Rewrite User storage and UUID cache (#4581)

Co-authored-by: triagonal <10545540+triagonal@users.noreply.github.com>
Co-authored-by: MD <1917406+mdcfe@users.noreply.github.com>

.gitignore

@@ -15,6 +15,8 @@
 /Essentials/kits.yml
 /Essentials/userdata/testplayer1.yml
 /Essentials/usermap.csv
+/Essentials/usermap.bin
+/Essentials/uuids.bin
 
 # Build files
 .gradle/

Essentials/src/main/java/com/earth2me/essentials/BalanceTopImpl.java

@@ -28,8 +28,8 @@ public class BalanceTopImpl implements BalanceTop {
     private void calculateBalanceTopMap() {
         final List<Entry> entries = new LinkedList<>();
         BigDecimal newTotal = BigDecimal.ZERO;
-        for (UUID u : ess.getUserMap().getAllUniqueUsers()) {
+        for (UUID u : ess.getUsers().getAllUserUUIDs()) {
-            final User user = ess.getUserMap().getUser(u);
+            final User user = ess.getUsers().loadUncachedUser(u);
             if (user != null) {
                 if (!ess.getSettings().isNpcsInBalanceRanking() && user.isNPC()) {
                     // Don't list NPCs in output

Essentials/src/main/java/com/earth2me/essentials/Essentials.java

@@ -39,6 +39,7 @@ import com.earth2me.essentials.textreader.IText;
 import com.earth2me.essentials.textreader.KeywordReplacer;
 import com.earth2me.essentials.textreader.SimpleTextInput;
 import com.earth2me.essentials.updatecheck.UpdateChecker;
+import com.earth2me.essentials.userstorage.ModernUserMap;
 import com.earth2me.essentials.utils.FormatUtil;
 import com.earth2me.essentials.utils.VersionUtil;
 import io.papermc.lib.PaperLib;
@@ -155,7 +156,9 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
     private transient CustomItemResolver customItemResolver;
     private transient PermissionsHandler permissionsHandler;
     private transient AlternativeCommandsHandler alternativeCommandsHandler;
-    private transient UserMap userMap;
+    @Deprecated
+    private transient UserMap legacyUserMap;
+    private transient ModernUserMap userMap;
     private transient BalanceTopImpl balanceTop;
     private transient ExecuteTimer execTimer;
     private transient MailService mail;
@@ -222,7 +225,7 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
         LOGGER.log(Level.INFO, dataFolder.toString());
         settings = new Settings(this);
         mail = new MailServiceImpl(this);
-        userMap = new UserMap(this);
+        userMap = new ModernUserMap(this);
         balanceTop = new BalanceTopImpl(this);
         permissionsHandler = new PermissionsHandler(this, false);
         Economy.setEss(this);
@@ -301,11 +304,14 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
             confList.add(settings);
             execTimer.mark("Settings");
 
+            upgrade.preModules();
+            execTimer.mark("Upgrade2");
+
             mail = new MailServiceImpl(this);
             execTimer.mark("Init(Mail)");
 
-            userMap = new UserMap(this);
+            userMap = new ModernUserMap(this);
-            confList.add(userMap);
+            legacyUserMap = new UserMap(userMap);
             execTimer.mark("Init(Usermap)");
 
             balanceTop = new BalanceTopImpl(this);
@@ -317,7 +323,7 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
             execTimer.mark("Kits");
 
             upgrade.afterSettings();
-            execTimer.mark("Upgrade2");
+            execTimer.mark("Upgrade3");
 
             warps = new Warps(this.getDataFolder());
             confList.add(warps);
@@ -588,7 +594,7 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
 
         Economy.setEss(null);
         Trade.closeLog();
-        getUserMap().getUUIDMap().shutdown();
+        getUsers().shutdown();
 
         HandlerList.unregisterAll(this);
     }
@@ -1067,7 +1073,7 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
             if (getSettings().isDebug()) {
                 LOGGER.log(Level.INFO, "Constructing new userfile from base player " + base.getName());
             }
-            user = new User(base, this);
+            user = userMap.loadUncachedUser(base);
         } else {
             user.update(base);
         }
@@ -1203,7 +1209,13 @@ public class Essentials extends JavaPlugin implements net.ess3.api.IEssentials {
     }
 
     @Override
+    @Deprecated
     public UserMap getUserMap() {
+        return legacyUserMap;
+    }
+
+    @Override
+    public ModernUserMap getUsers() {
         return userMap;
     }
 

Essentials/src/main/java/com/earth2me/essentials/EssentialsPlayerListener.java

@@ -308,6 +308,7 @@ public class EssentialsPlayerListener implements Listener, FakeAccessor {
 
         ess.getBackup().onPlayerJoin();
         final User dUser = ess.getUser(player);
+        dUser.update(player);
 
         dUser.startTransaction();
         if (dUser.isNPC()) {
@@ -367,7 +368,7 @@ public class EssentialsPlayerListener implements Listener, FakeAccessor {
                 } else if (ess.getSettings().isCustomJoinMessage()) {
                     final String msg = (newUsername ? ess.getSettings().getCustomNewUsernameMessage() : ess.getSettings().getCustomJoinMessage())
                         .replace("{PLAYER}", player.getDisplayName()).replace("{USERNAME}", player.getName())
-                        .replace("{UNIQUE}", NumberFormat.getInstance().format(ess.getUserMap().getUniqueUsers()))
+                        .replace("{UNIQUE}", NumberFormat.getInstance().format(ess.getUsers().getUserCount()))
                         .replace("{ONLINE}", NumberFormat.getInstance().format(ess.getOnlinePlayers().size()))
                         .replace("{UPTIME}", DateUtil.formatDateDiff(ManagementFactory.getRuntimeMXBean().getStartTime()))
                         .replace("{PREFIX}", FormatUtil.replaceFormat(ess.getPermissionsHandler().getPrefix(player)))
@@ -527,6 +528,7 @@ public class EssentialsPlayerListener implements Listener, FakeAccessor {
     public void onPlayerLogin(final PlayerLoginEvent event) {
         if (event.getResult() == Result.KICK_FULL) {
             final User kfuser = ess.getUser(event.getPlayer());
+            kfuser.update(event.getPlayer());
             if (kfuser.isAuthorized("essentials.joinfullserver")) {
                 event.allow();
                 return;

Essentials/src/main/java/com/earth2me/essentials/EssentialsUpgrade.java

@@ -4,9 +4,9 @@ import com.earth2me.essentials.config.ConfigurateUtil;
 import com.earth2me.essentials.config.EssentialsConfiguration;
 import com.earth2me.essentials.config.EssentialsUserConfiguration;
 import com.earth2me.essentials.craftbukkit.BanLookup;
+import com.earth2me.essentials.userstorage.ModernUUIDCache;
 import com.earth2me.essentials.utils.StringUtil;
 import com.google.common.base.Charsets;
-import com.google.common.collect.Maps;
 import com.google.common.io.Files;
 import com.google.gson.reflect.TypeToken;
 import net.ess3.api.IEssentials;
@@ -31,10 +31,10 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.security.DigestInputStream;
 import java.security.MessageDigest;
-import java.text.DecimalFormat;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
@@ -47,13 +47,12 @@ import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
-import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import static com.earth2me.essentials.I18n.tl;
 
 public class EssentialsUpgrade {
-    private static final FileFilter YML_FILTER = pathname -> pathname.isFile() && pathname.getName().endsWith(".yml");
+    public static final FileFilter YML_FILTER = pathname -> pathname.isFile() && pathname.getName().endsWith(".yml");
     private static final String PATTERN_CONFIG_UUID_REGEX = "(?mi)^uuid:\\s*([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})\\s*$";
     private static final Pattern PATTERN_CONFIG_UUID = Pattern.compile(PATTERN_CONFIG_UUID_REGEX);
     private static final String PATTERN_CONFIG_NAME_REGEX = "(?mi)^lastAccountName:\\s*[\"\']?(\\w+)[\"\']?\\s*$";
@@ -93,7 +92,6 @@ public class EssentialsUpgrade {
             final int showProgress = countFiles % 250;
 
             if (showProgress == 0) {
-                ess.getUserMap().getUUIDMap().forceWriteUUIDMap();
                 ess.getLogger().info("Converted " + countFiles + "/" + userdir.list().length);
             }
 
@@ -103,7 +101,8 @@ public class EssentialsUpgrade {
             final EssentialsUserConfiguration config;
             UUID uuid = null;
             try {
-                uuid = UUID.fromString(name);
+                //noinspection ResultOfMethodCallIgnored
+                UUID.fromString(name);
             } catch (final IllegalArgumentException ex) {
                 final File file = new File(userdir, string);
                 final EssentialsConfiguration conf = new EssentialsConfiguration(file);
@@ -115,6 +114,7 @@ public class EssentialsUpgrade {
 
                 final String uuidString = conf.getString(uuidConf, null);
 
+                //noinspection ConstantConditions
                 for (int i = 0; i < 4; i++) {
                     try {
                         uuid = UUID.fromString(uuidString);
@@ -122,7 +122,7 @@ public class EssentialsUpgrade {
                         break;
                     } catch (final Exception ex2) {
                         if (conf.getBoolean("npc", false)) {
-                            uuid = UUID.nameUUIDFromBytes(("NPC:" + name).getBytes(Charsets.UTF_8));
+                            uuid = UUID.nameUUIDFromBytes(("NPC:" + (ess.getSettings().isSafeUsermap() ? StringUtil.safeString(name) : name)).getBytes(Charsets.UTF_8));
                             break;
                         }
 
@@ -130,23 +130,24 @@ public class EssentialsUpgrade {
                         uuid = player.getUniqueId();
                     }
 
+                    //noinspection ConstantConditions
                     if (uuid != null) {
                         countBukkit++;
                         break;
                     }
                 }
 
+                //noinspection ConstantConditions
                 if (uuid != null) {
                     conf.blockingSave();
                     config = new EssentialsUserConfiguration(name, uuid, new File(userdir, uuid + ".yml"));
                     config.convertLegacyFile();
-                    ess.getUserMap().trackUUID(uuid, name, false);
+                    ess.getUsers().loadUncachedUser(uuid);
                     continue;
                 }
                 countFails++;
             }
         }
-        ess.getUserMap().getUUIDMap().forceWriteUUIDMap();
 
         ess.getLogger().info("Converted " + countFiles + "/" + countFiles + ".  Conversion complete.");
         ess.getLogger().info("Converted via cache: " + countEssCache + " :: Converted via lookup: " + countBukkit + " :: Failed to convert: " + countFails);
@@ -913,74 +914,76 @@ public class EssentialsUpgrade {
         Bukkit.getBanList(BanList.Type.NAME).addBan(playerName, banReason, banTimeout == 0 ? null : new Date(banTimeout), Console.NAME);
     }
 
-    private void repairUserMap() {
+    public void generateUidCache() {
-        if (doneFile.getBoolean("userMapRepaired", false)) {
+        if (doneFile.getBoolean("newUidCacheBuilt", false)) {
             return;
         }
-        ess.getLogger().info("Starting usermap repair");
 
+        final File usermapFile = new File(ess.getDataFolder(), "usermap.bin");
+        final File uidsFile = new File(ess.getDataFolder(), "uuids.bin");
         final File userdataFolder = new File(ess.getDataFolder(), "userdata");
-        if (!userdataFolder.isDirectory()) {
+
+        if (!userdataFolder.isDirectory() || usermapFile.exists() || uidsFile.exists()) {
             ess.getLogger().warning("Missing userdata folder, aborting");
+            doneFile.setProperty("newUidCacheBuilt", true);
+            doneFile.save();
             return;
         }
+
+        try {
+            if (!usermapFile.createNewFile() || !uidsFile.createNewFile()) {
+                ess.getLogger().warning("Couldn't create usermap.bin or uuids.bin, aborting");
+                return;
+            }
+
+            final Map<UUID, Long> uuids = new HashMap<>();
+            final Map<String, UUID> nameToUuidMap = new HashMap<>();
+
             final File[] files = userdataFolder.listFiles(YML_FILTER);
-
+            if (files != null) {
-        final DecimalFormat format = new DecimalFormat("#0.00");
+                for (final File file : files) {
-        final Map<String, UUID> names = Maps.newHashMap();
-
-        for (int index = 0; index < files.length; index++) {
-            final File file = files[index];
                     try {
-                UUID uuid = null;
+                        final String fileName = file.getName();
-                final String filename = file.getName();
+                        final UUID uuid = UUID.fromString(fileName.substring(0, fileName.length() - 4));
-                final String configData = new String(java.nio.file.Files.readAllBytes(file.toPath()), Charsets.UTF_8);
+                        final EssentialsConfiguration config = new EssentialsConfiguration(file);
+                        config.load();
+                        String name = config.getString("last-account-name", null);
+                        name = ess.getSettings().isSafeUsermap() ? StringUtil.safeString(name) : name;
+                        final long time = config.getLong("timestamps.logout", 0L);
 
-                if (filename.length() > 36) {
+                        if (name != null) {
-                    try {
+                            if (nameToUuidMap.containsKey(name)) {
-                        // ".yml" ending has 4 chars...
+                                final UUID oldUuid = nameToUuidMap.get(name);
-                        uuid = UUID.fromString(filename.substring(0, filename.length() - 4));
+                                if (oldUuid.version() < uuid.version() || (oldUuid.version() == uuid.version() && uuids.get(oldUuid) < time)) {
-                    } catch (final IllegalArgumentException ignored) {
+                                    ess.getLogger().warning("New UUID found for " + name + ": " + uuid + " (old: " + oldUuid + "). Replacing.");
-                    }
+                                    uuids.remove(oldUuid);
-                }
+                                } else {
-
+                                    ess.getLogger().warning("Found UUID for " + name + ": " + uuid + " (old: " + oldUuid + "). Skipping.");
-                final Matcher uuidMatcher = PATTERN_CONFIG_UUID.matcher(configData);
-                if (uuidMatcher.find()) {
-                    try {
-                        uuid = UUID.fromString(uuidMatcher.group(1));
-                    } catch (final IllegalArgumentException ignored) {
-                    }
-                }
-
-                if (uuid == null) {
-                    // Don't import
                                     continue;
                                 }
+                            }
 
-                final Matcher nameMatcher = PATTERN_CONFIG_NAME.matcher(configData);
+                            uuids.put(uuid, config.getLong("timestamps.logout", 0L));
-                if (nameMatcher.find()) {
+                            nameToUuidMap.put(name, uuid);
-                    final String username = nameMatcher.group(1);
+                        }
-                    if (username != null && username.length() > 0) {
+                    } catch (IllegalArgumentException | IndexOutOfBoundsException ignored) {
-                        names.put(StringUtil.safeString(username), uuid);
+                    }
                 }
             }
 
-                if (index % 1000 == 0) {
+            if (!nameToUuidMap.isEmpty()) {
-                    ess.getLogger().info("Reading: " + format.format((100d * (double) index) / files.length)
+                ModernUUIDCache.writeNameUuidMap(usermapFile, nameToUuidMap);
-                        + "%");
-                }
-            } catch (final IOException e) {
-                ess.getLogger().log(Level.SEVERE, "Error while reading file: ", e);
-                return;
-            }
             }
 
-        ess.getUserMap().getNames().putAll(names);
+            if (!uuids.isEmpty()) {
-        ess.getUserMap().reloadConfig();
+                ModernUUIDCache.writeUuidCache(uidsFile, uuids.keySet());
+            }
 
-        doneFile.setProperty("userMapRepaired", true);
+            doneFile.setProperty("newUidCacheBuilt", true);
             doneFile.save();
-        ess.getLogger().info("Completed usermap repair.");
+        } catch (final IOException e) {
+            ess.getLogger().log(Level.SEVERE, "Error while generating initial uuids/names cache", e);
+        }
     }
 
     public void beforeSettings() {
@@ -991,6 +994,10 @@ public class EssentialsUpgrade {
         moveMotdRulesToFile("rules");
     }
 
+    public void preModules() {
+        generateUidCache();
+    }
+
     public void afterSettings() {
         sanitizeAllUserFilenames();
         updateUsersPowerToolsFormat();
@@ -1001,7 +1008,6 @@ public class EssentialsUpgrade {
         uuidFileChange();
         banFormatChange();
         warnMetrics();
-        repairUserMap();
         convertIgnoreList();
         convertStupidCamelCaseUserdataKeys();
         convertMailList();

Essentials/src/main/java/com/earth2me/essentials/IEssentials.java

@@ -7,6 +7,7 @@ import com.earth2me.essentials.commands.IEssentialsCommand;
 import com.earth2me.essentials.commands.PlayerNotFoundException;
 import com.earth2me.essentials.perm.PermissionsHandler;
 import com.earth2me.essentials.updatecheck.UpdateChecker;
+import com.earth2me.essentials.userstorage.IUserMap;
 import net.ess3.nms.refl.providers.ReflOnlineModeProvider;
 import net.ess3.provider.ContainerProvider;
 import net.ess3.provider.FormattedCommandAliasProvider;
@@ -119,6 +120,9 @@ public interface IEssentials extends Plugin {
 
     IItemDb getItemDb();
 
+    IUserMap getUsers();
+
+    @Deprecated
     UserMap getUserMap();
 
     BalanceTop getBalanceTop();

Essentials/src/main/java/com/earth2me/essentials/IUser.java

@@ -330,4 +330,8 @@ public interface IUser {
             this.time = time;
         }
     }
+
+    List<String> getPastUsernames();
+
+    void addPastUsername(String username);
 }

Essentials/src/main/java/com/earth2me/essentials/UUIDMap.java

@@ -1,155 +1,19 @@
 package com.earth2me.essentials;
 
-import com.google.common.io.Files;
+@Deprecated
-
-import java.io.BufferedReader;
-import java.io.BufferedWriter;
-import java.io.File;
-import java.io.FileReader;
-import java.io.FileWriter;
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.UUID;
-import java.util.concurrent.ConcurrentSkipListMap;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
-import java.util.logging.Level;
-import java.util.regex.Pattern;
-
 public class UUIDMap {
-    private static final ScheduledExecutorService writeScheduler = Executors.newScheduledThreadPool(1);
+    public UUIDMap() {
-    private static boolean pendingWrite;
-    private static boolean loading = false;
-    private final transient net.ess3.api.IEssentials ess;
-    private final File userList;
-    private final transient Pattern splitPattern = Pattern.compile(",");
-    private final Runnable writeTaskRunnable;
-
-    public UUIDMap(final net.ess3.api.IEssentials ess) {
-        this.ess = ess;
-        userList = new File(ess.getDataFolder(), "usermap.csv");
-        pendingWrite = false;
-        writeTaskRunnable = () -> {
-            if (pendingWrite) {
-                try {
-                    new WriteRunner(ess.getDataFolder(), userList, ess.getUserMap().getNames()).run();
-                } catch (final Throwable t) { // bad code to prevent task from being suppressed
-                    t.printStackTrace();
-                }
-            }
-        };
-        writeScheduler.scheduleWithFixedDelay(writeTaskRunnable, 5, 5, TimeUnit.SECONDS);
-    }
-
-    public void loadAllUsers(final ConcurrentSkipListMap<String, UUID> names, final ConcurrentSkipListMap<UUID, ArrayList<String>> history) {
-        try {
-            if (!userList.exists()) {
-                userList.createNewFile();
-            }
-
-            if (ess.getSettings().isDebug()) {
-                ess.getLogger().log(Level.INFO, "Reading usermap from disk");
-            }
-
-            if (loading) {
-                return;
-            }
-
-            names.clear();
-            history.clear();
-            loading = true;
-
-            try (final BufferedReader reader = new BufferedReader(new FileReader(userList))) {
-                while (true) {
-                    final String line = reader.readLine();
-                    if (line == null) {
-                        break;
-                    } else {
-                        final String[] values = splitPattern.split(line);
-                        if (values.length == 2) {
-                            final String name = values[0];
-                            final UUID uuid = UUID.fromString(values[1]);
-                            names.put(name, uuid);
-                            if (!history.containsKey(uuid)) {
-                                final ArrayList<String> list = new ArrayList<>();
-                                list.add(name);
-                                history.put(uuid, list);
-                            } else {
-                                final ArrayList<String> list = history.get(uuid);
-                                if (!list.contains(name)) {
-                                    list.add(name);
-                                }
-                            }
-                        }
-                    }
-                }
-            }
-            loading = false;
-        } catch (final IOException ex) {
-            Essentials.getWrappedLogger().log(Level.SEVERE, ex.getMessage(), ex);
-        }
     }
 
     public void writeUUIDMap() {
-        pendingWrite = true;
+        //no-op
     }
 
     public void forceWriteUUIDMap() {
-        if (ess.getSettings().isDebug()) {
+        //no-op
-            ess.getLogger().log(Level.INFO, "Forcing usermap write to disk");
-        }
-        pendingWrite = true;
-        writeTaskRunnable.run();
     }
 
     public void shutdown() {
-        writeScheduler.submit(writeTaskRunnable);
+        //no-op
-        writeScheduler.shutdown();
-    }
-
-    private static final class WriteRunner implements Runnable {
-        private final File location;
-        private final File endFile;
-        private final Map<String, UUID> names;
-
-        private WriteRunner(final File location, final File endFile, final Map<String, UUID> names) {
-            this.location = location;
-            this.endFile = endFile;
-            this.names = new HashMap<>(names);
-        }
-
-        @Override
-        public void run() {
-            pendingWrite = false;
-            if (loading || names.isEmpty()) {
-                return;
-            }
-            File configFile = null;
-
-            try {
-                configFile = File.createTempFile("usermap", ".tmp.csv", location);
-
-                final BufferedWriter bWriter = new BufferedWriter(new FileWriter(configFile));
-                for (final Map.Entry<String, UUID> entry : names.entrySet()) {
-                    bWriter.write(entry.getKey() + "," + entry.getValue().toString());
-                    bWriter.newLine();
-                }
-
-                bWriter.close();
-                Files.move(configFile, endFile);
-            } catch (final IOException ex) {
-                try {
-                    if (configFile != null && configFile.exists()) {
-                        Files.move(configFile, new File(endFile.getParentFile(), "usermap.bak.csv"));
-                    }
-                } catch (final Exception ex2) {
-                    Essentials.getWrappedLogger().log(Level.SEVERE, ex2.getMessage(), ex2);
-                }
-                Essentials.getWrappedLogger().log(Level.WARNING, ex.getMessage(), ex);
-            }
-        }
     }
 }

Essentials/src/main/java/com/earth2me/essentials/User.java

@@ -106,7 +106,7 @@ public class User extends UserData implements Comparable<User>, IMessageRecipien
         this.messageRecipient = new SimpleMessageRecipient(ess, this);
     }
 
-    void update(final Player base) {
+    public void update(final Player base) {
         setBase(base);
     }
 

Essentials/src/main/java/com/earth2me/essentials/UserData.java

@@ -5,6 +5,7 @@ import com.earth2me.essentials.config.EssentialsUserConfiguration;
 import com.earth2me.essentials.config.entities.CommandCooldown;
 import com.earth2me.essentials.config.entities.LazyLocation;
 import com.earth2me.essentials.config.holders.UserConfigHolder;
+import com.earth2me.essentials.userstorage.ModernUserMap;
 import com.earth2me.essentials.utils.NumberUtil;
 import com.earth2me.essentials.utils.StringUtil;
 import com.google.common.base.Charsets;
@@ -43,19 +44,14 @@ public abstract class UserData extends PlayerExtension implements IConf {
         super(base);
         this.ess = ess;
         final File folder = new File(ess.getDataFolder(), "userdata");
-        if (!folder.exists()) {
+        if (!folder.exists() && !folder.mkdirs()) {
-            folder.mkdirs();
+            throw new RuntimeException("Unable to create userdata folder!");
         }
 
-        String filename;
+        config = new EssentialsUserConfiguration(base.getName(), base.getUniqueId(), new File(folder, base.getUniqueId() + ".yml"));
-        try {
+        config.setSaveHook(() -> {
-            filename = base.getUniqueId().toString();
+            config.setRootHolder(UserConfigHolder.class, holder);
-        } catch (final Throwable ex) {
+        });
-            ess.getLogger().warning("Falling back to old username system for " + base.getName());
-            filename = base.getName();
-        }
-
-        config = new EssentialsUserConfiguration(base.getName(), base.getUniqueId(), new File(folder, filename + ".yml"));
         reloadConfig();
 
         if (config.getUsername() == null) {
@@ -65,12 +61,15 @@ public abstract class UserData extends PlayerExtension implements IConf {
 
     public final void reset() {
         config.blockingSave();
-        config.getFile().delete();
+        if (!config.getFile().delete()) {
+            ess.getLogger().warning("Unable to delete data file for " + config.getFile().getName());
+        }
         if (config.getUsername() != null) {
-            ess.getUserMap().removeUser(config.getUsername());
+            final ModernUserMap users = (ModernUserMap) ess.getUsers();
+            users.invalidate(config.getUuid());
             if (isNPC()) {
-                final String uuid = UUID.nameUUIDFromBytes(("NPC:" + StringUtil.safeString(config.getUsername())).getBytes(Charsets.UTF_8)).toString();
+                final String name = ess.getSettings().isSafeUsermap() ? StringUtil.safeString(config.getUsername()) : config.getUsername();
-                ess.getUserMap().removeUserUUID(uuid);
+                users.invalidate(UUID.nameUUIDFromBytes(("NPC:" + name).getBytes(Charsets.UTF_8)));
             }
         }
     }
@@ -88,14 +87,6 @@ public abstract class UserData extends PlayerExtension implements IConf {
             ess.getLogger().log(Level.SEVERE, "Error while reading user config: " + config.getFile().getName(), e);
             throw new RuntimeException(e);
         }
-        config.setSaveHook(() -> {
-            try {
-                config.getRootNode().set(UserConfigHolder.class, holder);
-            } catch (SerializationException e) {
-                ess.getLogger().log(Level.SEVERE, "Error while saving user config: " + config.getFile().getName(), e);
-                throw new RuntimeException(e);
-            }
-        });
         money = _getMoney();
     }
 
@@ -589,9 +580,13 @@ public abstract class UserData extends PlayerExtension implements IConf {
     }
 
     public void setLastAccountName(final String lastAccountName) {
+        if (getLastAccountName() != null && !getLastAccountName().equals(lastAccountName)) {
+            final List<String> usernames = holder.pastUsernames();
+            usernames.add(0, getLastAccountName());
+            holder.pastUsernames(usernames);
+        }
         holder.lastAccountName(lastAccountName);
         config.save();
-        ess.getUserMap().trackUUID(getConfigUUID(), lastAccountName, true);
     }
 
     public boolean arePowerToolsEnabled() {
@@ -722,6 +717,17 @@ public abstract class UserData extends PlayerExtension implements IConf {
         config.save();
     }
 
+    public List<String> getPastUsernames() {
+        return holder.pastUsernames();
+    }
+
+    public void addPastUsername(String username) {
+        final List<String> usernames = holder.pastUsernames();
+        usernames.add(0, username);
+        holder.pastUsernames(usernames);
+        config.save();
+    }
+
     public boolean isShouting() {
         if (holder.shouting() == null) {
             holder.shouting(ess.getSettings().isShoutDefault());

Essentials/src/main/java/com/earth2me/essentials/UserMap.java

@@ -1,383 +1,70 @@
 package com.earth2me.essentials;
 
 import com.earth2me.essentials.api.UserDoesNotExistException;
-import com.earth2me.essentials.utils.StringUtil;
+import com.earth2me.essentials.userstorage.ModernUserMap;
-import com.google.common.base.Charsets;
+import org.bukkit.Bukkit;
-import com.google.common.cache.Cache;
-import com.google.common.cache.CacheBuilder;
-import com.google.common.cache.CacheLoader;
-import com.google.common.cache.LoadingCache;
-import com.google.common.util.concurrent.UncheckedExecutionException;
-import net.ess3.api.IEssentials;
-import net.ess3.api.MaxMoneyException;
 import org.bukkit.entity.Player;
 
-import java.io.File;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import java.text.MessageFormat;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentSkipListMap;
-import java.util.concurrent.ConcurrentSkipListSet;
-import java.util.concurrent.ExecutionException;
-import java.util.logging.Level;
-import java.util.regex.Pattern;
 
-public class UserMap extends CacheLoader<String, User> implements IConf {
+@Deprecated
-    private static boolean legacy = false;
+public class UserMap {
-    private static Method getLegacy;
+    private final transient ModernUserMap userMap;
-    private final transient IEssentials ess;
+    private final transient UUIDMap uuidMap;
-    private final transient ConcurrentSkipListSet<UUID> keys = new ConcurrentSkipListSet<>();
-    private final transient ConcurrentSkipListMap<String, UUID> names = new ConcurrentSkipListMap<>();
-    private final transient ConcurrentSkipListMap<UUID, ArrayList<String>> history = new ConcurrentSkipListMap<>();
-    private final UUIDMap uuidMap;
-    private final transient Cache<String, User> users;
-    private final Pattern validUserPattern = Pattern.compile("^[a-zA-Z0-9_]{2,16}$");
 
-    private static final String WARN_UUID_NOT_REPLACE = "Found UUID {0} for player {1}, but player already has a UUID ({2}). Not replacing UUID in usermap.";
+    public UserMap(final ModernUserMap userMap) {
-
+        this.userMap = userMap;
-    public UserMap(final IEssentials ess) {
+        this.uuidMap = new UUIDMap();
-        super();
-        this.ess = ess;
-        uuidMap = new UUIDMap(ess);
-        //RemovalListener<UUID, User> remListener = new UserMapRemovalListener();
-        //users = CacheBuilder.newBuilder().maximumSize(ess.getSettings().getMaxUserCacheCount()).softValues().removalListener(remListener).build(this);
-        final CacheBuilder<Object, Object> cacheBuilder = CacheBuilder.newBuilder();
-        final int maxCount = ess.getSettings().getMaxUserCacheCount();
-        try {
-            cacheBuilder.maximumSize(maxCount);
-        } catch (final NoSuchMethodError nsme) {
-            legacy = true;
-            legacyMaximumSize(cacheBuilder, maxCount);
-        }
-        cacheBuilder.softValues();
-        if (!legacy) {
-            users = cacheBuilder.build(this);
-        } else {
-            users = legacyBuild(cacheBuilder);
-        }
-    }
-
-    private void loadAllUsersAsync(final IEssentials ess) {
-        ess.runTaskAsynchronously(() -> {
-            synchronized (users) {
-                final File userdir = new File(ess.getDataFolder(), "userdata");
-                if (!userdir.exists()) {
-                    return;
-                }
-                keys.clear();
-                users.invalidateAll();
-                for (final String string : userdir.list()) {
-                    if (!string.endsWith(".yml")) {
-                        continue;
-                    }
-                    final String name = string.substring(0, string.length() - 4);
-                    try {
-                        keys.add(UUID.fromString(name));
-                    } catch (final IllegalArgumentException ex) {
-                        //Ignore these users till they rejoin.
-                    }
-                }
-                uuidMap.loadAllUsers(names, history);
-            }
-        });
-    }
-
-    public boolean userExists(final UUID uuid) {
-        return keys.contains(uuid);
     }
 
     public User getUser(final String name) {
-        final String sanitizedName = StringUtil.safeString(name);
+        return userMap.getUser(name);
-        try {
-            if (ess.getSettings().isDebug()) {
-                ess.getLogger().warning("Looking up username " + name + " (" + sanitizedName + ") ...");
-            }
-
-            if (names.containsKey(sanitizedName)) {
-                final UUID uuid = names.get(sanitizedName);
-                return getUser(uuid);
-            }
-
-            if (ess.getSettings().isDebug()) {
-                ess.getLogger().warning(name + "(" + sanitizedName + ") has no known usermap entry");
-            }
-
-            final File userFile = getUserFileFromString(sanitizedName);
-            if (userFile.exists()) {
-                ess.getLogger().info("Importing user " + name + " to usermap.");
-                final User user = new User(new OfflinePlayer(sanitizedName, ess.getServer()), ess);
-                trackUUID(user.getBase().getUniqueId(), user.getName(), true);
-                return user;
-            }
-            return null;
-        } catch (final UncheckedExecutionException ex) {
-            if (ess.getSettings().isDebug()) {
-                ess.getLogger().log(Level.WARNING, ex, () -> String.format("Exception while getting user for %s (%s)", name, sanitizedName));
-            }
-            return null;
-        }
     }
 
     public User getUser(final UUID uuid) {
-        try {
+        return userMap.getUser(uuid);
-            if (!legacy) {
-                return ((LoadingCache<String, User>) users).get(uuid.toString());
-            } else {
-                return legacyCacheGet(uuid);
-            }
-        } catch (final ExecutionException | UncheckedExecutionException ex) {
-            if (ess.getSettings().isDebug()) {
-                ess.getLogger().log(Level.WARNING, ex, () -> "Exception while getting user for " + uuid);
-            }
-            return null;
-        }
     }
 
     public void trackUUID(final UUID uuid, final String name, final boolean replace) {
-        if (uuid != null) {
+        // no-op
-            keys.add(uuid);
-            if (name != null && name.length() > 0) {
-                final String keyName = ess.getSettings().isSafeUsermap() ? StringUtil.safeString(name) : name;
-                if (!names.containsKey(keyName)) {
-                    names.put(keyName, uuid);
-                    uuidMap.writeUUIDMap();
-                } else if (!isUUIDMatch(uuid, keyName)) {
-                    if (replace) {
-                        ess.getLogger().info("Found new UUID for " + name + ". Replacing " + names.get(keyName).toString() + " with " + uuid.toString());
-                        names.put(keyName, uuid);
-                        uuidMap.writeUUIDMap();
-                    } else {
-                        ess.getLogger().log(Level.INFO, MessageFormat.format(WARN_UUID_NOT_REPLACE, uuid.toString(), name, names.get(keyName).toString()), new RuntimeException());
-                    }
-                }
-            }
-        }
     }
 
-    public boolean isUUIDMatch(final UUID uuid, final String name) {
-        return names.containsKey(name) && names.get(name).equals(uuid);
-    }
-
-    @Override
     public User load(final String stringUUID) throws Exception {
-        final UUID uuid = UUID.fromString(stringUUID);
+        return userMap.load(UUID.fromString(stringUUID));
-        Player player = ess.getServer().getPlayer(uuid);
-        if (player != null) {
-            final User user = new User(player, ess);
-            trackUUID(uuid, user.getName(), true);
-            return user;
-        }
-
-        final File userFile = getUserFileFromID(uuid);
-
-        if (userFile.exists()) {
-            player = new OfflinePlayer(uuid, ess.getServer());
-            final User user = new User(player, ess);
-            ((OfflinePlayer) player).setName(user.getLastAccountName());
-            trackUUID(uuid, user.getName(), false);
-            return user;
-        }
-
-        throw new Exception("User not found!");
     }
 
     public User load(final org.bukkit.OfflinePlayer player) throws UserDoesNotExistException {
-        if (player == null) {
+        final Player userPlayer;
-            throw new IllegalArgumentException("Player cannot be null!");
-        }
-
         if (player instanceof Player) {
-            if (ess.getSettings().isDebug()) {
+            userPlayer = (Player) player;
-                ess.getLogger().info("Loading online OfflinePlayer into user map...");
-            }
-            final User user = new User((Player) player, ess);
-            trackUUID(player.getUniqueId(), player.getName(), true);
-            return user;
-        }
-
-        final File userFile = getUserFileFromID(player.getUniqueId());
-        if (ess.getSettings().isDebug()) {
-            ess.getLogger().info("Loading OfflinePlayer into user map. Has data: " + userFile.exists() + " for " + player);
-        }
-
-        final OfflinePlayer essPlayer = new OfflinePlayer(player.getUniqueId(), ess.getServer());
-        final User user = new User(essPlayer, ess);
-        if (userFile.exists()) {
-            essPlayer.setName(user.getLastAccountName());
         } else {
-            if (ess.getSettings().isDebug()) {
+            final com.earth2me.essentials.OfflinePlayer essPlayer = new com.earth2me.essentials.OfflinePlayer(player.getUniqueId(), Bukkit.getServer());
-                ess.getLogger().info("OfflinePlayer usermap load saving user data for " + player);
+            essPlayer.setName(player.getName());
+            userPlayer = essPlayer;
         }
 
-            // this code makes me sad
+        final User user = userMap.getUser(userPlayer);
-            user.startTransaction();
+        if (user == null) {
-            try {
+            throw new UserDoesNotExistException("User not found");
-                user.setMoney(ess.getSettings().getStartingBalance());
-            } catch (MaxMoneyException e) {
-                // Shouldn't happen as it would be an illegal configuration state
-                throw new RuntimeException(e);
         }
-            user.setLastAccountName(user.getName());
-            user.stopTransaction();
-        }
-
-        trackUUID(player.getUniqueId(), user.getName(), false);
         return user;
     }
 
-    @Override
-    public void reloadConfig() {
-        getUUIDMap().forceWriteUUIDMap();
-        loadAllUsersAsync(ess);
-    }
-
-    public void invalidateAll() {
-        users.invalidateAll();
-    }
-
-    public void removeUser(final String name) {
-        if (names == null) {
-            ess.getLogger().warning("Name collection is null, cannot remove user.");
-            return;
-        }
-        final UUID uuid = names.get(name);
-        if (uuid != null) {
-            keys.remove(uuid);
-            users.invalidate(uuid.toString());
-        }
-        names.remove(name);
-        names.remove(StringUtil.safeString(name));
-    }
-
-    public void removeUserUUID(final String uuid) {
-        users.invalidate(uuid);
-    }
-
     public Set<UUID> getAllUniqueUsers() {
-        return Collections.unmodifiableSet(keys);
+        return userMap.getAllUserUUIDs();
     }
 
     public int getUniqueUsers() {
-        return keys.size();
+        return userMap.getUserCount();
     }
 
     protected ConcurrentSkipListMap<String, UUID> getNames() {
-        return names;
+        return new ConcurrentSkipListMap<>(userMap.getNameCache());
-    }
-
-    protected ConcurrentSkipListMap<UUID, ArrayList<String>> getHistory() {
-        return history;
-    }
-
-    public List<String> getUserHistory(final UUID uuid) {
-        return history.get(uuid);
     }
 
     public UUIDMap getUUIDMap() {
         return uuidMap;
     }
-    //  class UserMapRemovalListener implements RemovalListener
-    //  {
-    //      @Override
-    //      public void onRemoval(final RemovalNotification notification)
-    //      {
-    //          Object value = notification.getValue();
-    //          if (value != null)
-    //          {
-    //              ((User)value).cleanup();
-    //          }
-    //      }
-    //  }
-
-    private File getUserFileFromID(final UUID uuid) {
-        final File userFolder = new File(ess.getDataFolder(), "userdata");
-        return new File(userFolder, uuid.toString() + ".yml");
-    }
-
-    public File getUserFileFromString(final String name) {
-        final File userFolder = new File(ess.getDataFolder(), "userdata");
-        return new File(userFolder, StringUtil.sanitizeFileName(name) + ".yml");
-    }
-
-    @SuppressWarnings("deprecation")
-    public User getUserFromBukkit(String name) {
-        name = StringUtil.safeString(name);
-        if (ess.getSettings().isDebug()) {
-            ess.getLogger().warning("Using potentially blocking Bukkit UUID lookup for: " + name);
-        }
-        // Don't attempt to look up entirely invalid usernames
-        if (name == null || !validUserPattern.matcher(name).matches()) {
-            return null;
-        }
-        final org.bukkit.OfflinePlayer offlinePlayer = ess.getServer().getOfflinePlayer(name);
-        if (offlinePlayer == null) {
-            return null;
-        }
-        final UUID uuid;
-        try {
-            uuid = offlinePlayer.getUniqueId();
-        } catch (final UnsupportedOperationException | NullPointerException e) {
-            return null;
-        }
-        // This is how Bukkit generates fake UUIDs
-        if (UUID.nameUUIDFromBytes(("OfflinePlayer:" + name).getBytes(Charsets.UTF_8)).equals(uuid)) {
-            return null;
-        } else {
-            names.put(name, uuid);
-            return getUser(uuid);
-        }
-    }
-
-    private User legacyCacheGet(final UUID uuid) {
-        if (getLegacy == null) {
-            final Class<?> usersClass = users.getClass();
-            for (final Method m : usersClass.getDeclaredMethods()) {
-                if (m.getName().equals("get")) {
-                    getLegacy = m;
-                    getLegacy.setAccessible(true);
-                    break;
-                }
-            }
-        }
-        try {
-            return (User) getLegacy.invoke(users, uuid.toString());
-        } catch (final IllegalAccessException | InvocationTargetException e) {
-            return null;
-        }
-    }
-
-    private void legacyMaximumSize(final CacheBuilder builder, final int maxCount) {
-        try {
-            final Method maxSizeLegacy = builder.getClass().getDeclaredMethod("maximumSize", Integer.TYPE);
-            maxSizeLegacy.setAccessible(true);
-            maxSizeLegacy.invoke(builder, maxCount);
-        } catch (final NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
-            e.printStackTrace();
-        }
-    }
-
-    @SuppressWarnings("unchecked")
-    private Cache<String, User> legacyBuild(final CacheBuilder builder) {
-        Method build = null;
-        for (final Method method : builder.getClass().getDeclaredMethods()) {
-            if (method.getName().equals("build")) {
-                build = method;
-                break;
-            }
-        }
-        Cache<String, User> legacyUsers;
-        try {
-            assert build != null;
-            build.setAccessible(true);
-            legacyUsers = (Cache<String, User>) build.invoke(builder, this);
-        } catch (final IllegalAccessException | InvocationTargetException e) {
-            legacyUsers = null;
-        }
-        return legacyUsers;
-    }
 }

Essentials/src/main/java/com/earth2me/essentials/api/Economy.java

@@ -3,6 +3,7 @@ package com.earth2me.essentials.api;
 import com.earth2me.essentials.Trade;
 import com.earth2me.essentials.User;
 import com.earth2me.essentials.config.EssentialsUserConfiguration;
+import com.earth2me.essentials.userstorage.ModernUserMap;
 import com.earth2me.essentials.utils.NumberUtil;
 import com.earth2me.essentials.utils.StringUtil;
 import com.google.common.base.Charsets;
@@ -41,9 +42,9 @@ public class Economy {
         ess = aEss;
     }
 
-    private static void createNPCFile(String name) {
+    private static void createNPCFile(final String unsanitizedName) {
         final File folder = new File(ess.getDataFolder(), "userdata");
-        name = StringUtil.safeString(name);
+        final String name = ess.getSettings().isSafeUsermap() ? StringUtil.safeString(unsanitizedName) : unsanitizedName;
         if (!folder.exists()) {
             if (!folder.mkdirs()) {
                 throw new RuntimeException("Error while creating userdata directory!");
@@ -59,9 +60,12 @@ public class Economy {
         npcConfig.load();
         npcConfig.setProperty("npc", true);
         npcConfig.setProperty("last-account-name", name);
+        npcConfig.setProperty("npc-name", unsanitizedName);
         npcConfig.setProperty("money", ess.getSettings().getStartingBalance());
         npcConfig.blockingSave();
-        ess.getUserMap().trackUUID(npcUUID, name, false);
+        // This will load the NPC into the UserMap + UUID cache
+        ((ModernUserMap) ess.getUsers()).addCachedNpcName(npcUUID, name);
+        ess.getUsers().getUser(npcUUID);
     }
 
     private static void deleteNPC(final String name) {

Essentials/src/main/java/com/earth2me/essentials/commands/Commandbalancetop.java

@@ -64,8 +64,8 @@ public class Commandbalancetop extends EssentialsCommand {
         }
 
         // If there are less than 50 users in our usermap, there is no need to display a warning as these calculations should be done quickly
-        if (ess.getUserMap().getUniqueUsers() > MINUSERS) {
+        if (ess.getUsers().getUserCount() > MINUSERS) {
-            sender.sendMessage(tl("orderBalances", ess.getUserMap().getUniqueUsers()));
+            sender.sendMessage(tl("orderBalances", ess.getUsers().getUserCount()));
         }
 
         ess.runTaskAsynchronously(new Viewer(sender, page, force));

Essentials/src/main/java/com/earth2me/essentials/commands/Commandessentials.java

@@ -3,9 +3,9 @@ package com.earth2me.essentials.commands;
 import com.earth2me.essentials.CommandSource;
 import com.earth2me.essentials.EssentialsUpgrade;
 import com.earth2me.essentials.User;
-import com.earth2me.essentials.UserMap;
 import com.earth2me.essentials.economy.EconomyLayer;
 import com.earth2me.essentials.economy.EconomyLayers;
+import com.earth2me.essentials.userstorage.ModernUserMap;
 import com.earth2me.essentials.utils.CommandMapUtil;
 import com.earth2me.essentials.utils.DateUtil;
 import com.earth2me.essentials.utils.EnumUtil;
@@ -13,7 +13,6 @@ import com.earth2me.essentials.utils.FloatUtil;
 import com.earth2me.essentials.utils.NumberUtil;
 import com.earth2me.essentials.utils.PasteUtil;
 import com.earth2me.essentials.utils.VersionUtil;
-import com.google.common.base.Charsets;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
 import com.google.gson.JsonArray;
@@ -33,6 +32,7 @@ import org.bukkit.plugin.PluginDescriptionFile;
 import org.bukkit.plugin.PluginManager;
 import org.bukkit.scheduler.BukkitRunnable;
 
+import java.io.File;
 import java.io.IOException;
 import java.lang.management.ManagementFactory;
 import java.nio.charset.StandardCharsets;
@@ -45,12 +45,15 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Supplier;
+import java.util.logging.Level;
 import java.util.stream.Collectors;
 
 import static com.earth2me.essentials.I18n.tl;
@@ -147,11 +150,8 @@ public class Commandessentials extends EssentialsCommand {
             case "homes":
                 runHomes(server, sender, commandLabel, args);
                 break;
-            case "uuidconvert":
+            case "usermap":
-                runUUIDConvert(server, sender, commandLabel, args);
+                runUserMap(sender, args);
-                break;
-            case "uuidtest":
-                runUUIDTest(server, sender, commandLabel, args);
                 break;
 
             // "#EasterEgg"
@@ -473,12 +473,11 @@ public class Commandessentials extends EssentialsCommand {
         final long daysArg = Long.parseLong(args[1]);
         final double moneyArg = args.length >= 3 ? FloatUtil.parseDouble(args[2].replaceAll("[^0-9\\.]", "")) : 0;
         final int homesArg = args.length >= 4 && NumberUtil.isInt(args[3]) ? Integer.parseInt(args[3]) : 0;
-        final UserMap userMap = ess.getUserMap();
 
         ess.runTaskAsynchronously(() -> {
             final long currTime = System.currentTimeMillis();
-            for (final UUID u : userMap.getAllUniqueUsers()) {
+            for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                final User user = ess.getUserMap().getUser(u);
+                final User user = ess.getUsers().loadUncachedUser(u);
                 if (user == null) {
                     continue;
                 }
@@ -523,13 +522,12 @@ public class Commandessentials extends EssentialsCommand {
             throw new Exception(HOMES_USAGE);
         }
 
-        final UserMap userMap = ess.getUserMap();
         switch (args[1]) {
             case "fix":
                 sender.sendMessage(tl("fixingHomes"));
                 ess.runTaskAsynchronously(() -> {
-                    for (final UUID u : userMap.getAllUniqueUsers()) {
+                    for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                        final User user = ess.getUserMap().getUser(u);
+                        final User user = ess.getUsers().loadUncachedUser(u);
                         if (user == null) {
                             continue;
                         }
@@ -553,8 +551,8 @@ public class Commandessentials extends EssentialsCommand {
                 }
                 sender.sendMessage(filterByWorld ? tl("deletingHomesWorld", args[2]) : tl("deletingHomes"));
                 ess.runTaskAsynchronously(() -> {
-                    for (final UUID u : userMap.getAllUniqueUsers()) {
+                    for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                        final User user = ess.getUserMap().getUser(u);
+                        final User user = ess.getUsers().loadUncachedUser(u);
                         if (user == null) {
                             continue;
                         }
@@ -577,52 +575,77 @@ public class Commandessentials extends EssentialsCommand {
         }
     }
 
-    // Forces a rerun of userdata UUID conversion.
+    // Gets information about cached users
-    private void runUUIDConvert(final Server server, final CommandSource sender, final String commandLabel, final String[] args) throws Exception {
+    private void runUserMap(final CommandSource sender, final String[] args) {
-        sender.sendMessage("Starting Essentials UUID userdata conversion; this may lag the server.");
+        if (!sender.isAuthorized("essentials.usermap", ess)) {
-
+            return;
-        final Boolean ignoreUFCache = args.length > 2 && args[1].toLowerCase(Locale.ENGLISH).contains("ignore");
-        EssentialsUpgrade.uuidFileConvert(ess, ignoreUFCache);
-
-        sender.sendMessage("UUID conversion complete. Check your server log for more information.");
         }
 
-    // Looks up various UUIDs for a user.
+        final ModernUserMap userMap = (ModernUserMap) ess.getUsers();
-    private void runUUIDTest(final Server server, final CommandSource sender, final String commandLabel, final String[] args) throws Exception {
+        sender.sendMessage(tl("usermapSize", userMap.getCachedCount(), userMap.getUserCount(), ess.getSettings().getMaxUserCacheCount()));
-        if (args.length < 2) {
+        if (args.length > 1) {
-            throw new Exception("/<command> uuidtest <name>");
+            if (args[1].equals("full")) {
+                for (final Map.Entry<String, UUID> entry : userMap.getNameCache().entrySet()) {
+                    sender.sendMessage(tl("usermapEntry", entry.getKey(), entry.getValue().toString()));
                 }
-        final String name = args[1];
+            } else if (args[1].equals("purge")) {
-        sender.sendMessage("Looking up UUID for " + name);
+                final boolean seppuku = args.length > 2 && args[2].equals("iknowwhatimdoing");
 
-        UUID onlineUUID = null;
+                sender.sendMessage(tl("usermapPurge", String.valueOf(seppuku)));
 
-        for (final Player player : ess.getOnlinePlayers()) {
+                final Set<UUID> uuids = new HashSet<>(ess.getUsers().getAllUserUUIDs());
-            if (player.getName().equalsIgnoreCase(name)) {
+                ess.runTaskAsynchronously(() -> {
-                onlineUUID = player.getUniqueId();
+                    final File userdataFolder = new File(ess.getDataFolder(), "userdata");
-                break;
+                    final File backupFolder = new File(ess.getDataFolder(), "userdata-npc-backup-boogaloo-" + System.currentTimeMillis());
-            }
+
+                    if (!userdataFolder.isDirectory()) {
+                        ess.getLogger().warning("Missing userdata folder, aborting usermap purge.");
+                        return;
                     }
 
-        final UUID essUUID = ess.getUserMap().getUser(name).getConfigUUID();
+                    if (seppuku && !backupFolder.mkdir()) {
-
+                        ess.getLogger().warning("Unable to create backup folder, aborting usermap purge.");
-        final org.bukkit.OfflinePlayer player = ess.getServer().getOfflinePlayer(name);
+                        return;
-        final UUID bukkituuid = player.getUniqueId();
-        sender.sendMessage("Bukkit Lookup: " + bukkituuid.toString());
-
-        if (onlineUUID != null && onlineUUID != bukkituuid) {
-            sender.sendMessage("Online player: " + onlineUUID.toString());
                     }
 
-        if (essUUID != null && essUUID != bukkituuid) {
+                    int total = 0;
-            sender.sendMessage("Essentials config: " + essUUID.toString());
+                    final File[] files = userdataFolder.listFiles(EssentialsUpgrade.YML_FILTER);
+                    if (files != null) {
+                        for (final File file : files) {
+                            try {
+                                final String fileName = file.getName();
+                                final UUID uuid = UUID.fromString(fileName.substring(0, fileName.length() - 4));
+                                if (!uuids.contains(uuid)) {
+                                    total++;
+                                    ess.getLogger().warning("Found orphaned userdata file: " + file.getName());
+                                    if (seppuku) {
+                                        try {
+                                            com.google.common.io.Files.move(file, new File(backupFolder, file.getName()));
+                                        } catch (IOException e) {
+                                            ess.getLogger().log(Level.WARNING, "Unable to move orphaned userdata file: " + file.getName(), e);
+                                        }
+                                    }
+                                }
+                            } catch (IllegalArgumentException ignored) {
+                            }
+                        }
+                    }
+                    ess.getLogger().info("Found " + total + " orphaned userdata files.");
+                });
+            } else {
+                try {
+                    final UUID uuid = UUID.fromString(args[1]);
+                    for (final Map.Entry<String, UUID> entry : userMap.getNameCache().entrySet()) {
+                        if (entry.getValue().equals(uuid)) {
+                            sender.sendMessage(tl("usermapEntry", entry.getKey(), args[1]));
+                        }
+                    }
+                } catch (IllegalArgumentException ignored) {
+                    final String sanitizedName = userMap.getSanitizedName(args[1]);
+                    sender.sendMessage(tl("usermapEntry", sanitizedName, userMap.getNameCache().get(sanitizedName).toString()));
+                }
+            }
         }
-
-        final UUID npcuuid = UUID.nameUUIDFromBytes(("NPC:" + name).getBytes(Charsets.UTF_8));
-        sender.sendMessage("NPC UUID: " + npcuuid.toString());
-
-        final UUID offlineuuid = UUID.nameUUIDFromBytes(("OfflinePlayer:" + name).getBytes(Charsets.UTF_8));
-        sender.sendMessage("Offline Mode UUID: " + offlineuuid.toString());
     }
 
     // Displays versions of EssentialsX and related plugins.
@@ -750,7 +773,6 @@ public class Commandessentials extends EssentialsCommand {
             options.add("cleanup");
             options.add("homes");
             //options.add("uuidconvert");
-            //options.add("uuidtest");
             //options.add("nya");
             //options.add("moo");
             return options;
@@ -763,7 +785,6 @@ public class Commandessentials extends EssentialsCommand {
                 }
                 break;
             case "reset":
-            case "uuidtest":
                 if (args.length == 2) {
                     return getPlayers(server, sender);
                 }
@@ -782,11 +803,6 @@ public class Commandessentials extends EssentialsCommand {
                     return server.getWorlds().stream().map(World::getName).collect(Collectors.toList());
                 }
                 break;
-            case "uuidconvert":
-                if (args.length == 2) {
-                    return Lists.newArrayList("ignoreUFCache");
-                }
-                break;
             case "dump":
                 final List<String> list = Lists.newArrayList("config", "kits", "log", "discord", "worth", "tpr", "spawns", "commands", "all");
                 for (String arg : args) {

Essentials/src/main/java/com/earth2me/essentials/commands/Commandmail.java

@@ -261,8 +261,8 @@ public class Commandmail extends EssentialsCommand {
 
         @Override
         public void run() {
-            for (UUID userid : ess.getUserMap().getAllUniqueUsers()) {
+            for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                final User user = ess.getUserMap().getUser(userid);
+                final User user = ess.getUsers().loadUncachedUser(u);
                 if (user != null) {
                     user.sendMail(messageRecipient, message, dateDiff);
                 }

Essentials/src/main/java/com/earth2me/essentials/commands/Commandseen.java

@@ -2,7 +2,6 @@ package com.earth2me.essentials.commands;
 
 import com.earth2me.essentials.CommandSource;
 import com.earth2me.essentials.User;
-import com.earth2me.essentials.UserMap;
 import com.earth2me.essentials.craftbukkit.BanLookup;
 import com.earth2me.essentials.utils.DateUtil;
 import com.earth2me.essentials.utils.FormatUtil;
@@ -63,7 +62,7 @@ public class Commandseen extends EssentialsCommand {
             ess.getScheduler().runTaskAsynchronously(ess, new Runnable() {
                 @Override
                 public void run() {
-                    final User userFromBukkit = ess.getUserMap().getUserFromBukkit(args[0]);
+                    final User userFromBukkit = ess.getUsers().getUser(args[0]);
                     try {
                         if (userFromBukkit != null) {
                             showUserSeen(userFromBukkit);
@@ -103,8 +102,8 @@ public class Commandseen extends EssentialsCommand {
         user.setDisplayNick();
         sender.sendMessage(tl("seenOnline", user.getDisplayName(), DateUtil.formatDateDiff(user.getLastLogin())));
 
-        final List<String> history = ess.getUserMap().getUserHistory(user.getBase().getUniqueId());
+        final List<String> history = user.getPastUsernames();
-        if (history != null && history.size() > 1) {
+        if (history != null && !history.isEmpty()) {
             sender.sendMessage(tl("seenAccounts", StringUtil.joinListSkip(", ", user.getName(), history)));
         }
 
@@ -139,7 +138,7 @@ public class Commandseen extends EssentialsCommand {
         user.setDisplayNick();
         if (user.getLastLogout() > 0) {
             sender.sendMessage(tl("seenOffline", user.getName(), DateUtil.formatDateDiff(user.getLastLogout())));
-            final List<String> history = ess.getUserMap().getUserHistory(user.getBase().getUniqueId());
+            final List<String> history = user.getPastUsernames();
             if (history != null && history.size() > 1) {
                 sender.sendMessage(tl("seenAccounts", StringUtil.joinListSkip(", ", user.getName(), history)));
             }
@@ -192,14 +191,12 @@ public class Commandseen extends EssentialsCommand {
     }
 
     private void seenIP(final CommandSource sender, final String ipAddress, final String display) {
-        final UserMap userMap = ess.getUserMap();
-
         sender.sendMessage(tl("runningPlayerMatch", display));
 
         ess.runTaskAsynchronously(() -> {
             final List<String> matches = new ArrayList<>();
-            for (final UUID u : userMap.getAllUniqueUsers()) {
+            for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                final User user = ess.getUserMap().getUser(u);
+                final User user = ess.getUsers().loadUncachedUser(u);
                 if (user == null) {
                     continue;
                 }

Essentials/src/main/java/com/earth2me/essentials/commands/EssentialsLoopCommand.java

@@ -32,9 +32,9 @@ public abstract class EssentialsLoopCommand extends EssentialsCommand {
             final User matchedUser = ess.getUser(uuid);
             userConsumer.accept(matchedUser);
         } else if (matchWildcards && searchTerm.contentEquals("**")) {
-            for (final UUID sUser : ess.getUserMap().getAllUniqueUsers()) {
+            for (final UUID u : ess.getUsers().getAllUserUUIDs()) {
-                final User matchedUser = ess.getUser(sUser);
+                final User user = ess.getUsers().loadUncachedUser(u);
-                userConsumer.accept(matchedUser);
+                userConsumer.accept(user);
             }
         } else if (matchWildcards && searchTerm.contentEquals("*")) {
             final boolean skipHidden = sender.isPlayer() && !ess.getUser(sender.getPlayer()).canInteractVanished();

Essentials/src/main/java/com/earth2me/essentials/config/EssentialsConfiguration.java

@@ -103,6 +103,15 @@ public class EssentialsConfiguration {
         return configurationNode;
     }
 
+    public void setRootHolder(final Class<?> holderClass, final Object holder) {
+        try {
+            getRootNode().set(holderClass, holder);
+        } catch (SerializationException e) {
+            Essentials.getWrappedLogger().log(Level.SEVERE, "Error while saving user config: " + configFile.getName(), e);
+            throw new RuntimeException(e);
+        }
+    }
+
     public File getFile() {
         return configFile;
     }
@@ -366,10 +375,10 @@ public class EssentialsConfiguration {
         } catch (final ParsingException e) {
             final File broken = new File(configFile.getAbsolutePath() + ".broken." + System.currentTimeMillis());
             if (configFile.renameTo(broken)) {
-                Essentials.getWrappedLogger().log(Level.SEVERE, "The file " + configFile.toString() + " is broken, it has been renamed to " + broken.toString(), e.getCause());
+                Essentials.getWrappedLogger().log(Level.SEVERE, "The file " + configFile + " is broken, it has been renamed to " + broken, e.getCause());
                 return;
             }
-            Essentials.getWrappedLogger().log(Level.SEVERE, "The file " + configFile.toString() + " is broken. A backup file has failed to be created", e.getCause());
+            Essentials.getWrappedLogger().log(Level.SEVERE, "The file " + configFile + " is broken. A backup file has failed to be created", e.getCause());
         } catch (final ConfigurateException e) {
             Essentials.getWrappedLogger().log(Level.SEVERE, e.getMessage(), e);
         } finally {
@@ -420,6 +429,10 @@ public class EssentialsConfiguration {
         }
     }
 
+    public boolean isTransaction() {
+        return transaction.get();
+    }
+
     public void setSaveHook(Runnable saveHook) {
         this.saveHook = saveHook;
     }

Essentials/src/main/java/com/earth2me/essentials/config/EssentialsUserConfiguration.java

@@ -52,7 +52,7 @@ public class EssentialsUserConfiguration extends EssentialsConfiguration {
 
     private File getAltFile() {
         final UUID fn = UUID.nameUUIDFromBytes(("OfflinePlayer:" + username.toLowerCase(Locale.ENGLISH)).getBytes(Charsets.UTF_8));
-        return new File(configFile.getParentFile(), fn.toString() + ".yml");
+        return new File(configFile.getParentFile(), fn + ".yml");
     }
 
     @Override

Essentials/src/main/java/com/earth2me/essentials/config/holders/UserConfigHolder.java

@@ -262,6 +262,16 @@ public class UserConfigHolder {
         this.lastAccountName = value;
     }
 
+    private @MonotonicNonNull String npcName;
+
+    public String npcName() {
+        return this.npcName;
+    }
+
+    public void npcName(final String value) {
+        this.npcName = value;
+    }
+
     private boolean powertoolsenabled = true;
 
     public boolean powerToolsEnabled() {
@@ -332,6 +342,20 @@ public class UserConfigHolder {
         this.shouting = value;
     }
 
+    @DeleteOnEmpty
+    private @MonotonicNonNull List<String> pastUsernames;
+
+    public List<String> pastUsernames() {
+        if (this.pastUsernames == null) {
+            this.pastUsernames = new ArrayList<>();
+        }
+        return this.pastUsernames;
+    }
+
+    public void pastUsernames(List<String> value) {
+        this.pastUsernames = value;
+    }
+
     private @NonNull Timestamps timestamps = new Timestamps();
 
     public Timestamps timestamps() {

Essentials/src/main/java/com/earth2me/essentials/economy/vault/VaultEconomyProvider.java

@@ -11,6 +11,7 @@ import net.ess3.api.MaxMoneyException;
 import net.milkbowl.vault.economy.Economy;
 import net.milkbowl.vault.economy.EconomyResponse;
 import org.bukkit.OfflinePlayer;
+import org.bukkit.entity.Player;
 
 import java.io.File;
 import java.math.BigDecimal;
@@ -308,21 +309,27 @@ public class VaultEconomyProvider implements Economy {
             npcConfig.setProperty("last-account-name", player.getName());
             npcConfig.setProperty("money", ess.getSettings().getStartingBalance());
             npcConfig.blockingSave();
-            ess.getUserMap().trackUUID(player.getUniqueId(), player.getName(), false);
+            // This will load the NPC into the UserMap + UUID cache
+            ess.getUsers().addCachedNpcName(player.getUniqueId(), player.getName());
+            ess.getUsers().getUser(player.getUniqueId());
             return true;
         }
 
         // Loading a v4 UUID that we somehow didn't track, mark it as a normal player and hope for the best, vault sucks :/
-        try {
         if (ess.getSettings().isDebug()) {
             ess.getLogger().info("Vault requested a player account creation for a v4 UUID: " + player);
         }
-            ess.getUserMap().load(player);
+
-            return true;
+        final Player userPlayer;
-        } catch (UserDoesNotExistException e) {
+        if (player instanceof Player) {
-            e.printStackTrace();
+            userPlayer = (Player) player;
-            return false;
+        } else {
+            final com.earth2me.essentials.OfflinePlayer essPlayer = new com.earth2me.essentials.OfflinePlayer(player.getUniqueId(), ess.getServer());
+            essPlayer.setName(player.getName());
+            userPlayer = essPlayer;
         }
+        ess.getUsers().getUser(userPlayer);
+        return true;
     }
 
     @Override

Essentials/src/main/java/com/earth2me/essentials/perm/impl/LuckPermsHandler.java

@@ -70,11 +70,11 @@ public class LuckPermsHandler extends ModernVaultHandler {
             // If the player doesn't exist in the UserMap, just skip
             // Ess will cause performance problems for permissions checks if it attempts to
             // perform i/o to load the user data otherwise.
-            if (!ess.getUserMap().userExists(target.getUniqueId())) {
+            if (!ess.getUsers().getAllUserUUIDs().contains(target.getUniqueId())) {
                 return;
             }
 
-            final User user = ess.getUser(target);
+            final User user = ess.getUsers().loadUncachedUser(target.getUniqueId());
             for (Calculator calculator : this.calculators) {
                 calculator.function.apply(user).forEach(value -> consumer.accept(calculator.id, value));
             }

Essentials/src/main/java/com/earth2me/essentials/textreader/KeywordReplacer.java

@@ -253,7 +253,7 @@ public class KeywordReplacer implements IText {
                         replacer = Integer.toString(ess.getOnlinePlayers().size() - playerHidden);
                         break;
                     case UNIQUE:
-                        replacer = NumberFormat.getInstance().format(ess.getUserMap().getUniqueUsers());
+                        replacer = NumberFormat.getInstance().format(ess.getUsers().getUserCount());
                         break;
                     case WORLDS:
                         final StringBuilder worldsBuilder = new StringBuilder();

Essentials/src/main/java/com/earth2me/essentials/userstorage/IUserMap.java

@@ -0,0 +1,51 @@
+package com.earth2me.essentials.userstorage;
+
+import com.earth2me.essentials.User;
+import org.bukkit.entity.Player;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+public interface IUserMap {
+    /**
+     * Gets all the UUIDs of every User which has joined.
+     * @return the UUIDs of all Users.
+     */
+    Set<UUID> getAllUserUUIDs();
+
+    /**
+     * Gets the current amount of users loaded into memory.
+     * @return the amount of users loaded into memory.
+     */
+    long getCachedCount();
+
+    /**
+     * Gets the amount of users stored by Essentials.
+     * @return the amount of users stored by Essentials.
+     */
+    int getUserCount();
+
+    User getUser(final UUID uuid);
+
+    User getUser(final Player base);
+
+    User getUser(final String name);
+
+    User loadUncachedUser(final Player base);
+
+    /**
+     * Gets a User by the given UUID in the cache, if present, otherwise loads the user without placing them in the cache.
+     * Ideally to be used when running operations on all stored users.
+     *
+     * @param uuid the UUID of the user to get.
+     * @return the User with the given UUID, or null if not found.
+     */
+    User loadUncachedUser(final UUID uuid);
+
+    /**
+     * Gets the name to UUID cache.
+     * @return the name to UUID cache.
+     */
+    Map<String, UUID> getNameCache();
+}

Essentials/src/main/java/com/earth2me/essentials/userstorage/ModernUUIDCache.java

@@ -0,0 +1,250 @@
+package com.earth2me.essentials.userstorage;
+
+import com.earth2me.essentials.utils.StringUtil;
+import com.google.common.io.Files;
+import net.ess3.api.IEssentials;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Level;
+
+public class ModernUUIDCache {
+    private final IEssentials ess;
+
+    /**
+     * We use a name to uuid map for offline caching due to the following scenario:
+     * * JRoy and mdcfeYT420 play on a server
+     * * mdcfeYT420 changes his name to mdcfe
+     * * mdcfe doesn't log in the server for 31 days
+     * * JRoy changes his name to mdcfeYT420
+     * * mdcfeYT420 (previously JRoy) logs in the server
+     * In a UUID->Name based map, different uuids now point to the same name
+     * preventing any command which allows for offline players from resolving a
+     * given uuid from a given name.
+     * <p>
+     * This map is backed by a file-based cache. If this cache is missing, a new
+     * one is populated by iterating over all files in the userdata folder and
+     * caching the {@code last-account-name} value.
+     */
+    private final ConcurrentHashMap<String, UUID> nameToUuidMap = new ConcurrentHashMap<>();
+    private final CopyOnWriteArraySet<UUID> uuidCache = new CopyOnWriteArraySet<>();
+
+    private final ScheduledExecutorService writeExecutor = Executors.newSingleThreadScheduledExecutor();
+    private final AtomicBoolean pendingNameWrite = new AtomicBoolean(false);
+    private final AtomicBoolean pendingUuidWrite = new AtomicBoolean(false);
+    private final File nameToUuidFile;
+    private final File uuidCacheFile;
+
+    public ModernUUIDCache(final IEssentials ess) {
+        this.ess = ess;
+        this.nameToUuidFile = new File(ess.getDataFolder(), "usermap.bin");
+        this.uuidCacheFile = new File(ess.getDataFolder(), "uuids.bin");
+        loadCache();
+        writeExecutor.scheduleWithFixedDelay(() -> {
+            if (pendingNameWrite.compareAndSet(true, false)) {
+                saveNameToUuidCache();
+            }
+
+            if (pendingUuidWrite.compareAndSet(true, false)) {
+                saveUuidCache();
+            }
+        }, 5, 5, TimeUnit.SECONDS);
+    }
+
+    protected UUID getCachedUUID(final String name) {
+        return nameToUuidMap.get(getSanitizedName(name));
+    }
+
+    protected Set<UUID> getCachedUUIDs() {
+        return Collections.unmodifiableSet(uuidCache);
+    }
+
+    protected Map<String, UUID> getNameCache() {
+        return Collections.unmodifiableMap(nameToUuidMap);
+    }
+
+    protected int getCacheSize() {
+        return uuidCache.size();
+    }
+
+    protected String getSanitizedName(final String name) {
+        return ess.getSettings().isSafeUsermap() ? StringUtil.safeString(name) : name;
+    }
+
+    protected void updateCache(final UUID uuid, final String name) {
+        if (uuidCache.add(uuid)) {
+            pendingUuidWrite.set(true);
+        }
+        if (name != null) {
+            final String sanitizedName = getSanitizedName(name);
+            final UUID replacedUuid = nameToUuidMap.put(sanitizedName, uuid);
+            if (!uuid.equals(replacedUuid)) {
+                if (ess.getSettings().isDebug()) {
+                    ess.getLogger().log(Level.WARNING, "Replaced UUID during cache update for " + sanitizedName + ": " + replacedUuid + " -> " + uuid);
+                }
+                pendingNameWrite.set(true);
+            }
+        }
+    }
+
+    protected void removeCache(final UUID uuid) {
+        if (uuid == null) {
+            return;
+        }
+
+        if (uuidCache.remove(uuid)) {
+            pendingUuidWrite.set(true);
+        }
+
+        final Set<String> toRemove = new HashSet<>();
+        for (final Map.Entry<String, UUID> entry : nameToUuidMap.entrySet()) {
+            if (uuid.equals(entry.getValue())) {
+                toRemove.add(entry.getKey());
+            }
+        }
+
+        for (final String name : toRemove) {
+            nameToUuidMap.remove(name);
+        }
+
+        if (!toRemove.isEmpty()) {
+            pendingNameWrite.set(true);
+        }
+    }
+
+    private void loadCache() {
+        final boolean debug = ess.getSettings().isDebug();
+
+        try {
+            if (!nameToUuidFile.exists()) {
+                if (!nameToUuidFile.createNewFile()) {
+                    throw new RuntimeException("Error while creating usermap.bin");
+                }
+                return;
+            }
+
+            if (debug) {
+                ess.getLogger().log(Level.INFO, "Loading Name->UUID cache from disk...");
+            }
+
+            nameToUuidMap.clear();
+
+            try (final DataInputStream dis = new DataInputStream(new FileInputStream(nameToUuidFile))) {
+                while (dis.available() > 0) {
+                    final String username = dis.readUTF();
+                    final UUID uuid = new UUID(dis.readLong(), dis.readLong());
+                    final UUID previous = nameToUuidMap.put(username, uuid);
+                    if (previous != null && debug) {
+                        ess.getLogger().log(Level.WARNING, "Replaced UUID during cache load for " + username + ": " + previous + " -> " + uuid);
+                    }
+                }
+            }
+        } catch (IOException e) {
+            ess.getLogger().log(Level.SEVERE, "Error while loading Name->UUID cache", e);
+        }
+
+        try {
+            if (!uuidCacheFile.exists()) {
+                if (!uuidCacheFile.createNewFile()) {
+                    throw new RuntimeException("Error while creating uuids.bin");
+                }
+                return;
+            }
+
+            if (debug) {
+                ess.getLogger().log(Level.INFO, "Loading UUID cache from disk...");
+            }
+
+            uuidCache.clear();
+
+            try (final DataInputStream dis = new DataInputStream(new FileInputStream(uuidCacheFile))) {
+                while (dis.available() > 0) {
+                    final UUID uuid = new UUID(dis.readLong(), dis.readLong());
+                    if (uuidCache.contains(uuid) && debug) {
+                        ess.getLogger().log(Level.WARNING, "UUID " + uuid + " duplicated in cache");
+                    }
+                    uuidCache.add(uuid);
+                }
+            }
+        } catch (IOException e) {
+            ess.getLogger().log(Level.SEVERE, "Error while loading UUID cache", e);
+        }
+    }
+
+    private void saveUuidCache() {
+        if (ess.getSettings().isDebug()) {
+            ess.getLogger().log(Level.INFO, "Saving UUID cache to disk...");
+        }
+
+        try {
+            final File tmpMap = File.createTempFile("uuids", ".tmp.bin", ess.getDataFolder());
+
+            writeUuidCache(tmpMap, uuidCache);
+            //noinspection UnstableApiUsage
+            Files.move(tmpMap, uuidCacheFile);
+        } catch (IOException e) {
+            ess.getLogger().log(Level.SEVERE, "Error while saving UUID cache", e);
+        }
+    }
+
+    private void saveNameToUuidCache() {
+        if (ess.getSettings().isDebug()) {
+            ess.getLogger().log(Level.INFO, "Saving Name->UUID cache to disk...");
+        }
+
+        try {
+            final File tmpMap = File.createTempFile("usermap", ".tmp.bin", ess.getDataFolder());
+
+            writeNameUuidMap(tmpMap, nameToUuidMap);
+            //noinspection UnstableApiUsage
+            Files.move(tmpMap, nameToUuidFile);
+        } catch (IOException e) {
+            ess.getLogger().log(Level.SEVERE, "Error while saving Name->UUID cache", e);
+        }
+    }
+
+    protected void blockingSave() {
+        saveUuidCache();
+        saveNameToUuidCache();
+    }
+
+    public static void writeUuidCache(final File file, Set<UUID> uuids) throws IOException {
+        try (final DataOutputStream dos = new DataOutputStream(new FileOutputStream(file))) {
+            for (final UUID uuid: uuids) {
+                dos.writeLong(uuid.getMostSignificantBits());
+                dos.writeLong(uuid.getLeastSignificantBits());
+            }
+        }
+    }
+
+    public static void writeNameUuidMap(final File file, final Map<String, UUID> nameToUuidMap) throws IOException {
+        try (final DataOutputStream dos = new DataOutputStream(new FileOutputStream(file))) {
+            for (final Map.Entry<String, UUID> entry : nameToUuidMap.entrySet()) {
+                dos.writeUTF(entry.getKey());
+                final UUID uuid = entry.getValue();
+                dos.writeLong(uuid.getMostSignificantBits());
+                dos.writeLong(uuid.getLeastSignificantBits());
+            }
+        }
+    }
+
+    public void shutdown() {
+        writeExecutor.shutdownNow();
+        blockingSave();
+    }
+}

Essentials/src/main/java/com/earth2me/essentials/userstorage/ModernUserMap.java

@@ -0,0 +1,177 @@
+package com.earth2me.essentials.userstorage;
+
+import com.earth2me.essentials.OfflinePlayer;
+import com.earth2me.essentials.User;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import net.ess3.api.IEssentials;
+import org.bukkit.entity.Player;
+
+import java.io.File;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ExecutionException;
+import java.util.logging.Level;
+
+public class ModernUserMap extends CacheLoader<UUID, User> implements IUserMap {
+    private final transient IEssentials ess;
+    private final transient ModernUUIDCache uuidCache;
+    private final transient LoadingCache<UUID, User> userCache;
+
+    public ModernUserMap(final IEssentials ess) {
+        this.ess = ess;
+        this.uuidCache = new ModernUUIDCache(ess);
+        this.userCache = CacheBuilder.newBuilder()
+                .maximumSize(ess.getSettings().getMaxUserCacheCount())
+                .softValues()
+                .build(this);
+    }
+
+    @Override
+    public Set<UUID> getAllUserUUIDs() {
+        return uuidCache.getCachedUUIDs();
+    }
+
+    @Override
+    public long getCachedCount() {
+        return userCache.size();
+    }
+
+    @Override
+    public int getUserCount() {
+        return uuidCache.getCacheSize();
+    }
+
+    @Override
+    public User getUser(final UUID uuid) {
+        if (uuid == null) {
+            return null;
+        }
+
+        try {
+            return userCache.get(uuid);
+        } catch (ExecutionException e) {
+            if (ess.getSettings().isDebug()) {
+                ess.getLogger().log(Level.WARNING, "Exception while getting user for " + uuid, e);
+            }
+            return null;
+        }
+    }
+
+    @Override
+    public User getUser(final Player base) {
+        final User user = loadUncachedUser(base);
+        userCache.put(user.getUUID(), user);
+        return user;
+    }
+
+    @Override
+    public User getUser(final String name) {
+        if (name == null) {
+            return null;
+        }
+
+        final User user = getUser(uuidCache.getCachedUUID(name));
+        if (user != null && user.getBase() instanceof OfflinePlayer) {
+            if (user.getLastAccountName() != null) {
+                ((OfflinePlayer) user.getBase()).setName(user.getLastAccountName());
+            } else {
+                ((OfflinePlayer) user.getBase()).setName(name);
+            }
+        }
+        return user;
+    }
+
+    public void addCachedNpcName(final UUID uuid, final String name) {
+        if (uuid == null || name == null) {
+            return;
+        }
+
+        uuidCache.updateCache(uuid, name);
+    }
+
+    @SuppressWarnings("NullableProblems")
+    @Override
+    public User load(final UUID uuid) throws Exception {
+        final User user = loadUncachedUser(uuid);
+        if (user != null) {
+            return user;
+        }
+
+        throw new Exception("User not found!");
+    }
+
+    @Override
+    public User loadUncachedUser(final Player base) {
+        if (base == null) {
+            return null;
+        }
+
+        User user = getUser(base.getUniqueId());
+        if (user == null) {
+            ess.getLogger().log(Level.INFO, "Essentials created a User for " + base.getName() + " (" + base.getUniqueId() + ") for non Bukkit type: " + base.getClass().getName());
+            user = new User(base, ess);
+        } else if (!base.equals(user.getBase())) {
+            ess.getLogger().log(Level.INFO, "Essentials updated the underlying Player object for " + user.getUUID());
+            user.update(base);
+        }
+        uuidCache.updateCache(user.getUUID(), user.getName());
+
+        return user;
+    }
+
+    @Override
+    public User loadUncachedUser(final UUID uuid) {
+        User user = userCache.getIfPresent(uuid);
+        if (user != null) {
+            return user;
+        }
+
+        Player player = ess.getServer().getPlayer(uuid);
+        if (player != null) {
+            // This is a real player, cache their UUID.
+            user = new User(player, ess);
+            uuidCache.updateCache(uuid, player.getName());
+            return user;
+        }
+
+        final File userFile = getUserFile(uuid);
+        if (userFile.exists()) {
+            player = new OfflinePlayer(uuid, ess.getServer());
+            user = new User(player, ess);
+            ((OfflinePlayer) player).setName(user.getLastAccountName());
+            uuidCache.updateCache(uuid, null);
+            return user;
+        }
+
+        return null;
+    }
+
+    @Override
+    public Map<String, UUID> getNameCache() {
+        return uuidCache.getNameCache();
+    }
+
+    public String getSanitizedName(final String name) {
+        return uuidCache.getSanitizedName(name);
+    }
+
+    public void blockingSave() {
+        uuidCache.blockingSave();
+    }
+
+    public void invalidate(final UUID uuid) {
+        userCache.invalidate(uuid);
+        uuidCache.removeCache(uuid);
+    }
+
+    private File getUserFile(final UUID uuid) {
+        return new File(new File(ess.getDataFolder(), "userdata"), uuid.toString() + ".yml");
+    }
+
+    public void shutdown() {
+        uuidCache.shutdown();
+    }
+}

Essentials/src/main/java/com/earth2me/essentials/utils/StringUtil.java

@@ -25,6 +25,9 @@ public final class StringUtil {
 
     //Used to clean strings/names before saving as filenames/permissions
     public static String safeString(final String string) {
+        if (string == null) {
+            return null;
+        }
         return STRICTINVALIDCHARS.matcher(string.toLowerCase(Locale.ENGLISH)).replaceAll("_");
     }
 

Essentials/src/main/resources/messages.properties

@@ -1415,6 +1415,9 @@ userIsAwaySelf=\u00a77You are now AFK.
 userIsAwaySelfWithMessage=\u00a77You are now AFK.
 userIsNotAwaySelf=\u00a77You are no longer AFK.
 userJailed=\u00a76You have been jailed\!
+usermapEntry=\u00a7c{0} \u00a76is mapped to \u00a7c{1}\u00a76.
+usermapPurge=\u00a76Checking for files in userdata that are not mapped, results will be logged to console. Destructive Mode: {0}
+usermapSize=\u00a76Current cached users in user map is \u00a7c{0}\u00a76/\u00a7c{1}\u00a76/\u00a7c{2}\u00a76.
 userUnknown=\u00a74Warning\: The user ''\u00a7c{0}\u00a74'' has never joined this server.
 usingTempFolderForTesting=Using temp folder for testing\:
 vanish=\u00a76Vanish for {0}\u00a76\: {1}

EssentialsDiscord/src/main/java/net/essentialsx/discord/listeners/BukkitListener.java

@@ -137,7 +137,7 @@ public class BukkitListener implements Listener {
                         MessageUtil.sanitizeDiscordMarkdown(player.getDisplayName()),
                         MessageUtil.sanitizeDiscordMarkdown(message),
                         jda.getPlugin().getEss().getOnlinePlayers().size() - (join ? 0 : 1),
-                        jda.getPlugin().getEss().getUserMap().getUniqueUsers()),
+                        jda.getPlugin().getEss().getUsers().getUserCount()),
                         player);
     }
 

providers/1_12Provider/src/main/java/com/earth2me/essentials/OfflinePlayer.java

@@ -1341,7 +1341,7 @@ public class OfflinePlayer implements Player {
         return name;
     }
 
-    protected void setName(final String name) {
+    public void setName(final String name) {
         this.name = base.getName();
         if (this.name == null) {
             this.name = name;