at step 4, the transaction is "immediately" run twice, both times getting the error :

PlatformException(Error performing Transaction#get, UNAVAILABLE: Unable to resolve host firestore.googleapis.com, null)

when calling transaction.get(postRef).

Could it mean that Firestore somehow loses all access to the host after losing Internet connection briefly once ? How can I fix that ?

Answer 1

Have you tried enabling local persistence? Not sure if that'll catch the issue, but it might be worth a try. I believe this is done using the persistenceEnabled parameter in the settings method:

Firestore.instance.settings(persistenceEnabled: true)

Keep in mind that this should only be done once, so it should go somewhere in your code that won't get called every time you access any Firestore data.