added v1.4.47 release notes

RELEASE_NOTES.md

@@ -1,3 +1,84 @@
+#### 1.4.47 December 9th 2022 ####
+Akka.NET v1.4.47 is a maintenance patch for Akka.NET v1.4.46 that includes a variety of bug fixes, performance improvements, and new features.
+
+**Actor Telemetry**
+
+Starting in Akka.NET v1.4.47 local and remotely deployed actors will now emit events when being started, stopped, and restarted:
+
+```csharp
+public interface IActorTelemetryEvent : INoSerializationVerificationNeeded, INotInfluenceReceiveTimeout
+{
+    /// <summary>
+    /// The actor who emitted this event.
+    /// </summary>
+    IActorRef Subject {get;}
+
+    /// <summary>
+    /// The implementation type for this actor.
+    /// </summary>
+    Type ActorType { get; }
+}
+
+/// <summary>
+/// Event emitted when actor starts.
+/// </summary>
+public sealed class ActorStarted : IActorTelemetryEvent
+{
+    public IActorRef Subject { get; }
+    public Type ActorType { get; }
+}
+
+/// <summary>
+/// Event emitted when actor shuts down.
+/// </summary>
+public sealed class ActorStopped : IActorTelemetryEvent
+{
+    public IActorRef Subject { get; }
+    public Type ActorType { get; }
+}
+
+/// <summary>
+/// Emitted when an actor restarts.
+/// </summary>
+public sealed class ActorRestarted : IActorTelemetryEvent
+{
+    public IActorRef Subject { get; }
+    public Type ActorType { get; }
+
+    public Exception Reason { get; }
+}
+```
+
+These events will be consumed from popular Akka.NET observability and management tools such as [Phobos](https://phobos.petabridge.com/) and [Petabridge.Cmd](https://cmd.petabridge.com/) to help provide users with more accurate insights into actor workloads over time, but you can also consume these events yourself by subscribing to them via the `EventStream`:
+
+```csharp
+// subscribe to all actor telemetry events
+Context.System.EventStream.Subscribe(Self, typeof(IActorTelemetryEvent));
+```
+
+**By default actor telemetry is disabled** - to enable it you'll need to turn it on via the following HOCON setting:
+
+```hocon
+akka.actor.telemetry.enabled = on
+```
+
+The performance impact of enabling telemetry is negligible, as you can [see via our benchmarks](https://github.com/akkadotnet/akka.net/pull/6294#issuecomment-1340251897).
+
+**Fixes and Updates**
+
+* [Akka.Streams: Fixed `System.NotSupportedException` when disposing stage with materialized `IAsyncEnumerable`](https://github.com/akkadotnet/akka.net/issues/6280)
+* [Akka.Streams: `ReuseLatest` stage to repeatedly emit the most recent value until a newer one is pushed](https://github.com/akkadotnet/akka.net/pull/6262)
+* [Akka.Remote: eliminate `ActorPath.ToSerializationFormat` UID allocations](https://github.com/akkadotnet/akka.net/pull/6195) - should provide a noticeable Akka.Remote performance improvement.
+* [Akka.Remote: Remoting and an exception as a payload message ](https://github.com/akkadotnet/akka.net/issues/3903) - `Exception` types are now serialized properly inside `Status.Failure` messages over the wire. `Status.Failure` and `Status.Success` messages are now managed by Protobuf - so you might see some deserialization errors while upgrading if those types are being exchanged over the wire.
+* [Akka.TestKit: `TestActorRef` can not catch exceptions on asynchronous methods](https://github.com/akkadotnet/akka.net/issues/6265)
+
+You can see the [full set of tracked issues for Akka.NET v1.4.47 here](https://github.com/akkadotnet/akka.net/issues?q=is%3Aclosed+milestone%3A1.4.47).
+
+| COMMITS | LOC+ | LOC- | AUTHOR |
+| --- | --- | --- | --- |
+| 10 | 2027 | 188 | Aaron Stannard |
+| 1 | 157 | 10 | Gregorius Soedharmo |
+
 #### 1.4.46 November 15th 2022 ####
 Akka.NET v1.4.46 is a security patch for Akka.NET v1.4.45 but also includes some other fixes.