Update for master changes and comments

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/VelocityServerConnection.java

@@ -50,6 +50,7 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
   private BackendConnectionPhase connectionPhase = BackendConnectionPhases.UNKNOWN;
   private long lastPingId;
   private long lastPingSent;
+  private boolean hasCompletedJoin = false;
 
   public VelocityServerConnection(VelocityRegisteredServer registeredServer,
       ConnectedPlayer proxyPlayer, VelocityServer server) {
@@ -204,6 +205,8 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
   }
 
   public void completeJoin() {
+    if (!hasCompletedJoin) {
+      hasCompletedJoin = true;
       if (connectionPhase == BackendConnectionPhases.UNKNOWN) {
         // Now we know
         connectionPhase = BackendConnectionPhases.VANILLA;
@@ -212,6 +215,7 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
         }
       }
     }
+  }
 
   boolean isGracefulDisconnect() {
     return gracefulDisconnect;
@@ -264,4 +268,15 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
   public void setConnectionPhase(BackendConnectionPhase connectionPhase) {
     this.connectionPhase = connectionPhase;
   }
+
+  /**
+   * Gets whether the {@link com.velocitypowered.proxy.protocol.packet.JoinGame}
+   * packet has been sent by this server.
+   *
+   * @return Whether the join has been completed.
+   */
+  public boolean hasCompletedJoin() {
+    return hasCompletedJoin;
+  }
+
 }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -46,10 +46,10 @@ import java.net.InetSocketAddress;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
-import java.util.Random;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
+import java.util.concurrent.ThreadLocalRandom;
 import net.kyori.text.Component;
 import net.kyori.text.TextComponent;
 import net.kyori.text.TranslatableComponent;
@@ -67,7 +67,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
       c -> "", TranslatableComponent::key);
   static final PermissionProvider DEFAULT_PERMISSIONS = s -> PermissionFunction.ALWAYS_UNDEFINED;
 
-  private static final ThreadLocal<Random> threadLocalRandom = ThreadLocal.withInitial(Random::new);
+  private static final ThreadLocalRandom threadLocalRandom = ThreadLocalRandom.current();
   private static final Logger logger = LogManager.getLogger(ConnectedPlayer.class);
 
   private final MinecraftConnection connection;
@@ -479,7 +479,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
   public void sendKeepAlive() {
     if (connection.getState() == StateRegistry.PLAY) {
       KeepAlive keepAlive = new KeepAlive();
-      keepAlive.setRandomId(threadLocalRandom.get().nextLong());
+      keepAlive.setRandomId(threadLocalRandom.nextLong());
       connection.write(keepAlive);
     }
   }