Backport of the feature called ClusterDistribution in Lagom #4455

ismaelhamed · 2020-06-07T17:26:24Z

This is a feature backported from Lagom which essentially works like a sharded singleton. A number of actor instances are kept alive and balanced across the cluster.
The main motivation to bring it into Akka is the use case where workers that update projections. By tagging akka-persistence events with N different tags and then running N workers, one for each tag which consumes that partition of the events and updates a projection.

This feature was implemented in Akka typed, not yet available in Akka.NET. But given that users will either borrow Lagom's implementation anyway or roll their own, IMO it's worthwhile having this on classical Akka.

Implementation
Unit tests
Multinode tests

Aaronontheweb · 2020-06-08T14:33:43Z

@ismaelhamed we should add some documentation for this feature too - honestly that'll help me review it. We were just looking at akka-projections in the Gitter chat room the other day too. Seems like a useful feature in the long run.

ismaelhamed · 2020-06-08T18:03:48Z

@Aaronontheweb this is pretty much the only documentation you'll find, and is already included in this PR. But because this feature was borrowed from Lagom, you could also read its documentation for a little more of background (though this implementation is way more straightforward).

Actually, the recommended way to distribute the projections in akka-projections is by leveraging this new ShardedDaemonProcess.

ismaelhamed · 2020-06-11T12:39:00Z

src/contrib/cluster/Akka.Cluster.Sharding/reference.conf

+  # `role` setting limit what nodes the daemon processes and the keep alive pingers will run on.
+  # Some settings can not be changed (remember-entitites and related settings, passivation, number-of-shards),
+  # overriding those settings will be ignored.
+  sharding = ${akka.cluster.sharding}


This seems to work, but akka.cluster.sharding.coordinator-singleton = ${akka.cluster.singleton} does not. I guess the current hocon implementation cannot load a config section from another file!?

I don't think so - cc @Arkatufus

ismaelhamed · 2020-06-14T18:12:33Z

src/contrib/cluster/Akka.Cluster.Sharding.Tests.MultiNode/ShardedDaemonProcessSpec.cs

+        public void ShardedDaemonProcess_Should_Init_Actor_Set()
+        {
+            // HACK
+            RunOn(() => FormCluster(_config.First, _config.Second, _config.Third), _config.First);


Test does not pass unless I put FormCluster() inside a RunOn(). I'm missing something.

I'll take a look during review

Not sure, off the top of my head, what the issue might be here - what type of error do you get?

I only get one ProcessActorEvent instead of the 4 expected (one per ProcessActor), so the test fails with timeout.

Aaronontheweb

Have some minor changes requested here

Aaronontheweb · 2020-06-16T14:06:00Z

src/core/Akka.API.Tests/CoreAPISpec.ApproveClusterSharding.approved.txt

@@ -190,7 +190,7 @@ namespace Akka.Cluster.Sharding
            public override bool Equals(object obj) { }
            public override int GetHashCode() { }
        }
-        public sealed class StartEntityAck : Akka.Cluster.Sharding.IClusterShardingSerializable
+        public sealed class StartEntityAck : Akka.Cluster.Sharding.IClusterShardingSerializable, Akka.Event.IDeadLetterSuppression


Aaronontheweb · 2020-06-16T14:07:51Z

src/contrib/cluster/Akka.Cluster.Sharding.Tests.MultiNode/ShardedDaemonProcessSpec.cs

+        public void ShardedDaemonProcess_Should_Init_Actor_Set()
+        {
+            // HACK
+            RunOn(() => FormCluster(_config.First, _config.Second, _config.Third), _config.First);


Not sure, off the top of my head, what the issue might be here - what type of error do you get?

Aaronontheweb · 2020-06-16T14:08:31Z

docs/articles/clustering/cluster-sharded-daemon-process.md

+To set up a set of actors running with Sharded Daemon process each node in the cluster needs to run the same initialization
+when starting up:
+
+```csharp


Use a DocFx snippet here: https://dotnet.github.io/docfx/spec/docfx_flavored_markdown.html#code-snippet

docs/articles/clustering/cluster-sharded-daemon-process.md

Aaronontheweb

LGTM

Aaronontheweb · 2020-06-17T01:05:03Z

Is there a reason why I can't update this PR myself? I don't see an "Update Branch" button :\

ismaelhamed · 2020-06-17T06:35:07Z

"Allow edits by maintainers" was unchecked. Is this option unchecked now by default?

Aaronontheweb · 2020-06-17T14:13:13Z

@ismaelhamed maybe - I'll need to check!

ismaelhamed force-pushed the sharded-daemon branch 2 times, most recently from a44ef10 to 43093ab Compare June 8, 2020 11:33

ismaelhamed force-pushed the sharded-daemon branch from 43093ab to 7d2fa7a Compare June 11, 2020 12:32

ismaelhamed commented Jun 11, 2020

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ismaelhamed force-pushed the sharded-daemon branch from 7d2fa7a to b77903e Compare June 14, 2020 18:10

ismaelhamed commented Jun 14, 2020

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ismaelhamed marked this pull request as ready for review June 14, 2020 18:13

ismaelhamed changed the title ~~[WIP] Backport of the feature called ClusterDistribution in Lagom~~ Backport of the feature called ClusterDistribution in Lagom Jun 14, 2020

ismaelhamed force-pushed the sharded-daemon branch from b77903e to 0f1a862 Compare June 14, 2020 18:14

Aaronontheweb self-requested a review June 15, 2020 21:12

Aaronontheweb requested changes Jun 16, 2020

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ismaelhamed force-pushed the sharded-daemon branch from 0f1a862 to 358b83f Compare June 16, 2020 15:41

ismaelhamed requested a review from Aaronontheweb June 16, 2020 15:42

Aaronontheweb approved these changes Jun 17, 2020

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Backport of the feature called ClusterDistribution in Lagom

b77ee9e

ismaelhamed force-pushed the sharded-daemon branch from 358b83f to b77ee9e Compare June 17, 2020 06:40

Aaronontheweb merged commit 5e559f7 into akkadotnet:dev Jun 17, 2020

Aaronontheweb added this to the 1.4.8 milestone Jun 17, 2020

This was referenced Jun 17, 2020

added v1.4.8 release notes #4478

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Backport of the feature called ClusterDistribution in Lagom #4455

Backport of the feature called ClusterDistribution in Lagom #4455

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Backport of the feature called ClusterDistribution in Lagom #4455

Backport of the feature called ClusterDistribution in Lagom #4455

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