xmpp: Add support for setting reconnection policies

lib/service/service.dart

@@ -9,6 +9,7 @@ import "package:moxxyv2/xmpp/connection.dart";
 import "package:moxxyv2/xmpp/presence.dart";
 import "package:moxxyv2/xmpp/message.dart";
 import "package:moxxyv2/xmpp/ping.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0054.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0060.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0066.dart";
@@ -166,7 +167,7 @@ Future<void> entrypoint() async {
   // Init the UDPLogger
   await initUDPLogger();
 
-  final connection = XmppConnection();
+  final connection = XmppConnection(ExponentialBackoffReconnectionPolicy());
   connection.registerManagers([
       MoxxyStreamManagementManager(),
       MoxxyDiscoManager(),

lib/xmpp/connection.dart

@@ -1,5 +1,4 @@
 import "dart:async";
-import "dart:math";
 
 import "package:moxxyv2/xmpp/socket.dart";
 import "package:moxxyv2/xmpp/buffer.dart";
@@ -12,6 +11,7 @@ import "package:moxxyv2/xmpp/events.dart";
 import "package:moxxyv2/xmpp/iq.dart";
 import "package:moxxyv2/xmpp/presence.dart";
 import "package:moxxyv2/xmpp/roster.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/sasl/authenticator.dart";
 import "package:moxxyv2/xmpp/sasl/authenticators.dart";
 import "package:moxxyv2/xmpp/managers/base.dart";
@@ -30,6 +30,7 @@ import "package:uuid/uuid.dart";
 import "package:synchronized/synchronized.dart";
 import "package:logging/logging.dart";
 import "package:meta/meta.dart";
+import "package:moxlib/moxlib.dart";
 
 enum XmppConnectionState {
   notConnected,
@@ -94,6 +95,7 @@ class XmppConnection {
   XmppConnectionState _connectionState;
   late final Stream<String> _socketStream;
   late ConnectionSettings _connectionSettings;
+  final ReconnectionPolicy _reconnectionPolicy;
   
   /// Stream properties
   ///
@@ -112,8 +114,6 @@ class XmppConnection {
   RoutingState _routingState;
   /// The currently bound resource or "" if none has been bound yet.
   String _resource;
-  /// Counter for how manyy we have tried to reconnect.
-  int _currentBackoffAttempt;
   /// For indicating in a [ConnectionStateChangedEvent] that the event occured because we
   /// did a reconnection.
   bool _resuming;
@@ -122,9 +122,8 @@ class XmppConnection {
   bool _disconnecting;
   /// For indicating whether we expect a socket closure due to StartTLS.
   bool _performingStartTLS;
-  /// Timers for the keep-alive ping and the backoff connection process.
+  /// Timers for the keep-alive ping.
   Timer? _connectionPingTimer;
-  Timer? _backoffTimer;
   /// Completers for certain actions
   Completer<XmppConnectionResult>? _connectionCompleter;
 
@@ -137,16 +136,18 @@ class XmppConnection {
   /// [socket] is for debugging purposes.
   /// [connectionPingDuration] is the duration after which a ping will be sent to keep
   /// the connection open. Defaults to 15 minutes.
-  XmppConnection({
+  XmppConnection(
+    ReconnectionPolicy reconnectionPolicy,
+    {
       BaseSocketWrapper? socket,
       this.connectionPingDuration = const Duration(minutes: 5)
-  }) :
+    }
+  ) :
     _connectionState = XmppConnectionState.notConnected,
     _routingState = RoutingState.unauthenticated,
     _eventStreamController = StreamController.broadcast(),
     _resource = "",
     _streamBuffer = XmlStreamBuffer(),
-    _currentBackoffAttempt = 0,
     _resuming = true,
     _performingStartTLS = false,
     _disconnecting = false,
@@ -159,7 +160,11 @@ class XmppConnection {
     _incomingStanzaHandlers = List.empty(growable: true),
     _outgoingPreStanzaHandlers = List.empty(growable: true),
     _outgoingPostStanzaHandlers = List.empty(growable: true),
+    _reconnectionPolicy = reconnectionPolicy,
     _log = Logger("XmppConnection") {
+      // Allow the reconnection policy to perform reconnections by itself
+      _reconnectionPolicy.register(_attemptReconnection);
+
       _socketStream = _socket.getDataStream();
       // TODO: Handle on done
       _socketStream.transform(_streamBuffer).forEach(handleXmlStream);
@@ -295,15 +300,7 @@ class XmppConnection {
   void _attemptReconnection() {
     _setConnectionState(XmppConnectionState.notConnected);
     _socket.close();
-
-    if (_currentBackoffAttempt == 0) {
-      // TODO: This may to too long
-      final minutes = pow(2, _currentBackoffAttempt).toInt();
-      _currentBackoffAttempt++;
-      _backoffTimer = Timer(Duration(minutes: minutes), () {
     connect();
-      });
-    }
   }
   
   /// Called when a stream ending error has occurred
@@ -316,7 +313,7 @@ class XmppConnection {
     } 
 
     // TODO: This may be too harsh for every error
-    _attemptReconnection();
+    _reconnectionPolicy.onFailure();
   }
 
   /// Called whenever the socket creates an event
@@ -892,6 +889,11 @@ class XmppConnection {
   Future<void> _sendEvent(XmppEvent event) async {
     _log.finest("Event: ${event.toString()}");
 
+    // Specific event handling
+    if (event is AckRequestResponseTimeoutEvent) {
+      _reconnectionPolicy.onFailure();
+    }
+    
     for (var manager in _xmppManagers.values) {
       await manager.onXmppEvent(event);
     }
@@ -967,10 +969,7 @@ class XmppConnection {
       _resource = lastResource;
     }
 
-    if (_backoffTimer != null) {
+    _reconnectionPolicy.reset();
-      _backoffTimer!.cancel();
-      _backoffTimer = null;
-    }
 
     _resuming = true;
     await _sendEvent(ConnectingEvent());
@@ -993,7 +992,7 @@ class XmppConnection {
     if (!result) {
       handleError(null);
     } else {
-      _currentBackoffAttempt = 0;
+      _reconnectionPolicy.onSuccess();
       _log.fine("Preparing the internal state for a connection attempt");
       _performingStartTLS = false;
       _setConnectionState(XmppConnectionState.connecting);

lib/xmpp/reconnect.dart

@@ -0,0 +1,87 @@
+import "dart:async";
+import "dart:math";
+
+import "package:logging/logging.dart";
+import "package:meta/meta.dart";
+
+abstract class ReconnectionPolicy {
+  /// Function provided by [XmppConnection] that allows the policy
+  /// to perform a reconnection.
+  void Function()? performReconnect;
+
+  /// Called by [XmppConnection] to register the policy.
+  void register(void Function() performReconnect) {
+    this.performReconnect = performReconnect;
+
+    reset();
+  }
+  
+  /// In case the policy depends on some internal state, this state must be reset
+  /// to an initial state when [reset] is called. In case timers run, they must be
+  /// terminated.
+  void reset();
+
+  /// Called by the [XmppConnection] when the reconnection failed.
+  void onFailure();
+
+  /// Caled by the [XmppConnection] when the reconnection was successful.
+  void onSuccess();
+}
+
+/// A simple reconnection strategy: Make the reconnection delays exponentially longer
+/// for every failed attempt.
+class ExponentialBackoffReconnectionPolicy extends ReconnectionPolicy {
+  int _counter;
+  Timer? _timer;
+  Logger _log;
+
+  ExponentialBackoffReconnectionPolicy()
+  : _counter = 0,
+    _log = Logger("ExponentialBackoffReconnectionPolicy");
+
+  /// Called when the backoff expired
+  void _onTimerElapsed() {
+    performReconnect!();
+  }
+  
+  @override
+  void reset() {
+    _log.finest("Resetting internal state");
+    _counter = 0;
+
+    if (_timer != null) {
+      _timer!.cancel();
+      _timer = null;
+    }
+  }
+
+  @override
+  void onFailure() {
+    _log.finest("Failure occured. Starting exponential backoff");
+    _counter++;
+
+    if (_timer != null) {
+      _timer!.cancel();
+    }
+
+    _timer = Timer(Duration(seconds: pow(2, _counter).toInt()), _onTimerElapsed);
+  }
+
+  @override
+  void onSuccess() {
+    reset();
+  }
+}
+
+/// A stub reconnection policy for tests
+@visibleForTesting
+class TestingReconnectionPolicy extends ReconnectionPolicy {
+  @override
+  void onSuccess() {}
+
+  @override
+  void onFailure() {}
+
+  @override
+  void reset() {}
+}

test/xeps/xep_0198_test.dart

@@ -4,6 +4,7 @@ import "package:moxxyv2/xmpp/stanza.dart";
 import "package:moxxyv2/xmpp/settings.dart";
 import "package:moxxyv2/xmpp/jid.dart";
 import "package:moxxyv2/xmpp/connection.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/managers/attributes.dart";
 import "package:moxxyv2/xmpp/managers/data.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0198/xep_0198.dart";
@@ -45,7 +46,7 @@ XmppManagerAttributes mkAttributes(void Function(Stanza) callback) {
     isFeatureSupported: (_) => false,
     getFullJID: () => JID.fromString("hallo@example.server/uwu"),
     getSocket: () => StubTCPSocket(play: []),
-    getConnection: () => XmppConnection()
+    getConnection: () => XmppConnection(TestingReconnectionPolicy())
   );
 }
 

test/xeps/xep_0280_test.dart

@@ -2,6 +2,7 @@ import "package:moxxyv2/xmpp/connection.dart";
 import "package:moxxyv2/xmpp/jid.dart";
 import "package:moxxyv2/xmpp/settings.dart";
 import "package:moxxyv2/xmpp/stringxml.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/managers/attributes.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0280.dart";
 
@@ -31,7 +32,7 @@ void main() {
         isFeatureSupported: (_) => false,
         getFullJID: () => JID.fromString("bob@xmpp.example/uwu"),
         getSocket: () => StubTCPSocket(play: []),
-        getConnection: () => XmppConnection()
+        getConnection: () => XmppConnection(TestingReconnectionPolicy())
       );
       final manager = CarbonsManager();
       manager.register(attributes);

test/xeps/xep_0352_test.dart

@@ -3,6 +3,7 @@ import "package:moxxyv2/xmpp/settings.dart";
 import "package:moxxyv2/xmpp/namespaces.dart";
 import "package:moxxyv2/xmpp/stringxml.dart";
 import "package:moxxyv2/xmpp/jid.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/managers/attributes.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0352.dart";
 
@@ -33,7 +34,7 @@ void main() {
               isFeatureSupported: (_) => false,
               getFullJID: () => JID.fromString("some.user@example.server/aaaaa"),
               getSocket: () => StubTCPSocket(play: []),
-              getConnection: () => XmppConnection()
+              getConnection: () => XmppConnection(TestingReconnectionPolicy())
             )
           );
 
@@ -62,7 +63,7 @@ void main() {
               isFeatureSupported: (_) => false,
               getFullJID: () => JID.fromString("some.user@example.server/aaaaa"),
               getSocket: () => StubTCPSocket(play: []),
-              getConnection: () => XmppConnection()
+              getConnection: () => XmppConnection(TestingReconnectionPolicy())
           ));
 
           csi.setActive();

test/xmpp_test.dart

@@ -8,6 +8,7 @@ import "package:moxxyv2/xmpp/stanza.dart";
 import "package:moxxyv2/xmpp/presence.dart";
 import "package:moxxyv2/xmpp/roster.dart";
 import "package:moxxyv2/xmpp/events.dart";
+import "package:moxxyv2/xmpp/reconnect.dart";
 import "package:moxxyv2/xmpp/managers/attributes.dart";
 import "package:moxxyv2/xmpp/managers/data.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0030/xep_0030.dart";
@@ -39,7 +40,7 @@ Future<bool> testRosterManager(String bareJid, String resource, String stanzaStr
       isFeatureSupported: (_) => false,
       getFullJID: () => JID.fromString("$bareJid/$resource"),
       getSocket: () => StubTCPSocket(play: []),
-      getConnection: () => XmppConnection()
+      getConnection: () => XmppConnection(TestingReconnectionPolicy())
   ));
 
   final stanza = Stanza.fromXMLNode(XMLNode.fromString(stanzaString));
@@ -215,7 +216,7 @@ void main() {
         ]
       );
       // TODO: This test is broken since we query the server and enable carbons
-      final XmppConnection conn = XmppConnection(socket: fakeSocket);
+      final XmppConnection conn = XmppConnection(TestingReconnectionPolicy(), socket: fakeSocket);
       conn.setConnectionSettings(ConnectionSettings(
           jid: JID.fromString("polynomdivision@test.server"),
           password: "aaaa",
@@ -294,7 +295,7 @@ void main() {
         ]
       );
       bool receivedEvent = false;
-      final XmppConnection conn = XmppConnection(socket: fakeSocket);
+      final XmppConnection conn = XmppConnection(TestingReconnectionPolicy(), socket: fakeSocket);
       conn.setConnectionSettings(ConnectionSettings(
           jid: JID.fromString("polynomdivision@test.server"),
           password: "aaaa",
@@ -378,7 +379,7 @@ void main() {
         ]
       );
       bool receivedEvent = false;
-      final XmppConnection conn = XmppConnection(socket: fakeSocket);
+      final XmppConnection conn = XmppConnection(TestingReconnectionPolicy(), socket: fakeSocket);
       conn.setConnectionSettings(ConnectionSettings(
           jid: JID.fromString("polynomdivision@test.server"),
           password: "aaaa",
@@ -466,7 +467,7 @@ void main() {
           )
         ]
       );
-      final XmppConnection conn = XmppConnection(socket: fakeSocket);
+      final XmppConnection conn = XmppConnection(TestingReconnectionPolicy(), socket: fakeSocket);
       conn.setConnectionSettings(ConnectionSettings(
           jid: JID.fromString("polynomdivision@test.server"),
           password: "aaaa",
@@ -505,7 +506,7 @@ void main() {
               isFeatureSupported: (_) => false,
               getFullJID: () => JID.fromString("some.user@example.server/aaaaa"),
               getSocket: () => StubTCPSocket(play: []),
-              getConnection: () => XmppConnection()
+              getConnection: () => XmppConnection(TestingReconnectionPolicy())
           ));
 
           // NOTE: Based on https://gultsch.de/gajim_roster_push_and_message_interception.html