Akka.Streams.TestKit 1.4.21

• .NETStandard 2.0

  • Akka.Streams (>= 1.4.21)
  • Akka.TestKit (>= 1.4.21)

Maintenance Release for Akka.NET 1.4**
Akka.NET v1.4.21 is a significant release that includes major performance improvements, bug fixes, and a major update to the [Akka.DependencyInjection NuGet package](https://getakka.net/articles/actors/dependency-injection.html).
Performance Improvements**
Akka.NET v1.4.21 includes some major performance fixes and improvements:
[`Ask` is now ~10% faster](https://github.com/akkadotnet/akka.net/pull/5051)
[`MurmurHash` is 33% faster and allocates 0 memory](https://github.com/akkadotnet/akka.net/pull/5028) - used _heavily_ in DData, Cluster Sharding, and Consistent Hash Routers
`ActorPath.Parse` went from 1672 ns/op to 527 ns/op - a 68% improvement in throughput and a 50% reduction in memory. See [#5039](https://github.com/akkadotnet/akka.net/pull/5039) and [#5068](https://github.com/akkadotnet/akka.net/pull/5068).
[Akka.Remote: remove `ActorPath.ToString` call from `ResolveActorRefWithLocalAddress`](https://github.com/akkadotnet/akka.net/pull/5034)
Important**: [Revert `ThreadPool.SetMinThreads(0,0)`](https://github.com/akkadotnet/akka.net/pull/5059) - based on the input from users on "[Akka.NET v1.4.19: ChannelExecutor performance data](https://github.com/akkadotnet/akka.net/discussions/4983)"
Our observed performance numbers for Akka.Remote show a significant increase in performance for v1.4.21 over v1.4.20:
Before*
```
PS> dotnet run -c Release --framework netcoreapp3.1
OSVersion:                         Microsoft Windows NT 6.2.9200.0
ProcessorCount:                    16
ClockSpeed:                        0 MHZ
Actor Count:                       32
Messages sent/received per client: 200000  (2e5)
Is Server GC:                      True
Thread count:                      109
Num clients, Total [msg], Msgs/sec, Total [ms]
1,  200000,    113379,    1764.56
5, 1000000,    186429,    5364.05
10, 2000000,    185340,   10791.11
15, 3000000,    183218,   16374.06
20, 4000000,    179824,   22244.63
25, 5000000,    182716,   27365.89
30, 6000000,    182039,   32960.61
```
After*
```
PS> dotnet run -c Release --framework netcoreapp3.1
OSVersion:                         Microsoft Windows NT 6.2.9200.0
ProcessorCount:                    16
ClockSpeed:                        0 MHZ
Actor Count:                       32
Messages sent/received per client: 200000  (2e5)
Is Server GC:                      True
Thread count:                      111
Num clients, Total [msg], Msgs/sec, Total [ms]
1,  200000,    109770,    1822.14
5, 1000000,    192902,    5184.79
10, 2000000,    191663,   10435.53
15, 3000000,    191339,   15679.11
20, 4000000,    192725,   20755.78
25, 5000000,    189754,   26350.14
30, 6000000,    189772,   31617.20
```
> N.B. these after numbers don't benefit from the performance benefits we observed in v1.4.20 when we invoked `ThreadPool.SetMinThreads(0,0)`, which makes them even more impressive.
Akka.DependencyInjection Updates**
We had one major issue we implemented in v1.4.21 for Akka.DependencyInjection: [Abstraction of `ServiceProvider`, Improving Akka.DependencyInjection ](https://github.com/akkadotnet/akka.net/pull/4814)
What this change did was:
Deprecate the `Akka.DependencyInjection.ServiceProvider` class in favor of the `Akka.DependencyInjection.DependencyResolver` class - to avoid namespace collision with Microsoft.Extensions.DependencyInjection.ServiceProvider;
Deprecates the `Akka.DependencyInjection.ServiceProviderSetup` class in favor of the `Akka.DependencyInjection.DependencyResolverSetup` class for consistency reasons;
`Akka.DependencyInjection.DependencyResolver` now takes an input of type [`IDependencyResolver`](https://getakka.net/api/Akka.DependencyInjection.IDependencyResolver.html), which allows users to abstract away the `IServiceProvider` and mock / replace it during unit testing; and
Added some non-generic `Props` methods for dynamically spawning actors via DI.
All of these changes are backwards-compatible with v1.4.20 and earlier - and the deprecation warnings will appear in your code when you upgrade. If you run into any [issues upgrading to Akka.DependencyInjection v1.4.21 please reply on this thread](https://github.com/akkadotnet/akka.net/discussions/5070)!
Other Changes and Fixes**
[Akka.Streams: A couple of fixes affecting the `FileSubscriber`](https://github.com/akkadotnet/akka.net/pull/5035)
[Akka.DistributedData: memory leak when recovering events from LMDB data store](https://github.com/akkadotnet/akka.net/issues/5022)
[Akka.DistributedData: port `VectorClock` performance optimizations to `VersionVector` and similar types](https://github.com/akkadotnet/akka.net/issues/4956)
To see the [full set of fixes in Akka.NET v1.4.21, please see the milestone on Github](https://github.com/akkadotnet/akka.net/milestone/51).
| COMMITS | LOC+ | LOC- | AUTHOR |
| --- | --- | --- | --- |
| 5 | 34 | 24 | Aaron Stannard |
| 4 | 196 | 77 | Gregorius Soedharmo |
| 3 | 3 | 3 | dependabot[bot] |
| 1 | 2 | 2 | Wessel Kranenborg |
| 1 | 1 | 1 | Martijn Schoemaker |