Akka 1.5.57

• .NETStandard 2.0

  • Akka.Analyzers (>= 0.3.3)
  • Microsoft.Extensions.ObjectPool (>= 6.0.36)
  • Newtonsoft.Json (>= 13.0.1)
  • System.Collections.Immutable (>= 6.0.1)
  • System.Configuration.ConfigurationManager (>= 6.0.1)
  • System.Reflection.Emit (>= 4.7.0)
  • System.Threading.Channels (>= 6.0.0)

• net6.0

  • Akka.Analyzers (>= 0.3.3)
  • Microsoft.Extensions.ObjectPool (>= 6.0.36)
  • Newtonsoft.Json (>= 13.0.1)
  • System.Collections.Immutable (>= 6.0.1)
  • System.Configuration.ConfigurationManager (>= 6.0.1)

Akka.NET v1.5.57 is a minor release containing significant new features for Akka.Persistence and structured/semantic logging.

**Akka.Persistence Completion Callbacks and Async Handler Support**

* [Persistence completion callbacks via Defer - simplified alternative](https://github.com/akkadotnet/akka.net/pull/7957) - This release adds completion callback and async handler support to `Persist`, `PersistAsync`, `PersistAll`, and `PersistAllAsync` methods in Akka.Persistence. Key improvements include:
   - **Async Handler Support**: All persist methods now support `Func<TEvent, Task>` handlers for async event processing
   - **Completion Callbacks**: `PersistAll` and `PersistAllAsync` now accept optional completion callbacks (both sync `Action` and async `Func<Task>`) that execute after all events are persisted and handled
   - **Ordering Guarantees**: Completion callbacks use `Defer`/`DeferAsync` internally to maintain strict ordering guarantees
   - **Zero Breaking Changes**: All new APIs are additive overloads

**Persistence Code Examples:**

```csharp
// Async handler support - process events asynchronously
Persist(new OrderPlaced(orderId), async evt =>
{
   await _orderService.ProcessOrderAsync(evt);
});

// PersistAll with completion callback - know when all events are done
PersistAll(orderEvents, evt =>
{
   _state.Apply(evt);
}, onComplete: () =>
{
   // All events persisted and handlers executed
   _logger.Info("Order batch completed");
   Sender.Tell(new BatchComplete());
});

// PersistAll with async handler AND async completion callback
PersistAll(events,
   handler: async evt => await ProcessEventAsync(evt),
   onCompleteAsync: async () =>
   {
       await NotifyCompletionAsync();
       Sender.Tell(Done.Instance);
   });

// PersistAllAsync with completion - allows commands between handlers
PersistAllAsync(largeEventBatch,
   handler: evt => _state.Apply(evt),
   onComplete: () => Sender.Tell(new BatchProcessed()));
```

The implementation maintains Akka.Persistence's strict ordering guarantees by using `Defer`/`DeferAsync` for completion callbacks, ensuring they execute in order even when called with empty event collections. The new async handler invocations (`IAsyncHandlerInvocation`) are processed via `RunTask` to preserve the actor's single-threaded execution model.

**Native Semantic Logging Support**

* [Add native semantic logging support with property extraction](https://github.com/akkadotnet/akka.net/pull/7955) - Fixes [issue #7932](https://github.com/akkadotnet/akka.net/issues/7932). This release adds comprehensive structured logging support to Akka.NET with both positional (`{0}`) and named (`{PropertyName}`) message template parsing, enabling seamless integration with modern logging frameworks like Serilog, NLog, and Microsoft.Extensions.Logging. Key capabilities include:
   - New `LogMessage.PropertyNames` and `GetProperties()` APIs for property extraction
   - `SemanticLogMessageFormatter` as the new default formatter
   - Performance optimized with 75% allocation reduction compared to the previous implementation
   - Zero new dependencies and fully backward compatible
   - EventFilter support for semantic templates in unit tests

1 contributor since release 1.5.56

| COMMITS | LOC+ | LOC- | AUTHOR         |
|---------|------|------|----------------|
| 2       | 3703 | 81   | Aaron Stannard |

To see the full set of changes in Akka.NET v1.5.57, click here:
* [1.5.57-beta1 milestone](https://github.com/akkadotnet/akka.net/milestone/140?closed=1)
* [1.5.57-beta2 milestone](https://github.com/akkadotnet/akka.net/milestone/141?closed=1)