Race condition in AtLookupImpl._process

[gkc]

Describe the bug

• AtLookupImpl._process() does a few things - authenticates if necessary, sends a command, reads a response
• The intent is that all of that should happen as a single atomic group
• However there is no mutex guaranteeing that. As a result, for example, a caller can receive the response from a different request.

To Reproduce

• Have one piece of code for atSign_1 which is in a loop which calls AtClient.put() twice in rapid succession with two different keys, key1 and key2, which are sharedWith atSign_2, then waits for a second before doing it again
• Have another piece of code for atSign_2 which has subscribed to notifications, and in the notification callback calls AtClient.get() for whichever key (key1 or key2)

Expected behaviour

• No race condition

Fixed by #139

[murali-shris]

import 'dart:io';

import 'package:at_client/at_client.dart'; import 'package:at_client/src/manager/at_client_manager.dart'; import 'package:at_utils/at_logger.dart';

import 'dart:convert'; import 'dart:typed_data'; import 'package:crypto/crypto.dart';

void main() async { AtSignLogger.root_level = 'finest'; final atSign = 'alice'; var atClientManager = await AtClientManager.getInstance() .setCurrentAtSign(atSign, 'wavi', _getPreference()); try { while (true) { print('sync in progress'); var a = await atClientManager.syncService.isInSync(); print('Are we waiting ?' + a.toString()); sleep(Duration(seconds: 5)); } } on Exception catch(e, trace) { print(e); print(trace); } print('OK Ready'); }

AtClientPreference _getPreference() { var preference = AtClientPreference(); preference.hiveStoragePath = '/home/murali/work/2020/hive/client'; preference.commitLogPath = '/home/murali/work/2020/hive/client/commit'; preference.isLocalStoreRequired = true; preference.privateKey = ''; preference.rootDomain = 'root.atsign.org'; var hashFile = _getShaForAtSign('@zathura97tall'); preference.keyStoreSecret = _getKeyStoreSecret( '/home/murali/work/2020/hive/client/' + hashFile + '.hash'); return preference;

}

List _getKeyStoreSecret(String filePath) { var hiveSecretString = File(filePath).readAsStringSync(); var secretAsUint8List = Uint8List.fromList(hiveSecretString.codeUnits); return secretAsUint8List; }

String _getShaForAtSign(String atsign) { var bytes = utf8.encode(atsign); return sha256.convert(bytes).toString(); }

[murali-shris]

@gkc above code doesn't complete successfully with trunk branch of at_client pointing to your branch of at_lookup quickFixAtLookupRaceCondition In _processSyncRequests() _syncInProgress = true; final serverCommitId = await _getServerCommitId();// stats:3 request probably is sent(unable to confirm since server has only INFO logs). The response is not received and _syncInProgress never gets set to false.

[murali-shris]

@gkc above code doesn't complete successfully with trunk branch of at_client pointing to your branch of at_lookup quickFixAtLookupRaceCondition In _processSyncRequests() _syncInProgress = true; final serverCommitId = await _getServerCommitId();// stats:3 request probably is sent(unable to confirm since server has only INFO logs). The response is not received and _syncInProgress never gets set to false.

@gkc after running the tests multiple times I figured that issue happens even without your code changes..Issue requires a fix in SyncServiceImpl.

[gkc]

Yep it's unrelated

[gkc]

Closing - fixed by #139 and new at_lookup package 3.0.8 published