Akka.NET v1.5 Plans and Goals

Beginning with our March 9th, 2022 Akka.NET Community Standup we've shared our plans for the roadmap of Akka.NET v1.5.

While not every technical detail is finalized yet, we do want to share the goals and some of the specific plans of what's included in this next minor version release of Akka.NET!

Goals

Based on feedback from Akka.NET users, here are the top priorities:

  1. Better documentation and examples - after simplifying the Akka.NET APIs around configuration and startup, modernizing all samples and deployment guidance is the biggest issue affecting end-users.
  2. Improved Akka.Remote + Cluster.Sharding performance - we want to go from ~350,000 msg/s to 1m+ msg/s in our RemotePingPong benchmark by changing the design of Akka.Remote's actors and optionally, replacing our transports.
  3. Improved default serialization options - Newtonsoft.Json sucks. Full stop.
  4. Improved Akka.Cluster formation experience - in layman's terms this means releasing Akka.Management out of beta and incorporating it into the Akka.Cluster literature and code samples.
  5. Leveraging .NET 6+ primitives for improved performance - thread execution, zero-allocation System.Memory data structures, and more.
  6. Make CQRS a priority in Akka.Persistence - tags are an especially weak area for Akka.Persistence right now, given that they require table scans.
  7. Leverage Microsoft.Extensions more closely - consume Microsoft.Extensions.Configuration from HOCON, allow Microsoft.Extensions.Logging interplay, and more.
  8. Cleanup - there are a lot of old constructs and that can be removed from Akka.NET.

How to Contribute

Contributing to the v1.5 effort is somewhat different than our normal maintenance contributions to Akka.NET,in the following ways:

  1. Breaking binary compatibility changes are allowed so long as they are cost-justified - contributors must be able to explain both the benefits and trade-offs involved in making this change in order for it to be accepted;
  2. Wire compatibility must include a viable upgrade path - if we're to introduce changes to the wire format of Akka.NET, contributors must demonstrate and document a viable upgrade path for end-users; and
  3. Bigger bets are encouraged - now is a good time to take some risks on the code base. So long as contributors can offer sound arguments for taking those bets (and this includes acknowledging and being realistic about trade-offs) then they should feel free to propose new changes that align with the 1.5 goals.

Good Areas for Contribution

  1. .NET 6 dual-targeting - there will be lots of areas where we can take advantage of new .NET 6 APIs for improved performance;
  2. Performance optimization - performance optimization around Akka.Remote, Akka.Persistence, Akka.Cluster.Sharding, DData, and core Akka will be prioritized in this release and there are many areas for improvement;
  3. Akka.Hosting - there are lots of extension points and possibilities for making the APIs as expressive + concise as possible - we will need input from contributors to help make this possible;
  4. API Cleanup - there are lots of utility classes or deprecated APIs that can be deleted from the code base with minimal impact. Less is more; and
  5. New ideas and possibilities - this is a great time to consider adding new features to Akka.NET. Be bold.
Important

Familiarize yourself with our Akka.NET contribution guidelines for best experience.

Designs & Major Changes

Akka.Cluster.Sharding State Storage

One of the most significant upgrades we've made in Akka.NET v1.5 is a complete rewrite of Akka.Cluster.Sharding's state storage system.

Note

You can watch our discussion of this Akka.Cluster.Sharding upgrade during our September, 2022 Akka.NET Community Standup for more details.

In Akka.NET v1.5 we've split Akka.Cluster.Sharding's state-store-mode into two parts:

  • CoordinatorStore (akka.cluster.sharding.state-store-mode) and
  • ShardStore (akka.cluster.sharding.remember-entities-store.)

Which can use different persistence modes configured via akka.cluster.sharding.state-store-mode & akka.cluster.sharding.remember-entities-store.

Important

The goal behind this split was to remove the ShardCoordinator as a single point of bottleneck during remember-entities=on recovery - in Akka.NET v1.4 all remember-entity state is concentrated in the journal of the PersistentShardCoordinator or the CRDT used by the DDataCoordinator. In v1.5 the responsibility for remembering entities has been pushed to the Shard actors themselves, which allows for remembered-entities to be recovered in parallel for all shards.

Possible combinations:

state-store-mode remember-entities-store CoordinatorStore mode ShardStore mode
persistence (default) - (ignored) persistence persistence
ddata ddata ddata ddata
ddata eventsourced (new) ddata persistence

There should be no breaking changes from user perspective. Only some internal messages/objects were moved. There should be no change in the PersistentId behavior and default persistent configuration (akka.cluster.sharding.state-store-mode)

This change is designed to speed up the performance of Akka.Cluster.Sharding coordinator recovery by moving remember-entities recovery into separate actors - this also solves major performance problems with the ddata recovery mode overall.

The recommended settings for maximum ease-of-use for Akka.Cluster.Sharding in new applications going forward will be:

akka.cluster.sharding{
  state-store-mode = ddata
  remember-entities-store = eventsourced
}

However, for the sake of backwards compatibility the Akka.Cluster.Sharding defaults have been left as-is:

akka.cluster.sharding{
  state-store-mode = persistence
  # remember-entities-store (not set - also uses legacy Akka.Persistence)
}
Important

Read "Upgrading to Akka.NET V1.5 - Cluster.Sharding" for details on how to upgrade from Akka.NET v1.5.

Akka.Hosting

We want to make Akka.NET something that can be instantiated more typically per the patterns often used with the Microsoft.Extensions.Hosting APIs that are common throughout .NET.

using Akka.Hosting;
using Akka.Actor;
using Akka.Actor.Dsl;
using Akka.Cluster.Hosting;
using Akka.Remote.Hosting;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAkka("MyActorSystem", configurationBuilder =>
{
    configurationBuilder
        .WithRemoting("localhost", 8110)
        .WithClustering(new ClusterOptions(){ Roles = new[]{ "myRole" }, 
            SeedNodes = new[]{ Address.Parse("akka.tcp://[email protected]:8110")}})
        .WithActors((system, registry) =>
    {
        var echo = system.ActorOf(act =>
        {
            act.ReceiveAny((o, context) =>
            {
                context.Sender.Tell($"{context.Self} rcv {o}");
            });
        }, "echo");
        registry.TryRegister<Echo>(echo); // register for DI
    });
});

var app = builder.Build();

app.MapGet("/", async (context) =>
{
    var echo = context.RequestServices.GetRequiredService<ActorRegistry>().Get<Echo>();
    var body = await echo.Ask<string>(context.TraceIdentifier, context.RequestAborted).ConfigureAwait(false);
    await context.Response.WriteAsync(body);
});

app.Run();

No HOCON. Automatically runs all Akka.NET application lifecycle best practices behind the scene. Automatically binds the ActorSystem and the ActorRegistry, another new 1.5 feature, to the IServiceCollection so they can be safely consumed via both actors and non-Akka.NET parts of users' .NET applications.

This should be open to extension in other child plugins, such as Akka.Persistence.SqlServer:

builder.Services.AddAkka("MyActorSystem", configurationBuilder =>
{
    configurationBuilder
        .WithRemoting("localhost", 8110)
        .WithClustering(new ClusterOptions()
        {
            Roles = new[] { "myRole" },
            SeedNodes = new[] { Address.Parse("akka.tcp://[email protected]:8110") }
        })
        .WithSqlServerPersistence(builder.Configuration.GetConnectionString("sqlServerLocal"))
        .WithShardRegion<UserActionsEntity>("userActions", s => UserActionsEntity.Props(s),
            new UserMessageExtractor(),
            new ShardOptions(){ StateStoreMode = StateStoreMode.DData, Role = "myRole"})
        .WithActors((system, registry) =>
        {
            var userActionsShard = registry.Get<UserActionsEntity>();
            var indexer = system.ActorOf(Props.Create(() => new Indexer(userActionsShard)), "index");
            registry.TryRegister<Index>(indexer); // register for DI
        });
})

ActorRegistry

As part of Akka.Hosting, we need to provide a means of making it easy to pass around top-level IActorRefs via dependency injection both within the ActorSystem and outside of it.

The ActorRegistry will fulfill this role through a set of generic, typed methods that make storage and retrieval of long-lived IActorRefs easy and coherent:

var registry = ActorRegistry.For(myActorSystem); // fetch from ActorSystem
registry.TryRegister<Index>(indexer); // register for DI
registry.Get<Index>(); // use in DI