From a8700ddc934c42223c3533bd858c39202d0072bf Mon Sep 17 00:00:00 2001
From: Jonas Boner <jonas@jonasboner.com>
Date: Mon, 23 Mar 2009 19:17:10 +0100
Subject: [PATCH] initial draft of transactional actors

---
 kernel/src/main/scala/Transaction.scala | 93 +++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 kernel/src/main/scala/Transaction.scala

diff --git a/kernel/src/main/scala/Transaction.scala b/kernel/src/main/scala/Transaction.scala
new file mode 100644
index 0000000000..3e4fed16f3
--- /dev/null
+++ b/kernel/src/main/scala/Transaction.scala
@@ -0,0 +1,93 @@
+/**
+ * Copyright (C) 2009 Scalable Solutions.
+ */
+
+package se.scalablesolutions.akka.kernel
+
+import java.util.concurrent.atomic.AtomicLong
+import scala.collection.mutable.HashMap
+
+sealed abstract case class TransactionStatus
+object TransactionStatus {
+  case object New extends TransactionStatus
+  case object Active extends TransactionStatus
+  case object Aborted extends TransactionStatus
+  case object Completed extends TransactionStatus
+}
+
+/**
+ * Represents a snapshot of the current invocation.
+ *
+ * @author <a href="http://jonasboner.com">Jonas Bon&#233;r</a>
+ */
+object TransactionIdFactory {
+  private val currentId = new AtomicLong(0L)
+  def newId = currentId.getAndIncrement
+}
+
+/**
+ * Represents a snapshot of the current invocation.
+ *
+ * @author <a href="http://jonasboner.com">Jonas Bon&#233;r</a>
+ */
+class Transaction extends Logging {
+  val id = TransactionIdFactory.newId
+  
+  private[this] var parent: Option[Transaction] = None
+  private[this] var oldActorVersions = new HashMap[GenericServerContainer, GenericServer]
+  private[this] var precommitted: List[GenericServerContainer] = Nil
+  @volatile private[this] var status: TransactionStatus = TransactionStatus.New
+
+  def begin(server: GenericServerContainer) = synchronized {
+    if (status == TransactionStatus.Aborted) throw new IllegalStateException("Can't begin ABORTED transaction")
+    if (status == TransactionStatus.Completed) throw new IllegalStateException("Can't begin COMPLETED transaction")
+    if (status == TransactionStatus.New) log.debug("Actor [%s] is starting NEW transaction", server)
+    else log.debug("Actor [%s] is participating in transaction", server)
+    val oldVersion = server.cloneServerAndReturnOldVersion
+    oldActorVersions.put(server, oldVersion)
+    status = TransactionStatus.Active
+  }
+
+  def precommit(server: GenericServerContainer) = synchronized {
+    ensureIsActive
+    log.debug("Pre-committing transaction for actor [%s]", server)
+    precommitted ::= server
+  }
+
+  def commit(server: GenericServerContainer) = synchronized {
+    ensureIsActive
+    log.debug("Committing transaction for actor [%s]", server)
+    val haveAllPreCommitted =
+      if (oldActorVersions.size == precommitted.size) {{
+        for (server <- oldActorVersions.keys) yield {
+          if (precommitted.exists(_.id == server.id)) true
+          else false
+        }}.exists(_ == false)
+      } else false
+      
+    if (haveAllPreCommitted) status = TransactionStatus.Completed
+    else rollback(server)
+  }
+
+  def rollback(server: GenericServerContainer) = synchronized {
+    ensureIsActive
+    log.debug("Actor [%s] has initiated transaction rollback, rolling back [%s]" , server, oldActorVersions.keys)
+    oldActorVersions.foreach(entry => {
+        val (server, backup) = entry
+        server.swapServer(backup)
+    })
+    status = TransactionStatus.Aborted
+  }
+
+  private def ensureIsActive = if (status == TransactionStatus.Active) 
+    throw new IllegalStateException("Expected ACTIVE transaction - current status [" + status + "]")
+
+  override def equals(that: Any): Boolean = 
+    that != null && 
+    that.isInstanceOf[Transaction] && 
+    that.asInstanceOf[Transaction].id == this.id
+ 
+  override def hashCode(): Int = id.toInt
+ 
+  override def toString(): String = "Transaction[" + id + ", " + status + "]"
+}