Add delay on node transfer to hopefully prevent 4006 (#24)

* Fix transfer delay, double delay to 1000ms

* Add closecode reconnect example

---------

Co-authored-by: Freya Arbjerg <[email protected]>

Author: duncte123

src/main/kotlin/dev/arbjerg/lavalink/client/LavalinkClient.kt

@@ -11,6 +11,7 @@ import reactor.core.publisher.Flux
 import reactor.core.publisher.Sinks
 import java.io.Closeable
 import java.net.URI
+import java.time.Duration
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.CopyOnWriteArrayList
 import java.util.concurrent.Executors
@@ -203,7 +204,8 @@ class LavalinkClient(val userId: Long) : Closeable, Disposable {
                 val voiceRegion = link.cachedPlayer?.voiceRegion
 
                 link.state = LinkState.CONNECTING
-                link.transferNode(loadBalancer.selectNode(region = voiceRegion))
+                // The delay is used to prevent a race condition in Discord, causing close code 4006
+                link.transferNode(loadBalancer.selectNode(region = voiceRegion), delay = Duration.ofMillis(1000))
             }
         }
     }

src/main/kotlin/dev/arbjerg/lavalink/client/Link.kt

@@ -61,15 +61,14 @@ class Link(
      */
     fun loadItem(identifier: String) = node.loadItem(identifier)
 
-    internal fun transferNode(newNode: LavalinkNode) {
+    internal fun transferNode(newNode: LavalinkNode, delay: Duration = Duration.ZERO) {
         val player = node.getCachedPlayer(guildId)
 
         if (player != null) {
             node.removeCachedPlayer(guildId)
             newNode.createOrUpdatePlayer(guildId)
                 .applyBuilder(player.stateToBuilder())
-                // Delay by 500ms to hopefully prevent a race-condition from triggering
-                .delayElement(Duration.ofMillis(500))
+                .delaySubscription(delay)
                 .subscribe()
         }
 

testbot/src/main/java/me/duncte123/testbot/Main.java

@@ -5,6 +5,7 @@
 import dev.arbjerg.lavalink.client.loadbalancing.builtin.VoiceRegionPenaltyProvider;
 import dev.arbjerg.lavalink.libraries.jda.JDAVoiceUpdateListener;
 import net.dv8tion.jda.api.JDABuilder;
+import net.dv8tion.jda.api.entities.channel.unions.AudioChannelUnion;
 import net.dv8tion.jda.api.requests.GatewayIntent;
 import net.dv8tion.jda.api.utils.cache.CacheFlag;
 import org.slf4j.Logger;
@@ -16,6 +17,8 @@
 public class Main {
     private static final Logger LOG = LoggerFactory.getLogger(Main.class);
 
+    private static final int SESSION_INVALID = 4006;
+
     public static void main(String[] args) throws InterruptedException {
         final var token = System.getenv("BOT_TOKEN");
         final LavalinkClient client = new LavalinkClient(Helpers.getUserIdFromToken(token));
@@ -25,15 +28,35 @@ public static void main(String[] args) throws InterruptedException {
         registerLavalinkListeners(client);
         registerLavalinkNodes(client);
 
-        JDABuilder.createDefault(token)
+        final var jda = JDABuilder.createDefault(token)
             .setVoiceDispatchInterceptor(new JDAVoiceUpdateListener(client))
             .enableIntents(GatewayIntent.GUILD_VOICE_STATES)
             .enableCache(CacheFlag.VOICE_STATE)
             .addEventListeners(new JDAListener(client))
             .build()
             .awaitReady();
-    }
 
+        // Got a lot of 4006 closecodes? Try this "fix"
+        client.on(WebSocketClosedEvent.class).subscribe((event) -> {
+            if (event.getCode() == SESSION_INVALID) {
+                final var guildId = event.getGuildId();
+                final var guild = jda.getGuildById(guildId);
+
+                if (guild == null) {
+                    return;
+                }
+
+                final var connectedChannel = guild.getSelfMember().getVoiceState().getChannel();
+
+                // somehow
+                if (connectedChannel == null) {
+                    return;
+                }
+
+                jda.getDirectAudioController().reconnect(connectedChannel);
+            }
+        });
+    }
 
 
     private static void registerLavalinkNodes(LavalinkClient client) {