+ akka-persistence: add internal message protocol traits

* resolve #16612

akka-persistence/src/main/scala/akka/persistence/JournalProtocol.scala

@@ -14,10 +14,19 @@ import akka.actor._
  * Messages exchanged between persistent actors, views and a journal.
  */
 private[persistence] object JournalProtocol {
+
+  /** Marker trait shared by internal journal messages. */
+  sealed trait Message extends Protocol.Message
+  /** Internal journal command. */
+  sealed trait Request extends Message
+  /** Internal journal acknowledgement. */
+  sealed trait Response extends Message
+
   /**
    * Reply message to a failed [[DeleteMessages]] request.
    */
   final case class DeleteMessagesFailure(cause: Throwable)
+    extends Response
 
   /**
    * Request to delete all persistent messages with sequence numbers up to `toSequenceNr`
@@ -25,6 +34,7 @@ private[persistence] object JournalProtocol {
    * as deleted in the journal, otherwise they are permanently deleted from the journal.
    */
   final case class DeleteMessagesTo(persistenceId: String, toSequenceNr: Long, permanent: Boolean)
+    extends Request
 
   /**
    * Request to write messages.
@@ -33,12 +43,14 @@ private[persistence] object JournalProtocol {
    * @param persistentActor write requestor.
    */
   final case class WriteMessages(messages: immutable.Seq[PersistentEnvelope], persistentActor: ActorRef, actorInstanceId: Int)
+    extends Request
 
   /**
    * Reply message to a successful [[WriteMessages]] request. This reply is sent to the requestor
    * before all subsequent [[WriteMessageSuccess]] replies.
    */
   case object WriteMessagesSuccessful
+    extends Response
 
   /**
    * Reply message to a failed [[WriteMessages]] request. This reply is sent to the requestor
@@ -47,6 +59,7 @@ private[persistence] object JournalProtocol {
    * @param cause failure cause.
    */
   final case class WriteMessagesFailed(cause: Throwable)
+    extends Response
 
   /**
    * Reply message to a successful [[WriteMessages]] request. For each contained [[PersistentRepr]] message
@@ -55,6 +68,7 @@ private[persistence] object JournalProtocol {
    * @param persistent successfully written message.
    */
   final case class WriteMessageSuccess(persistent: PersistentRepr, actorInstanceId: Int)
+    extends Response
 
   /**
    * Reply message to a failed [[WriteMessages]] request. For each contained [[PersistentRepr]] message
@@ -64,6 +78,7 @@ private[persistence] object JournalProtocol {
    * @param cause failure cause.
    */
   final case class WriteMessageFailure(message: PersistentRepr, cause: Throwable, actorInstanceId: Int)
+    extends Response
 
   /**
    * Reply message to a [[WriteMessages]] with a non-persistent message.
@@ -71,6 +86,7 @@ private[persistence] object JournalProtocol {
    * @param message looped message.
    */
   final case class LoopMessageSuccess(message: Any, actorInstanceId: Int)
+    extends Response
 
   /**
    * Request to replay messages to `persistentActor`.
@@ -83,6 +99,7 @@ private[persistence] object JournalProtocol {
    * @param replayDeleted `true` if messages marked as deleted shall be replayed.
    */
   final case class ReplayMessages(fromSequenceNr: Long, toSequenceNr: Long, max: Long, persistenceId: String, persistentActor: ActorRef, replayDeleted: Boolean = false)
+    extends Request
 
   /**
    * Reply message to a [[ReplayMessages]] request. A separate reply is sent to the requestor for each
@@ -91,18 +108,21 @@ private[persistence] object JournalProtocol {
    * @param persistent replayed message.
    */
   final case class ReplayedMessage(persistent: PersistentRepr)
+    extends Response
 
   /**
    * Reply message to a successful [[ReplayMessages]] request. This reply is sent to the requestor
    * after all [[ReplayedMessage]] have been sent (if any).
    */
   case object ReplayMessagesSuccess
+    extends Response
 
   /**
    * Reply message to a failed [[ReplayMessages]] request. This reply is sent to the requestor
    * if a replay could not be successfully completed.
    */
   final case class ReplayMessagesFailure(cause: Throwable)
+    extends Response
 
   /**
    * Request to read the highest stored sequence number of a given persistent actor.
@@ -112,6 +132,7 @@ private[persistence] object JournalProtocol {
    * @param persistentActor requesting persistent actor.
    */
   final case class ReadHighestSequenceNr(fromSequenceNr: Long = 1L, persistenceId: String, persistentActor: ActorRef)
+    extends Request
 
   /**
    * Reply message to a successful [[ReadHighestSequenceNr]] request.
@@ -119,6 +140,7 @@ private[persistence] object JournalProtocol {
    * @param highestSequenceNr read highest sequence number.
    */
   final case class ReadHighestSequenceNrSuccess(highestSequenceNr: Long)
+    extends Response
 
   /**
    * Reply message to a failed [[ReadHighestSequenceNr]] request.
@@ -126,5 +148,5 @@ private[persistence] object JournalProtocol {
    * @param cause failure cause.
    */
   final case class ReadHighestSequenceNrFailure(cause: Throwable)
+    extends Response
 }
-

akka-persistence/src/main/scala/akka/persistence/Protocol.scala

@@ -0,0 +1,24 @@
+/**
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.persistence
+
+/**
+ * INTERNAL API.
+ *
+ * Messages exchanged between persistent actors, views and a journal/snapshot-store.
+ */
+private[persistence] object Protocol {
+
+  /**
+   * INTERNAL API.
+   *
+   * Internal persistence extension messages extend this trait.
+   *
+   * Helps persistence plugin developers to differentiate
+   * internal persistence extension messages from their custom plugin messages.
+   */
+  trait Message
+
+}

akka-persistence/src/main/scala/akka/persistence/SnapshotProtocol.scala

@@ -12,7 +12,8 @@ package akka.persistence
  * @param sequenceNr sequence number at which the snapshot was taken.
  * @param timestamp time at which the snapshot was saved.
  */
-@SerialVersionUID(1L) //#snapshot-metadata
+@SerialVersionUID(1L) //
+//#snapshot-metadata
 final case class SnapshotMetadata(persistenceId: String, sequenceNr: Long, timestamp: Long = 0L)
 //#snapshot-metadata
 
@@ -113,6 +114,14 @@ object SelectedSnapshot {
  * Defines messages exchanged between persistent actors and a snapshot store.
  */
 private[persistence] object SnapshotProtocol {
+
+  /** Marker trait shared by internal snapshot messages. */
+  sealed trait Message extends Protocol.Message
+  /** Internal snapshot command. */
+  sealed trait Request extends Message
+  /** Internal snapshot acknowledgement. */
+  sealed trait Response extends Message
+
   /**
    * Instructs a snapshot store to load a snapshot.
    *
@@ -121,6 +130,7 @@ private[persistence] object SnapshotProtocol {
    * @param toSequenceNr upper sequence number bound (inclusive) for recovery.
    */
   final case class LoadSnapshot(persistenceId: String, criteria: SnapshotSelectionCriteria, toSequenceNr: Long)
+    extends Request
 
   /**
    * Response message to a [[LoadSnapshot]] message.
@@ -128,6 +138,7 @@ private[persistence] object SnapshotProtocol {
    * @param snapshot loaded snapshot, if any.
    */
   final case class LoadSnapshotResult(snapshot: Option[SelectedSnapshot], toSequenceNr: Long)
+    extends Response
 
   /**
    * Instructs snapshot store to save a snapshot.
@@ -136,6 +147,7 @@ private[persistence] object SnapshotProtocol {
    * @param snapshot snapshot.
    */
   final case class SaveSnapshot(metadata: SnapshotMetadata, snapshot: Any)
+    extends Request
 
   /**
    * Instructs snapshot store to delete a snapshot.
@@ -143,6 +155,7 @@ private[persistence] object SnapshotProtocol {
    * @param metadata snapshot metadata.
    */
   final case class DeleteSnapshot(metadata: SnapshotMetadata)
+    extends Request
 
   /**
    * Instructs snapshot store to delete all snapshots that match `criteria`.
@@ -151,4 +164,5 @@ private[persistence] object SnapshotProtocol {
    * @param criteria criteria for selecting snapshots to be deleted.
    */
   final case class DeleteSnapshots(persistenceId: String, criteria: SnapshotSelectionCriteria)
+    extends Request
 }