Optimistic locking option

src/main/kotlin/nl/astraeus/persistence/Datastore.kt

@@ -17,16 +17,29 @@ enum class ActionType {
 class TypeData(
   var nextId: AtomicLong = AtomicLong(1L),
   val data: MutableMap<Serializable, Persistable> = ConcurrentHashMap(),
-) : Serializable
+) : Serializable {
+  companion object {
+    private const val serialVersionUID: Long = 1L
+  }
+}
 
 class Action(
   val type: ActionType,
   val obj: Persistable
-) : Serializable
+) : Serializable {
+  override fun toString(): String {
+    return "Action(type=$type, obj=$obj)"
+  }
+
+  companion object {
+    private const val serialVersionUID: Long = 1L
+  }
+}
 
 class Datastore(
   private val directory: File,
   indexes: Array<PersistableIndex> = arrayOf(),
+  val enableOptimisticLocking: Boolean = false,
 ) {
   private val fileManager = FileManager(directory)
   private val transactionFormatter = DecimalFormat("#")
@@ -58,7 +71,8 @@ class Datastore(
 
   fun setMaxId(javaClass: Class<Persistable>, id: Long) {
     val nextId = data.getOrPut(javaClass) { TypeData() }.nextId
-    if (nextId.get() <= id) nextId.set(id + 1)
+    val current = nextId.get()
+    if (current <= id) nextId.addAndGet(id - current)
   }
 
   override fun toString(): String {
@@ -97,15 +111,24 @@ class Datastore(
       }
     }
 
-    Logger.debug("Loaded transactions in ${(System.nanoTime() - start) / 1_000_000}ms")
+    Logger.debug("Loaded transactions in %6.3fms", ((System.nanoTime() - start) / 1_000_000f))
   }
 
-  private fun getTrnx(file: File): Long {
-    return file.name.substringAfterLast('/').substringAfter("transaction-").substringBefore(".").toLong()
-  }
-
-  fun execute(actions: MutableList<Action>) {
+  private fun execute(actions: Set<Action>) {
     synchronized(this) {
+      if (enableOptimisticLocking) {
+        for (action in actions) {
+          val typeData = data.getOrPut(action.obj::class.java) {
+            TypeData()
+          }
+          if (action.type == ActionType.STORE) {
+            if ((typeData.data[action.obj.id]?.version ?: -1L) >= action.obj.version) {
+              throw OptimisticLockingException(action.obj)
+            }
+          }
+        }
+      }
+
       for (action in actions) {
         val typeData = data.getOrPut(action.obj::class.java) {
           TypeData()
@@ -137,7 +160,6 @@ class Datastore(
     }
   }
 
-
   fun <T : Persistable> count(clazz: KClass<T>): Int {
     val typeData = data.getOrPut(clazz.java) {
       TypeData()
@@ -176,25 +198,25 @@ class Datastore(
     return indexes[kClass.java]?.get(indexName)
   }
 
-  fun storeAndExecute(actions: MutableList<Action>) {
+  fun storeAndExecute(actions: Set<Action>) {
     if (actions.isNotEmpty()) {
       synchronized(this) {
-        writeTransaction(actions)
         execute(actions)
+        writeTransaction(actions)
       }
     }
   }
 
   private fun readTransaction(ois: ObjectInputStream) {
     val versionNumber = ois.readInt()
-    check (versionNumber == 1) { "Unsupported version number: $versionNumber" }
+    check(versionNumber == 1) { "Unsupported version number: $versionNumber" }
     val transactionNumber = ois.readLong()
     nextTransactionNumber = transactionNumber + 1
-    val actions = ois.readObject() as MutableList<Action>
+    val actions = ois.readObject() as Set<Action>
     execute(actions)
   }
 
-  private fun writeTransaction(actions: MutableList<Action>) {
+  private fun writeTransaction(actions: Set<Action>) {
     val number = transactionFormatter.format(nextTransactionNumber)
     val file = File(directory, "transaction-$number.trn")
     ObjectOutputStream(file.outputStream()).use { oos ->
@@ -226,12 +248,12 @@ class Datastore(
         }
       }
     }
-    Logger.debug("Snapshot in ${(System.nanoTime() - start) / 1_000_000}ms")
+    Logger.debug("Snapshot in %6.3fms", ((System.nanoTime() - start) / 1_000_000f))
   }
 
   private fun readSnapshot(ois: ObjectInputStream) {
     val versionNumber = ois.readInt()
-    check (versionNumber == 1) { "Unsupported version number: $versionNumber" }
+    check(versionNumber == 1) { "Unsupported version number: $versionNumber" }
     nextTransactionNumber = ois.readLong() + 1
     data.clear()
     data.putAll(ois.readObject() as MutableMap<Class<*>, TypeData>)

src/main/kotlin/nl/astraeus/persistence/Logger.kt

@@ -1,8 +1,62 @@
 package nl.astraeus.nl.astraeus.persistence
 
+enum class LogLevel {
+  TRACE,
+  DEBUG,
+  INFO,
+  WARN,
+  ERROR
+}
+
 object Logger {
-  var debug: (String) -> Unit = { println("DEBUG: $it") }
-  var info: (String) -> Unit = { println("INFO: $it") }
-  var warn: (String) -> Unit = { println("WARN: $it") }
-  var error: (String) -> Unit = { println("ERROR: $it") }
-}
+  var level: LogLevel = LogLevel.DEBUG
+
+  var tracePrinter: (String) -> Unit = { println(it) }
+  var debugPrinter: (String) -> Unit = { println(it) }
+  var infoPrinter: (String) -> Unit = { println(it) }
+  var warnPrinter: (String) -> Unit = { println(it) }
+  var errorPrinter: (String) -> Unit = { System.err.println(it) }
+
+  fun trace(message: String, vararg parameters: Any?) {
+    if (level <= LogLevel.TRACE) {
+      writeLogMessage(LogLevel.TRACE, message, *parameters)
+    }
+  }
+
+  fun debug(message: String, vararg parameters: Any?) {
+    if (level <= LogLevel.DEBUG) {
+      writeLogMessage(LogLevel.DEBUG, message, *parameters)
+    }
+  }
+
+  fun info(message: String, vararg parameters: Any?) {
+    if (level <= LogLevel.INFO) {
+      writeLogMessage(LogLevel.INFO, message, *parameters)
+    }
+  }
+
+  fun warn(message: String, vararg parameters: Any?) {
+    if (level <= LogLevel.DEBUG) {
+      writeLogMessage(LogLevel.DEBUG, message, *parameters)
+    }
+  }
+
+  fun error(message: String, vararg parameters: Any?) {
+    if (level <= LogLevel.ERROR) {
+      writeLogMessage(LogLevel.ERROR, message, *parameters)
+    }
+  }
+
+  private fun writeLogMessage(level: LogLevel, message: String, vararg parameters: Any?) {
+    val formattedMessage = "[${level}] - ${message.format(*parameters)}"
+
+    when (level) {
+      LogLevel.TRACE -> tracePrinter(formattedMessage)
+      LogLevel.DEBUG -> debugPrinter(formattedMessage)
+      LogLevel.INFO -> infoPrinter(formattedMessage)
+      LogLevel.WARN -> warnPrinter(formattedMessage)
+      LogLevel.ERROR -> errorPrinter(formattedMessage)
+    }
+
+  }
+}

src/main/kotlin/nl/astraeus/persistence/OptimisticLockingException.kt

@@ -0,0 +1,18 @@
+package nl.astraeus.nl.astraeus.persistence
+
+class OptimisticLockingException : Exception {
+  constructor(
+    obj: Persistable
+  ) : this("Optimistic locking failed for ${obj.javaClass.simpleName} with id ${obj.id}, version ${obj.version}")
+
+  constructor() : super()
+  constructor(message: String?) : super(message)
+  constructor(message: String?, cause: Throwable?) : super(message, cause)
+  constructor(cause: Throwable?) : super(cause)
+  constructor(message: String?, cause: Throwable?, enableSuppression: Boolean, writableStackTrace: Boolean) : super(
+    message,
+    cause,
+    enableSuppression,
+    writableStackTrace
+  )
+}

src/main/kotlin/nl/astraeus/persistence/Persistable.kt

@@ -17,7 +17,9 @@ interface Persistable : Serializable {
       }
       ByteArrayInputStream(baos.toByteArray()).use { bais ->
         ObjectInputStream(bais).use { ois ->
-          return ois.readObject() as Persistable
+          val result = ois.readObject() as Persistable
+          result.version++
+          return result
         }
       }
     }

src/main/kotlin/nl/astraeus/persistence/Persistent.kt

@@ -11,8 +11,9 @@ fun currentTransaction(): Transaction? {
 class Persistent(
   directory: File,
   indexes: Array<PersistableIndex> = arrayOf(),
+  enableOptimisticLocking: Boolean = false,
 ) {
-  val datastore: Datastore = Datastore(directory, indexes)
+  val datastore: Datastore = Datastore(directory, indexes, enableOptimisticLocking)
 
   fun <T> query(block: Query.() -> T): T {
     return block(Query(this))

src/main/kotlin/nl/astraeus/persistence/Transaction.kt

@@ -95,11 +95,13 @@ open class Query(
 class Transaction(
   persistent: Persistent,
 ) : Query(persistent), Serializable {
-  private val actions = mutableListOf<Action>()
+  private val actions = mutableSetOf<Action>()
 
   fun store(obj: Persistable) {
     if (obj.id == 0L) {
       obj.id = persistent.datastore.getNextId(obj.javaClass)
+    } else if (obj.id > persistent.datastore.getNextId(obj.javaClass)) {
+      persistent.datastore.setMaxId(obj.javaClass, obj.id + 1)
     }
 
     actions.add(Action(ActionType.STORE, obj))

src/main/kotlin/nl/astraeus/persistence/TransactionLog.kt

@@ -0,0 +1,33 @@
+package nl.astraeus.nl.astraeus.persistence
+
+import java.io.File
+import java.io.ObjectInputStream
+
+class TransactionLog(
+  val directory: File,
+) {
+  val fileManager = FileManager(directory)
+
+  fun showTransactions() {
+    fileManager.findLastSnapshot().let { (after, snapshot) ->
+      println("Last snapshot: $snapshot")
+
+      val transactions = fileManager.findTransactionsAfter(after ?: 0L)
+
+      println("Transactions:")
+      transactions?.forEach { transaction ->
+        transaction.inputStream().use { input ->
+          ObjectInputStream(input).use { ois ->
+            val versionNumber = ois.readInt()
+            check(versionNumber == 1) { "Unsupported version number: $versionNumber" }
+            val transactionNumber = ois.readLong()
+            val actions = ois.readObject() as Set<Action>
+            println("[$versionNumber]  $transactionNumber - ${actions.joinToString(",")}")
+          }
+        }
+      }
+    }
+
+  }
+
+}