feature: configurable CoW incremental backup

13 files changed, 261 insertions, 28 deletions

diff --git a/README.md b/README.md
index f39fc12..e3a95e5 100644
--- a/README.md
+++ b/README.md
@@ -57,26 +57,44 @@ Supported Minecraft version: 1.14.4, 1.15.2, 1.16.4/1.16.5, 1.17.1, 1.18.1
 - **/kb delete**: delete an existing backup.
 - **/kb prev**: Find and select the most recent backup file. After executing this command, you can use `/kb restore 1`
   to restore to this backup.
+- **/kb cow-info**: Check if copy-on-write backup is activated.
 
 Only OPs can make backups and restore by default.
 
 However, you can use permission management mods like [LuckPerms](https://luckperms.net/) to configure exactly what
 permissions normal players can use. Permission nodes of each command are listed below:
 
-| Command    | Permission Required |
-|------------|---------------------|
-| /kb        | kb.root             |
-| /kb help   | kb.help             |
-| /kb list   | kb.list             |
-| /kb backup | kb.backup           |
-| /kb incbak | kb.incbak           |
+| Command     | Permission Required |
+|-------------|---------------------|
+| /kb         | kb.root             |
+| /kb help    | kb.help             |
+| /kb list    | kb.list             |
+| /kb backup  | kb.backup           |
+| /kb incbak  | kb.incbak           |
 | /kb restore | kb.restore          |
-| /kb delete | kb.delete           |
+| /kb delete  | kb.delete           |
 | /kb confirm | kb.confirm          |
-| /kb cancel | kb.cancel           |
-| /kb prev   | kb.prev             |
+| /kb cancel  | kb.cancel           |
+| /kb prev    | kb.prev             |
 
-## 2.2 Script for auto-restart after restoring
+## 2.2 Configurations
+
+Since version `1.8.0`, plugin-wide config file `kbackup.json` is added in the server root directory (workdir).
+
+The config file will be generated if not exist. The default is:
+
+```json
+{
+  "incbak_cow": false
+}
+```
+
+- `incbak_cow`: (experimental) Enable filesystem CoW (copy-on-write) for incremental backup.
+  **Will fall back to normal file copy if the filesystem does not support CoW.** Please read section 2.5 for more info.
+
+Note: JSON comment is **NOT** supported for now.
+
+## 2.3 Script for auto-restart after restoring
 
 Due to the nature of JVM: the Java language's running environment, there is no elegant way to restart Minecraft server
 in a server plugin. In order to auto restart after restoring, an outer system-based script is required, i.e. a batch or
@@ -88,7 +106,7 @@ exit code and restart Minecraft server if the code is `111`.
 I will give examples for some popular operating systems. To use these scripts, you should replace your start.bat or
 start.sh script with given code lines.
 
-### 2.2.1 Script for Windows (Batch script)
+### 2.3.1 Script for Windows (Batch script)
 
 ```batch
 @echo off
@@ -100,7 +118,7 @@ rem kbackup restore auto restart
 pause
 ```
 
-### 2.2.2 Script for Linux (Shell script)
+### 2.3.2 Script for Linux (Shell script)
 
 ```shell
 #!/bin/sh
@@ -112,13 +130,17 @@ do
 done
 ```
 
-## 2.3 Automatic Regular Backup
+## 2.4 Automatic Regular Backup
 
-Currently KBackup does not support automatic backup by itself. However, If application level scheduled tasks are available to you, such as *crontab* in Linux and *Task Scheduler* in Windows, you can use that to trigger backup tasks regularly.
+Currently, KBackup does not support automatic backup by itself. However, If application level scheduled tasks are
+available to you, such as *crontab* in Linux and *Task Scheduler* in Windows, you can use that to trigger backup tasks
+regularly.
 
-### 2.3.1 On Linux
+### 2.4.1 On Linux
 
-In order to run Minecraft command on your server as a Shell command, you need RCON client like [mcrcon](https://github.com/Tiiffi/mcrcon). You can get the binary executable from its homepage and put it into anywhere like `/usr/bin`.
+In order to run Minecraft command on your server as a Shell command, you need RCON client
+like [mcrcon](https://github.com/Tiiffi/mcrcon). You can get the binary executable from its homepage and put it into
+anywhere like `/usr/bin`.
 
 Let's assume you are under Linux, run `crontab -e` and append this line to the configuration:
 
@@ -128,13 +150,34 @@ Let's assume you are under Linux, run `crontab -e` and append this line to the c
 
 You can specify RCON port and password in `server.properties`.
 
-This will cause `cron` to run `kb backup` for every 6 hours. To make incremental backups, simply replace `kb backup` to `kb incbak`.
+This will cause `cron` to run `kb backup` for every 6 hours. To make incremental backups, simply replace `kb backup`
+to `kb incbak`.
+
+The man page [crontab(5)](https://man7.org/linux/man-pages/man5/crontab.5.html) also contains useful information
+about using cron.
+
+### 2.4.2 On Windows
+
+For Windows users, please refer
+to [tutorials available on Google](https://www.google.com/search?q=create+scheduled+task+in+windows) for creating
+scheduled tasks. Note that mcrcon is also available on Windows.
+
+## 2.5 Copy-on-write (CoW) backup
+
+CoW will save even more disk space when making backups.
+
+This feature requires platform-specific library [KBackup-cow](https://github.com/keuin/KBackup-cow).
+Currently only Linux on x86_64 platform is supported.
+Please create a GitHub issue if you want other platforms.
 
-The man page [crontab(5)](https://man7.org/linux/man-pages/man5/crontab.5.html) also contains many useful information about using cron.
+This is an experimental feature. Please report if you encountered any error.
 
-### 2.3.2 On Windows
+Requirements:
 
-For Windows users, please refer to [tutorials available on Google](https://www.google.com/search?q=create+scheduled+task+in+windows) for creating scheduled tasks. Note that mcrcon is also available on Windows.
+1. The server is running Linux on amd64.
+2. Filesystem should support CoW (e.g. Bcachefs, Btrfs, XFS, OCFS2, ReFSv2). Please
+   read <https://www.ctrl.blog/entry/file-cloning.html> for more info about CoW filesystems.
+3. Backup directory and server world directory should on the same disk partition. This is required to clone a file.
 
 # 3. To-Do List
 
diff --git a/build.gradle b/build.gradle
index 67b3e86..ce89a4e 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,7 @@
 plugins {
     id 'fabric-loom' version '1.0-SNAPSHOT'
     id 'maven-publish'
+    id 'com.github.johnrengelman.shadow' version '7.1.2'
 }
 
 sourceCompatibility = JavaVersion.VERSION_1_8
@@ -20,6 +21,20 @@ repositories {
     // for more information about repositories.
 }
 
+shadowJar {
+    configurations = [project.configurations.shadow]
+
+    // mitigate log4j security problem
+    exclude 'org/apache/logging/log4j/core/lookup/JndiLookup.class'
+    exclude 'META-INF'
+}
+
+remapJar {
+    dependsOn(shadowJar)
+    mustRunAfter(shadowJar)
+    inputFile = tasks.shadowJar.archiveFile
+}
+
 dependencies {
     implementation 'junit:junit:4.13.2'
 
@@ -31,6 +46,10 @@ dependencies {
     // Fabric API. This is technically optional, but you probably want it anyway.
     modImplementation "net.fabricmc.fabric-api:fabric-api:${project.fabric_version}"
 
+    // https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind
+    modImplementation 'com.fasterxml.jackson.core:jackson-databind:2.13.5'
+    shadow 'com.fasterxml.jackson.core:jackson-databind:2.13.5'
+
     // Uncomment the following line to enable the deprecated Fabric API modules.
     // These are included in the Fabric API production distribution and allow you to update your mod to the latest modules at a later more convenient time.
 
@@ -54,7 +73,7 @@ java {
 
 jar {
     from("LICENSE") {
-        rename { "${it}_${project.archivesBaseName}"}
+        rename { "${it}_${project.archivesBaseName}" }
     }
 }
 
diff --git a/gradle.properties b/gradle.properties
index 81cb9b8..f9215ba 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -6,7 +6,7 @@ minecraft_version=1.14.4
 yarn_mappings=1.14.4+build.18
 loader_version=0.14.12
 # Mod Properties
-mod_version=1.7.0
+mod_version=1.8.0
 maven_group=com.keuin.kbackupfabric
 archives_base_name=kbackup-fabric
 # Dependencies
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index ffed3a2..db9a6b8 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java b/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
index 5bf92e4..7e454d2 100644
--- a/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
+++ b/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
@@ -58,6 +58,10 @@ public final class KBCommandsRegister {
                         .requires(Permissions.require("kb.list", DEFAULT_REQUIRED_LEVEL))
                         .executes(KBCommands::list)));
 
+        dispatcher.register(CommandManager.literal("kb")
+                .then(CommandManager.literal("cow-info")
+                        .executes(KBCommands::cowInfo)));
+
         // register /kb delete [name] for deleting an existing backup. OP is required.
         dispatcher.register(CommandManager.literal("kb")
                 .then(CommandManager.literal("delete")
diff --git a/src/main/java/com/keuin/kbackupfabric/KBPluginEvents.java b/src/main/java/com/keuin/kbackupfabric/KBPluginEvents.java
index 362abb8..20e9058 100644
--- a/src/main/java/com/keuin/kbackupfabric/KBPluginEvents.java
+++ b/src/main/java/com/keuin/kbackupfabric/KBPluginEvents.java
@@ -2,6 +2,7 @@ package com.keuin.kbackupfabric;
 
 import com.keuin.kbackupfabric.backup.BackupFilesystemUtil;
 import com.keuin.kbackupfabric.backup.suggestion.BackupNameSuggestionProvider;
+import com.keuin.kbackupfabric.config.KBackupConfig;
 import com.keuin.kbackupfabric.event.OnPlayerConnect;
 import com.keuin.kbackupfabric.metadata.BackupMetadata;
 import com.keuin.kbackupfabric.metadata.MetadataHolder;
@@ -32,7 +33,15 @@ public final class KBPluginEvents implements ModInitializer {
 
     @Override
     public void onInitialize() {
-        System.out.println("Binding events and commands ...");
+        PrintUtil.info("Reading config...");
+        try {
+            KBackupConfig.load();
+        } catch (IOException e) {
+            PrintUtil.error("Failed to read config file, using default values: " + e + e.getMessage());
+        }
+        boolean incCow = KBackupConfig.getInstance().getIncbakCow();
+        PrintUtil.info("Incremental backup CoW: " + (incCow ? "enabled" : "disabled"));
+        PrintUtil.info("Binding events and commands...");
         CommandRegistrationCallback.EVENT.register(KBCommandsRegister::registerCommands);
         OnPlayerConnect.ON_PLAYER_CONNECT.register((connection, player)
                 -> NotificationManager.INSTANCE.notifyPlayer(DistinctNotifiable.fromServerPlayerEntity(player)));
diff --git a/src/main/java/com/keuin/kbackupfabric/backup/incremental/manager/IncrementalBackupStorageManager.java b/src/main/java/com/keuin/kbackupfabric/backup/incremental/manager/IncrementalBackupStorageManager.java
index 7870620..53143f8 100644
--- a/src/main/java/com/keuin/kbackupfabric/backup/incremental/manager/IncrementalBackupStorageManager.java
+++ b/src/main/java/com/keuin/kbackupfabric/backup/incremental/manager/IncrementalBackupStorageManager.java
@@ -4,15 +4,18 @@ import com.keuin.kbackupfabric.backup.incremental.ObjectCollection2;
 import com.keuin.kbackupfabric.backup.incremental.ObjectCollectionIterator;
 import com.keuin.kbackupfabric.backup.incremental.ObjectElement;
 import com.keuin.kbackupfabric.backup.incremental.identifier.ObjectIdentifier;
+import com.keuin.kbackupfabric.config.KBackupConfig;
 import com.keuin.kbackupfabric.util.FilesystemUtil;
 import com.keuin.kbackupfabric.util.PrintUtil;
+import com.keuin.kbackupfabric.util.cow.FileCopier;
+import com.keuin.kbackupfabric.util.cow.FileCowCopier;
+import com.keuin.kbackupfabric.util.cow.FileEagerCopier;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.*;
 import java.util.logging.Logger;
@@ -27,9 +30,26 @@ public class IncrementalBackupStorageManager {
     private final Logger logger = Logger.getLogger(IncrementalBackupStorageManager.class.getName());
     private final Path backupStorageBase;
     private final Logger LOGGER = Logger.getLogger(IncrementalBackupStorageManager.class.getName());
+    private FileCopier copier;
 
     public IncrementalBackupStorageManager(Path backupStorageBase) {
         this.backupStorageBase = backupStorageBase;
+        if (KBackupConfig.getInstance().getIncbakCow()) {
+            // try to use cow copier, if failed, fallback to normal copier
+            try {
+                this.copier = FileCowCopier.getInstance();
+            } catch (Exception | UnsatisfiedLinkError ex) {
+                PrintUtil.error("Failed to initialize kbackup-cow: " + ex + ex.getMessage());
+                this.copier = new FileEagerCopier();
+            }
+        } else {
+            this.copier = new FileEagerCopier();
+        }
+        if (this.copier.isCow()) {
+            PrintUtil.info("Copy-on-write is enabled");
+        } else {
+            PrintUtil.info("Copy-on-write is disabled");
+        }
     }
 
     /**
@@ -85,7 +105,7 @@ public class IncrementalBackupStorageManager {
             if (!contains(entry.getValue())) {
                 // element does not exist. copy.
                 logger.fine("Copy new file `" + copySourceFile.getName() + "`.");
-                Files.copy(copySourceFile.toPath(), copyDestination.toPath());
+                copier.copy(copyDestination.getAbsolutePath(), copySourceFile.getAbsolutePath());
                 copyCount = copyCount.addWith(new IncCopyResult(1, 1, fileBytes, fileBytes));
             } else {
                 // element exists (file reused). Just update the stat info
@@ -198,7 +218,7 @@ public class IncrementalBackupStorageManager {
                 }
             }
 
-            Files.copy(copySource.toPath(), copyTarget.toPath());
+            copier.copy(copyTarget.getAbsolutePath(), copySource.getAbsolutePath());
             ++copyCount;
         }
 
diff --git a/src/main/java/com/keuin/kbackupfabric/config/KBackupConfig.java b/src/main/java/com/keuin/kbackupfabric/config/KBackupConfig.java
new file mode 100644
index 0000000..8ece8d2
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/config/KBackupConfig.java
@@ -0,0 +1,56 @@
+package com.keuin.kbackupfabric.config;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
+import com.keuin.kbackupfabric.util.PrintUtil;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class KBackupConfig {
+
+    private static KBackupConfig instance = getDefault();
+    private static final String CONFIG_FILE = "kbackup.json";
+
+    @JsonProperty("incbak_cow")
+    private Boolean incbakCow;
+
+    public static KBackupConfig getInstance() {
+        return instance;
+    }
+
+    private static KBackupConfig getDefault() {
+        return new KBackupConfig(false);
+    }
+
+    public static void load() throws IOException {
+        File file = new File(CONFIG_FILE);
+        ObjectMapper om = new ObjectMapper();
+        try {
+            instance = om.readValue(file, KBackupConfig.class);
+        } catch (FileNotFoundException ignored) {
+            // generate default config file
+            PrintUtil.info("Config file does not exist. Creating default config: " + CONFIG_FILE);
+            instance = getDefault();
+            ObjectWriter w = om.writerWithDefaultPrettyPrinter();
+            w.writeValue(file, instance);
+        }
+    }
+
+    public KBackupConfig() {
+    }
+
+    public KBackupConfig(Boolean incbakCow) {
+        this.incbakCow = incbakCow;
+    }
+
+    public Boolean getIncbakCow() {
+        return this.incbakCow;
+    }
+
+    public void setIncbakCow(Boolean incbakCow) {
+        this.incbakCow = incbakCow;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
index cfc9b81..3d9007d 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
@@ -99,6 +99,7 @@ public class ConfiguredIncrementalBackupMethod implements ConfiguredBackupMethod
             PrintUtil.info("Incremental backup finished.");
             feedback = new IncrementalBackupFeedback(true, copyResult);
         } catch (IOException e) {
+            PrintUtil.error("Incremental backup failed: " + e + e.getMessage());
             feedback = new IncrementalBackupFeedback(e);
         }
 
diff --git a/src/main/java/com/keuin/kbackupfabric/ui/KBCommands.java b/src/main/java/com/keuin/kbackupfabric/ui/KBCommands.java
index d23a6fd..0dff99a 100644
--- a/src/main/java/com/keuin/kbackupfabric/ui/KBCommands.java
+++ b/src/main/java/com/keuin/kbackupfabric/ui/KBCommands.java
@@ -14,6 +14,7 @@ import com.keuin.kbackupfabric.operation.backup.method.ConfiguredIncrementalBack
 import com.keuin.kbackupfabric.operation.backup.method.ConfiguredPrimitiveBackupMethod;
 import com.keuin.kbackupfabric.util.DateUtil;
 import com.keuin.kbackupfabric.util.PrintUtil;
+import com.keuin.kbackupfabric.util.cow.FileCowCopier;
 import com.mojang.brigadier.arguments.StringArgumentType;
 import com.mojang.brigadier.context.CommandContext;
 import net.minecraft.server.MinecraftServer;
@@ -75,6 +76,7 @@ public final class KBCommands {
         msgInfo(context, "/kb restore <backup_name> - Delete the whole current level and restore from given backup. /kb restore is identical with /kb list.");
         msgInfo(context, "/kb confirm - Confirm and start restoring.");
         msgInfo(context, "/kb cancel - Cancel the restoration to be confirmed. If cancelled, /kb confirm will not run.");
+        msgInfo(context, "/kb cow-info - Display copy-on-write support info (Experimental)");
         return SUCCESS;
     }
 
@@ -135,6 +137,15 @@ public final class KBCommands {
         return SUCCESS;
     }
 
+    public static int cowInfo(CommandContext<ServerCommandSource> context) {
+        try {
+            msgInfo(context, "KBackup-cow library version: " + FileCowCopier.getVersion());
+        } catch (Exception | UnsatisfiedLinkError ignored) {
+            msgErr(context, "KBackup-cow library is not loaded");
+        }
+        return SUCCESS;
+    }
+
     /**
      * Print backup information.
      *
diff --git a/src/main/java/com/keuin/kbackupfabric/util/cow/FileCopier.java b/src/main/java/com/keuin/kbackupfabric/util/cow/FileCopier.java
new file mode 100644
index 0000000..eb21af7
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/cow/FileCopier.java
@@ -0,0 +1,9 @@
+package com.keuin.kbackupfabric.util.cow;
+
+import java.io.IOException;
+
+public interface FileCopier {
+    void copy(String dst, String src) throws IOException;
+
+    boolean isCow();
+}
diff --git a/src/main/java/com/keuin/kbackupfabric/util/cow/FileCowCopier.java b/src/main/java/com/keuin/kbackupfabric/util/cow/FileCowCopier.java
new file mode 100644
index 0000000..e5819de
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/cow/FileCowCopier.java
@@ -0,0 +1,44 @@
+package com.keuin.kbackupfabric.util.cow;
+
+import com.keuin.kbackupfabric.util.PrintUtil;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public final class FileCowCopier {
+    private static final AtomicBoolean initialized = new AtomicBoolean(false);
+
+    static {
+        try {
+            System.loadLibrary("kbackup_cow");
+        } catch (SecurityException | UnsatisfiedLinkError ignored) {
+        }
+    }
+
+    public static native void init();
+
+    public static native void copy(String dst, String src) throws IOException;
+
+    public static native String getVersion();
+
+    public static FileCopier getInstance() {
+        if (initialized.compareAndSet(false, true)) {
+            FileCowCopier.init();
+            PrintUtil.info("kbackup-cow version: " + FileCowCopier.getVersion());
+        }
+        // call a native method to ensure the dynamic library is correctly loaded, JVM will throw if failed
+        // so the outside fallback logic could work
+        FileCowCopier.getVersion();
+        return new FileCopier() {
+            @Override
+            public void copy(String dst, String src) throws IOException {
+                FileCowCopier.copy(dst, src);
+            }
+
+            @Override
+            public boolean isCow() {
+                return true;
+            }
+        };
+    }
+}
diff --git a/src/main/java/com/keuin/kbackupfabric/util/cow/FileEagerCopier.java b/src/main/java/com/keuin/kbackupfabric/util/cow/FileEagerCopier.java
new file mode 100644
index 0000000..0f12374
--- /dev/null
+++ b/src/main/java/com/keuin/kbackupfabric/util/cow/FileEagerCopier.java
@@ -0,0 +1,17 @@
+package com.keuin.kbackupfabric.util.cow;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+public class FileEagerCopier implements FileCopier {
+    @Override
+    public void copy(String dst, String src) throws IOException {
+        Files.copy(Paths.get(src), Paths.get(dst));
+    }
+
+    @Override
+    public boolean isCow() {
+        return false;
+    }
+}