Use JDA's LRU MemberCachePolicy instead of caching everything at startup

src/main/java/ti4/discord/JdaService.java

@@ -19,6 +19,8 @@
 import net.dv8tion.jda.api.entities.Role;
 import net.dv8tion.jda.api.entities.User;
 import net.dv8tion.jda.api.entities.channel.concrete.Category;
+import net.dv8tion.jda.api.exceptions.ErrorResponseException;
+import net.dv8tion.jda.api.requests.ErrorResponse;
 import net.dv8tion.jda.api.requests.GatewayIntent;
 import net.dv8tion.jda.api.requests.restaction.CommandListUpdateAction;
 import net.dv8tion.jda.api.utils.ChunkingFilter;
@@ -109,6 +111,8 @@ public class JdaService {
     public static final List<Guild> serversToCreateNewGamesOn = new ArrayList<>();
     public static final List<Guild> fowServers = new ArrayList<>();
 
+    private static final int MEMBER_CACHE_MAX_SIZE = 20_000;
+
     private static final ExecutorService EVENT_EXECUTOR = Executors.newFixedThreadPool(
             Runtime.getRuntime().availableProcessors(),
             Thread.ofPlatform().name("ti4-jda-event-", 0).factory());
@@ -117,18 +121,16 @@ public static void startJdaAndRegisterListeners(String[] args) {
         BotLogger.info("STARTING JDA");
         jda = JDABuilder.createDefault(args[0])
                 .setEventPool(EVENT_EXECUTOR)
-                // Needed to listen for joins/leaves.
-                // This is required to cache all members of a guild (including chunking)
+                // Needed to listen for joins/leaves and perform targeted member fetches.
                 .enableIntents(GatewayIntent.GUILD_MEMBERS)
                 // Needed to parse raw user messages.
                 .enableIntents(GatewayIntent.MESSAGE_CONTENT)
                 // Needed for emoji searches and validation
                 .enableIntents(GatewayIntent.GUILD_EXPRESSIONS)
-                // It *appears* we need to pull all members or else the bot has trouble pinging players
-                // but that may be a misunderstanding, in case we want to try to use an LRU cache in the future
-                // and avoid loading every user at startup
-                .setMemberCachePolicy(MemberCachePolicy.ALL)
-                .setChunkingFilter(ChunkingFilter.ALL)
+                // Cache up to MEMBER_CACHE_MAX_SIZE most-recently-used members, evicting older
+                // entries automatically. ChunkingFilter.NONE prevents the startup bulk load.
+                .setMemberCachePolicy(MemberCachePolicy.lru(MEMBER_CACHE_MAX_SIZE))
+                .setChunkingFilter(ChunkingFilter.NONE)
                 // This allows us to use our own ShutdownHook, created below
                 .setEnableShutdownHook(false)
                 .build();
@@ -561,13 +563,53 @@ public static boolean isValidGuild(String guildId) {
 
     @Nullable
     public static String getUsername(String userId) {
-        Member member = guildPrimary.getMemberById(userId);
+        Member member = getMemberById(guildPrimary, userId);
         if (member != null) return member.getEffectiveName();
-        User user = jda.getUserById(userId);
+        User user = getUserById(userId);
         if (user != null) return user.getEffectiveName();
         return null;
     }
 
+    /**
+     * Resolves a guild member by user ID. Uses JDA's cache-aware {@code retrieveMemberById}, which
+     * returns the cached member immediately if available, otherwise makes a blocking REST call.
+     * Should only be called from background threads (e.g. ExecutorServiceManager tasks), not from
+     * JDA event-dispatch threads.
+     */
+    @Nullable
+    public static Member getMemberById(@Nullable Guild guild, @Nullable String userId) {
+        if (guild == null || userId == null) return null;
+        try {
+            return guild.retrieveMemberById(userId).complete();
+        } catch (ErrorResponseException e) {
+            if (e.getErrorResponse() != ErrorResponse.UNKNOWN_MEMBER
+                    && e.getErrorResponse() != ErrorResponse.UNKNOWN_USER) {
+                BotLogger.warning(
+                        "Unable to retrieve Discord member `" + userId + "` from guild `" + guild.getId() + "`.", e);
+            }
+            return null;
+        }
+    }
+
+    /**
+     * Resolves a Discord user by user ID. Uses JDA's cache-aware {@code retrieveUserById}, which
+     * returns the cached user immediately if available, otherwise makes a blocking REST call.
+     * Should only be called from background threads (e.g. ExecutorServiceManager tasks), not from
+     * JDA event-dispatch threads.
+     */
+    @Nullable
+    public static User getUserById(@Nullable String userId) {
+        if (jda == null || userId == null) return null;
+        try {
+            return jda.retrieveUserById(userId).complete();
+        } catch (ErrorResponseException e) {
+            if (e.getErrorResponse() != ErrorResponse.UNKNOWN_USER) {
+                BotLogger.warning("Unable to retrieve Discord user `" + userId + "`.", e);
+            }
+            return null;
+        }
+    }
+
     public static void shutdown() {
         try {
             AsyncTI4DiscordBot.markShuttingDown();

src/main/java/ti4/discord/interactions/buttons/handlers/game/CreateGameButtonHandler.java

@@ -156,7 +156,7 @@ private static List<Member> fetchMembersFromMessage(ButtonInteractionEvent event
         for (int i = 0; i < StringUtils.countMatches(buttonMsg, "<@"); i++) {
             String user = buttonMsg.split("@")[i + 1];
             user = StringUtils.substringBefore(user, ">");
-            Member member = event.getGuild().getMemberById(user);
+            Member member = JdaService.getMemberById(event.getGuild(), user);
             if (member != null) {
                 members.add(member);
             }
@@ -170,7 +170,7 @@ private static List<Member> fetchMembersFromMessage(ModalInteractionEvent event)
         for (int i = 0; i < StringUtils.countMatches(buttonMsg, "<@"); i++) {
             String user = buttonMsg.split("@")[i + 1];
             user = StringUtils.substringBefore(user, ">");
-            Member member = event.getGuild().getMemberById(user);
+            Member member = JdaService.getMemberById(event.getGuild(), user);
             if (member != null) {
                 members.add(member);
             }
@@ -400,7 +400,7 @@ private static List<Member> parseMembersFromButtonMessage(ButtonInteractionEvent
 
         for (int i = 3; i < parts.length; i++) {
             String userId = StringUtils.substringBefore(parts[i], ".");
-            Member member = event.getGuild().getMemberById(userId);
+            Member member = JdaService.getMemberById(event.getGuild(), userId);
             if (member != null) {
                 members.add(member);
             }

src/main/java/ti4/discord/interactions/commands/bothelper/CreateFOWGameChannels.java

@@ -1,8 +1,8 @@
 package ti4.discord.interactions.commands.bothelper;
 
+import ti4.discord.JdaService;
 import java.util.List;
 import net.dv8tion.jda.api.entities.Guild;
-import net.dv8tion.jda.api.entities.ISnowflake;
 import net.dv8tion.jda.api.entities.Member;
 import net.dv8tion.jda.api.events.interaction.command.SlashCommandInteractionEvent;
 import net.dv8tion.jda.api.interactions.commands.OptionType;
@@ -53,12 +53,10 @@ public void execute(SlashCommandInteractionEvent event) {
         }
 
         // CHECK IF GUILD HAS ALL PLAYERS LISTED
-        List<String> guildMemberIDs =
-                guild.getMembers().stream().map(ISnowflake::getId).toList();
         boolean sendInviteLink = false;
         int count = 0;
         for (Member member : members) {
-            if (!guildMemberIDs.contains(member.getId())) {
+            if (JdaService.getMemberById(guild, member.getId()) == null) {
                 MessageHelper.sendMessageToEventChannel(
                         event,
                         member.getAsMention() + " is not a member of the server **" + guild.getName()

src/main/java/ti4/discord/interactions/commands/event/LookAtBottomEvent.java

@@ -1,5 +1,6 @@
 package ti4.discord.interactions.commands.event;
 
+import ti4.discord.JdaService;
 import net.dv8tion.jda.api.entities.User;
 import net.dv8tion.jda.api.events.interaction.command.SlashCommandInteractionEvent;
 import net.dv8tion.jda.api.interactions.commands.OptionMapping;
@@ -44,7 +45,7 @@ public void execute(SlashCommandInteractionEvent event) {
         sb.append("-----------\n");
 
         Player player = getPlayer();
-        User userById = event.getJDA().getUserById(player.getUserID());
+        User userById = JdaService.getUserById(player.getUserID());
         if (userById != null) {
             if (game.isCommunityMode() && player.getPrivateChannel() != null) {
                 MessageHelper.sendMessageToChannel(player.getPrivateChannel(), sb.toString());

src/main/java/ti4/discord/interactions/commands/event/LookAtTopEvent.java

@@ -1,5 +1,6 @@
 package ti4.discord.interactions.commands.event;
 
+import ti4.discord.JdaService;
 import net.dv8tion.jda.api.entities.User;
 import net.dv8tion.jda.api.events.interaction.command.SlashCommandInteractionEvent;
 import net.dv8tion.jda.api.interactions.commands.OptionMapping;
@@ -45,7 +46,7 @@ public void execute(SlashCommandInteractionEvent event) {
         sb.append("-----------\n");
 
         Player player = getPlayer();
-        User userById = event.getJDA().getUserById(player.getUserID());
+        User userById = JdaService.getUserById(player.getUserID());
         if (userById != null) {
             if (game.isCommunityMode() && player.getPrivateChannel() != null) {
                 MessageHelper.sendMessageToChannel(player.getPrivateChannel(), sb.toString());

src/main/java/ti4/discord/interactions/commands/game/Observer.java

@@ -1,5 +1,6 @@
 package ti4.discord.interactions.commands.game;
 
+import ti4.discord.JdaService;
 import java.util.ArrayList;
 import java.util.List;
 import net.dv8tion.jda.api.Permission;
@@ -52,10 +53,10 @@ public void execute(SlashCommandInteractionEvent event) {
 
         ManagedGame game = GameManager.getManagedGame(gameName);
         Guild guild = game.getGuild();
-        Member member = guild.getMemberById(user.getId());
+        Member member = JdaService.getMemberById(guild, user.getId());
 
         if (member == null && event.getGuild() != null) {
-            member = event.getGuild().getMemberById(user.getId());
+            member = JdaService.getMemberById(event.getGuild(), user.getId());
         }
 
         // INVITE TO GAME SERVER IF MISSING
@@ -101,7 +102,7 @@ private void addObserver(
             SlashCommandInteractionEvent event, String userID, GuildChannel channel, boolean skipMessage) {
         if (channel == null) return;
         Guild guild = channel.getGuild();
-        Member user = guild.getMemberById(userID);
+        Member user = JdaService.getMemberById(guild, userID);
         channel.getPermissionContainer()
                 .upsertPermissionOverride(user)
                 .grant(Permission.VIEW_CHANNEL, Permission.MESSAGE_SEND)
@@ -121,7 +122,7 @@ private void removeObserver(
         // This resets the member's perms to the default value,
         //   -> -> ->  SO IF THE USER IS IN THE GAME, THEY DON'T GET REMOVED
         Guild guild = channel.getGuild();
-        Member user = guild.getMemberById(userID);
+        Member user = JdaService.getMemberById(guild, userID);
         channel.getPermissionContainer()
                 .upsertPermissionOverride(user)
                 .clear(Permission.VIEW_CHANNEL, Permission.MESSAGE_SEND)

src/main/java/ti4/discord/interactions/commands/game/Replace.java

@@ -86,14 +86,14 @@ public void execute(SlashCommandInteractionEvent event) {
         if (guild == null) {
             guild = event.getGuild();
         }
-        Member newMember = guild.getMemberById(replacementUser.getId());
+        Member newMember = JdaService.getMemberById(guild, replacementUser.getId());
         if (newMember == null) {
             MessageHelper.replyToMessage(event, "Added player must be on the game's server.");
             return;
         }
 
         // REMOVE ROLE
-        Member oldMember = guild.getMemberById(replacedPlayer.getUserID());
+        Member oldMember = JdaService.getMemberById(guild, replacedPlayer.getUserID());
         List<Role> roles = guild.getRolesByName(game.getName(), true);
         if (oldMember != null && roles.size() == 1) {
             guild.removeRoleFromMember(oldMember, roles.getFirst()).queue(Consumers.nop(), BotLogger::catchRestError);

src/main/java/ti4/discord/interactions/commands/player/RemoveAllianceMember.java

@@ -44,11 +44,11 @@ public void execute(SlashCommandInteractionEvent event) {
         }
 
         player.getCardsInfoThread()
-                .removeThreadMember(JdaService.jda.getUserById(targetPlayer.getUserID()))
+                .removeThreadMember(JdaService.getUserById(targetPlayer.getUserID()))
                 .queue(Consumers.nop(), BotLogger::catchRestError);
         targetPlayer
                 .getCardsInfoThread()
-                .removeThreadMember(JdaService.jda.getUserById(player.getUserID()))
+                .removeThreadMember(JdaService.getUserById(player.getUserID()))
                 .queue(Consumers.nop(), BotLogger::catchRestError);
 
         MessageHelper.sendMessageToEventChannel(

src/main/java/ti4/discord/interactions/commands/player/Stats.java

@@ -1,5 +1,6 @@
 package ti4.discord.interactions.commands.player;
 
+import ti4.discord.JdaService;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
@@ -343,7 +344,7 @@ public void execute(SlashCommandInteractionEvent event) {
                 UserSettingsManager.save(userSettings);
 
                 Guild guild = event.getGuild();
-                Member removedMember = guild.getMemberById(player.getUserID());
+                Member removedMember = JdaService.getMemberById(guild, player.getUserID());
                 List<Role> roles = guild.getRolesByName(game.getName(), true);
                 if (removedMember != null && roles.size() == 1) {
                     guild.removeRoleFromMember(removedMember, roles.getFirst())

src/main/java/ti4/discord/interactions/listeners/AutoCompleteProvider.java

@@ -1056,7 +1056,7 @@ private static void handleOptions(
                 DraftManager draftManager = game.getDraftManager();
                 String enteredValue = event.getFocusedOption().getValue().toLowerCase();
                 Predicate<String> isUnknownUserId =
-                        id -> game.getPlayer(id) == null || event.getGuild().getMemberById(id) == null;
+                        id -> game.getPlayer(id) == null || JdaService.getMemberById(event.getGuild(), id) == null;
                 List<String> userIDs = draftManager.getPlayerUserIds().stream()
                         .filter(isUnknownUserId)
                         .toList();

src/main/java/ti4/game/Game.java

@@ -3650,7 +3650,7 @@ public String getPing() {
         }
         StringBuilder sb = new StringBuilder(getName()).append(' ');
         for (String playerID : getPlayerIDs()) {
-            User user = JdaService.jda.getUserById(playerID);
+            User user = JdaService.getUserById(playerID);
             if (user != null) sb.append(user.getAsMention()).append(' ');
         }
         return sb.toString();
@@ -3771,7 +3771,7 @@ public List<Player> getPlayersWithGMRole() {
         Role gmRole = roles.isEmpty() ? null : roles.getFirst();
         return players.values().stream()
                 .filter(player -> {
-                    Member user = getGuild().getMemberById(player.getUserID());
+                    Member user = JdaService.getMemberById(getGuild(), player.getUserID());
                     return user != null && user.getRoles().contains(gmRole);
                 })
                 .toList();

src/main/java/ti4/game/Player.java

@@ -1512,7 +1512,7 @@ public Member getMember() {
         if (game == null) return null;
         Guild guild = game.getGuild();
         if (guild == null) return null;
-        return guild.getMemberById(getUserID());
+        return JdaService.getMemberById(guild, getUserID());
     }
 
     public User getUser() {
@@ -1521,7 +1521,7 @@ public User getUser() {
 
     private User getUser(String userId) {
         // TODO: This is to handle JDA being null during tests. We should think of a cleaner solution.
-        return JdaService.jda == null ? null : JdaService.jda.getUserById(userId);
+        return JdaService.jda == null ? null : JdaService.getUserById(userId);
     }
 
     @Override
@@ -1538,7 +1538,7 @@ public String getUserName() {
         User userById = getUser();
         if (userById == null) return super.getUserName();
 
-        Member member = JdaService.guildPrimary.getMemberById(getUserID());
+        Member member = JdaService.getMemberById(JdaService.guildPrimary, getUserID());
         if (member == null) {
             setUserName(userById.getName());
         } else {
@@ -1605,7 +1605,7 @@ public String getRepresentation(boolean overrideFow, boolean ping, boolean noCol
             if (roleForCommunity == null && !getTeamMateIDs().isEmpty()) {
                 StringBuilder sb = new StringBuilder((noFactionIcon ? "" : getFactionEmoji()));
                 for (String userID : getTeamMateIDs()) {
-                    User userById = JdaService.jda.getUserById(userID);
+                    User userById = JdaService.getUserById(userID);
                     if (userById == null) {
                         continue;
                     }

src/main/java/ti4/helpers/ButtonHelper.java

@@ -1,5 +1,6 @@
 package ti4.helpers;
 
+import ti4.discord.JdaService;
 import static org.apache.commons.lang3.StringUtils.countMatches;
 import static org.apache.commons.lang3.StringUtils.isNotBlank;
 import static org.apache.commons.lang3.StringUtils.substringAfter;
@@ -930,7 +931,7 @@ public static void removeUser(
         }
 
         Guild guild = event.getGuild();
-        Member removedMember = guild.getMemberById(player.getUserID());
+        Member removedMember = JdaService.getMemberById(guild, player.getUserID());
         List<Role> roles = guild.getRolesByName(game.getName(), true);
         if (removedMember != null && roles.size() == 1) {
             guild.removeRoleFromMember(removedMember, roles.getFirst())
@@ -8391,7 +8392,7 @@ public static void sendMessageToRightStratThread(
         String threadName = game.getName() + "-round-" + game.getRound() + "-" + stratName.toLowerCase();
         for (ThreadChannel threadChannel_ : threadChannels) {
             if ("pbd1000".equalsIgnoreCase(game.getName()) || "pbd100two".equalsIgnoreCase(game.getName())) {
-                if (!threadChannel_.getMembers().contains(game.getGuild().getMemberById(player.getUserID()))) {
+                if (!threadChannel_.getMembers().contains(JdaService.getMemberById(game.getGuild(), player.getUserID()))) {
                     continue;
                 }
             }

src/main/java/ti4/helpers/GameLaunchThreadHelper.java

@@ -1,10 +1,8 @@
 package ti4.helpers;
 
-import java.util.List;
 import java.util.concurrent.TimeUnit;
 import lombok.experimental.UtilityClass;
 import net.dv8tion.jda.api.entities.Guild;
-import net.dv8tion.jda.api.entities.ISnowflake;
 import net.dv8tion.jda.api.entities.channel.concrete.ThreadChannel;
 import ti4.discord.JdaService;
 import ti4.game.Game;
@@ -26,10 +24,8 @@ public static void checkIfCanCloseGameLaunchThread(Game game, boolean notify) {
         if (threadChannel == null) {
             return;
         }
-        List<String> guildMemberIDs =
-                guild.getMembers().stream().map(ISnowflake::getId).toList();
         for (String playerIds : game.getPlayerIDs()) {
-            if (!guildMemberIDs.contains(playerIds)) {
+            if (JdaService.getMemberById(guild, playerIds) == null) {
                 return;
             }
         }