a few more things when reviewing replicated event sourcing (#29461)

akka-actor/src/main/scala/akka/util/AlwaysIncreasingClock.scala

@@ -1,29 +0,0 @@
-/*
- * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
- */
-
-package akka.util
-
-import java.util.concurrent.atomic.AtomicLong
-import java.util.function.LongUnaryOperator
-
-import akka.annotation.InternalApi
-
-/**
- * Always increasing wall clock time.
- */
-@InternalApi
-private[akka] final class AlwaysIncreasingClock() extends AtomicLong with WallClock {
-
-  override def currentTimeMillis(): Long = {
-    val currentSystemTime = System.currentTimeMillis()
-    updateAndGet {
-      new LongUnaryOperator {
-        override def applyAsLong(time: Long): Long = {
-          if (currentSystemTime <= time) time + 1
-          else currentSystemTime
-        }
-      }
-    }
-  }
-}

akka-actor/src/main/scala/akka/util/WallClock.scala

@@ -5,6 +5,10 @@
 package akka.util
 
 import akka.annotation.ApiMayChange
+import java.util.concurrent.atomic.AtomicLong
+import java.util.function.LongUnaryOperator
+
+import akka.annotation.InternalApi
 
 /**
  * A time source.
@@ -17,7 +21,27 @@ trait WallClock {
 object WallClock {
 
   /**
-   * Always increasing time source.
+   * Always increasing time source. Based on `System.currentTimeMillis()` but
+   * guaranteed to always increase for each invocation.
    */
   val AlwaysIncreasingClock: WallClock = new AlwaysIncreasingClock()
 }
+
+/**
+ * INTERNAL API: Always increasing wall clock time.
+ */
+@InternalApi
+private[akka] final class AlwaysIncreasingClock() extends AtomicLong with WallClock {
+
+  override def currentTimeMillis(): Long = {
+    val currentSystemTime = System.currentTimeMillis()
+    updateAndGet {
+      new LongUnaryOperator {
+        override def applyAsLong(time: Long): Long = {
+          if (currentSystemTime <= time) time + 1
+          else currentSystemTime
+        }
+      }
+    }
+  }
+}

akka-docs/src/main/paradox/typed/guide/modules.md

@@ -21,12 +21,10 @@ With a [Lightbend Platform Subscription](https://www.lightbend.com/lightbend-sub
 * [Configuration Checker](https://doc.akka.io/docs/akka-enhancements/current/config-checker.html) — Checks for potential configuration issues and logs suggestions.
 * [Diagnostics Recorder](https://doc.akka.io/docs/akka-enhancements/current/diagnostics-recorder.html) — Captures configuration and system information in a format that makes it easy to troubleshoot issues during development and production.
 * [Thread Starvation Detector](https://doc.akka.io/docs/akka-enhancements/current/starvation-detector.html) — Monitors an Akka system dispatcher and logs warnings if it becomes unresponsive.
-* [Kubernetes Lease](https://doc.akka.io/docs/akka-enhancements/current/kubernetes-lease.html) — Monitors an Akka system dispatcher and logs warnings if it becomes unresponsive.
 * [Fast Failover](https://doc.akka.io/docs/akka-enhancements/current/fast-failover.html) — Fast failover for Cluster Sharding.
 
 [Akka Persistence Enhancements](https://doc.akka.io/docs/akka-enhancements/current/akka-persistence-enhancements.html):
 
-* [Multi-DC Persistence](https://doc.akka.io/docs/akka-enhancements/current/persistence-dc/index.html) — For active-active persistent entities across multiple data centers.
 * [GDPR for Akka Persistence](https://doc.akka.io/docs/akka-enhancements/current/gdpr/index.html) — Data shredding can be used to forget information in events.
 
 This page does not list all available modules, but overviews the main functionality and gives you an idea of the level of sophistication you can reach when you start building systems on top of Akka.

akka-docs/src/main/paradox/typed/persistence.md

@@ -657,9 +657,9 @@ cluster and address them by id.
 Akka Persistence is based on the single-writer principle. For a particular `PersistenceId` only one `EventSourcedBehavior`
 instance should be active at one time. If multiple instances were to persist events at the same time, the events would
 be interleaved and might not be interpreted correctly on replay. Cluster Sharding ensures that there is only one
-active entity (`EventSourcedBehavior`) for each id within a data center. Lightbend's
+active entity (`EventSourcedBehavior`) for each id within a data center.
-[Multi-DC Persistence](https://doc.akka.io/docs/akka-enhancements/current/persistence-dc/index.html)
+@ref:[Replicated Event Sourcing](replicated-eventsourcing.md) supports active-active persistent entities across
-supports active-active persistent entities across data centers.
+data centers.
 
 ## Configuration
 
@@ -684,5 +684,5 @@ from the events, or publish the events to other services.
 
 @java[@extref[Multi-DC Persistence example project](samples:akka-samples-persistence-dc-java)]
 @scala[@extref[Multi-DC Persistence example project](samples:akka-samples-persistence-dc-scala)]
-illustrates how to use Lightbend's [Multi-DC Persistence](https://doc.akka.io/docs/akka-enhancements/current/persistence-dc/index.html)
+illustrates how to use @ref:[Replicated Event Sourcing](replicated-eventsourcing.md) that supports
-with active-active persistent entities across data centers.
+active-active persistent entities across data centers.

akka-persistence-typed/src/main/resources/reference.conf

@@ -2,16 +2,16 @@ akka.actor {
 
   serialization-identifiers."akka.persistence.typed.serialization.ReplicatedEventSourcingSerializer" = 40
 
-  serializers.active-active = "akka.persistence.typed.serialization.ReplicatedEventSourcingSerializer"
+  serializers.replicated-event-sourcing = "akka.persistence.typed.serialization.ReplicatedEventSourcingSerializer"
 
   serialization-bindings {
-    "akka.persistence.typed.internal.VersionVector" = active-active
+    "akka.persistence.typed.internal.VersionVector" = replicated-event-sourcing
-    "akka.persistence.typed.crdt.Counter" = active-active
+    "akka.persistence.typed.crdt.Counter" = replicated-event-sourcing
-    "akka.persistence.typed.crdt.Counter$Updated" = active-active
+    "akka.persistence.typed.crdt.Counter$Updated" = replicated-event-sourcing
-    "akka.persistence.typed.crdt.ORSet" = active-active
+    "akka.persistence.typed.crdt.ORSet" = replicated-event-sourcing
-    "akka.persistence.typed.crdt.ORSet$DeltaOp" = active-active
+    "akka.persistence.typed.crdt.ORSet$DeltaOp" = replicated-event-sourcing
-    "akka.persistence.typed.internal.ReplicatedEventMetadata" = active-active
+    "akka.persistence.typed.internal.ReplicatedEventMetadata" = replicated-event-sourcing
-    "akka.persistence.typed.internal.ReplicatedSnapshotMetadata" = active-active
+    "akka.persistence.typed.internal.ReplicatedSnapshotMetadata" = replicated-event-sourcing
   }
 }
 

akka-persistence-typed/src/main/scala/akka/persistence/typed/crdt/ORSet.scala

@@ -32,7 +32,7 @@ object ORSet {
    */
   @InternalApi private[akka] type Dot = VersionVector
 
-  sealed trait DeltaOp extends Serializable {
+  sealed trait DeltaOp {
     def merge(that: DeltaOp): DeltaOp
   }
 
@@ -275,13 +275,11 @@ object ORSet {
  * This class is immutable, i.e. "modifying" methods return a new instance.
  */
 @ApiMayChange
-@SerialVersionUID(1L)
 final class ORSet[A] private[akka] (
     val originReplica: String,
     private[akka] val elementsMap: Map[A, ORSet.Dot],
     private[akka] val vvector: VersionVector)
-    extends OpCrdt[DeltaOp]
+    extends OpCrdt[DeltaOp] {
-    with Serializable {
 
   type T = ORSet[A]
   type D = ORSet.DeltaOp

akka-persistence-typed/src/main/scala/akka/persistence/typed/internal/ReplicationSetup.scala

@@ -14,9 +14,6 @@ import akka.util.ccompat.JavaConverters._
 /**
  * INTERNAL API
  */
-// FIXME, parts of this can be set during initialisation
-// Other fields will be set before executing the event handler as they change per event
-// https://github.com/akka/akka/issues/29258
 @InternalApi
 private[akka] final class ReplicationContextImpl(
     val entityId: String,

akka-persistence-typed/src/main/scala/akka/persistence/typed/internal/Running.scala

@@ -165,7 +165,7 @@ private[akka] object Running {
           // needs to be outside of the restart source so that it actually cancels when terminating the replica
           .via(ActorFlow
             .ask[EventEnvelope, ReplicatedEventEnvelope[E], ReplicatedEventAck.type](ref) { (eventEnvelope, replyTo) =>
-              // Need to handle this not being available migration from non-active-active is supported
+              // Need to handle this not being available migration from non-replicated is supported
               val meta = eventEnvelope.eventMetadata.get.asInstanceOf[ReplicatedEventMetadata]
               val re =
                 ReplicatedEvent[E](

akka-persistence-typed/src/main/scala/akka/persistence/typed/internal/VersionVector.scala

@@ -13,7 +13,7 @@ import akka.annotation.InternalApi
  * VersionVector module with helper classes and methods.
  */
 @InternalApi
-object VersionVector {
+private[akka] object VersionVector {
 
   private val emptyVersions: TreeMap[String, Long] = TreeMap.empty
   val empty: VersionVector = ManyVersionVector(emptyVersions)
@@ -71,9 +71,8 @@ object VersionVector {
  *
  * This class is immutable, i.e. "modifying" methods return a new instance.
  */
-@SerialVersionUID(1L)
 @InternalApi
-sealed abstract class VersionVector extends Serializable {
+private[akka] sealed abstract class VersionVector {
 
   type T = VersionVector