Event Store: Idempotency problmem

[Ricardo Enes da Silva]

Given 1 Handler subscribed to 2 streams and publishing the same event twice to both streams

I get the following

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. But would expect 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. Curiously If a change publishing order I get 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

So it appear s idempotency is only working on the first stream created

This is my code

 class Program

    {

        static void Main(string[] args)

        {

            var connection = EventStoreConnection.Create(new Uri("tcp://admin:chan...@127.0.0.1:1113"));

            connection.ConnectAsync().Wait();

            var settings = PersistentSubscriptionSettings

                .Create()

                .StartFromCurrent()

                .WithMessageTimeoutOf(new TimeSpan(100));

            try {

                connection.CreatePersistentSubscriptionAsync(

                    "stream", "group",

                    settings, new UserCredentials("admin", "changeit")

                ).Wait();

            } catch{ }

            try {

                connection.CreatePersistentSubscriptionAsync(

                    "stream2", "group",

                    settings, new UserCredentials("admin", "changeit")

                ).Wait();

            } catch{ }

            var event1 = new EventData(Guid.NewGuid(),"event", false,Encoding.UTF8.GetBytes("Event 1"),null);

            new Handler(connection);

            connection.AppendToStreamAsync("stream", ExpectedVersion.Any, event1);

            connection.AppendToStreamAsync("stream", ExpectedVersion.Any, event1);

            connection.AppendToStreamAsync("stream2", ExpectedVersion.Any, event1);

            connection.AppendToStreamAsync("stream2", ExpectedVersion.Any, event1);

            Console.ReadKey();

        }

    }

    class Handler

    {

        public Handler(IEventStoreConnection connection) {

            connection.ConnectToPersistentSubscription(

                "stream", "group", 

                Handle, (s, r, e) => {}, new UserCredentials("admin", "changeit"), 

                1, false

            );

            

            connection.ConnectToPersistentSubscription(

                "stream2", "group", 

                Handle, (s, r, e) => {}, new UserCredentials("admin", "changeit"), 

                1, false

            );

        }

        void Handle(EventStorePersistentSubscriptionBase subscription, ResolvedEvent @event) {

            Console.WriteLine($"Handler Received: Id '{@event.Event.EventId}' On Stream: '{@event.Event.EventStreamId}' ");

            subscription.Acknowledge(@event);

        }

    }

Thank you 

[Greg Young]

Idempotent writes are per stream.

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Studying for the Turing test

[Ricardo Enes da Silva]

Yes  that's what I thought and therefore don't expect that handlers be called twice for the same message posted to different streams 

-Event id cc81832b-60c5-4813-add5-aacb2b7aef7c was published twice to 'stream'  then twice to 'stream2'

-Handler receives event once on  'stream', which is what I expect 

-But twice on 'stream2',

If I pulish to 'stream2' first the opposite happens

-Handler receives event once on  'stream2', which is what I expect 
-But twice on 'stream',

Its as though idempotency is only observed for the first stream published to.

BTW I am using the .NET client to connect to Event Store

On Thursday, 19 November 2015 06:19:56 UTC, Ricardo Enes da Silva wrote:

Given 1 Handler subscribed to 2 streams and publishing the same event twice to both streams

I get the following

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. But would expect 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. Curiously If a change publishing order I get 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

So it appear s idempotency is only working on the first stream created

This is my code

 class Program

    {

        static void Main(string[] args)

        {

            var connection = EventStoreConnection.Create(new Uri("tcp://admin:changeit@127.0.0.1:1113"));

Thank you 

[Greg Young]

"ExpectedVersion.Any"

Try using expected version and it will work fine.

What is happening is you are only using the "try best you can cache"
which is by eventid. Duplicate event ids between streams is an edge
condition (event id can only be in the cache once). The bigger
question is why are you writing events with the same id to multiple
streams.

Greg

>> Uri("tcp://admin:chan...@127.0.0.1:1113"));

[Ricardo Enes da Silva]

Thanks Greg !

I guess what I was trying to do is what i think you previously may have mentioned of using projections but was thinking I could do it from the client.e.g. Publish event to TypeStream and CorrelationIdStream. I am guessing this is not the correct approach and that I should only publish to a single stream and rely on projections to republish it to. Is that correctand what should the base stream be, TypeStream ?

Thanks

On Thursday, 19 November 2015 06:19:56 UTC, Ricardo Enes da Silva wrote:

Given 1 Handler subscribed to 2 streams and publishing the same event twice to both streams

I get the following

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. But would expect 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

.. Curiously If a change publishing order I get 

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream2'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

Handler Received: Id 'cc81832b-60c5-4813-add5-aacb2b7aef7c' On Stream: 'stream'

So it appear s idempotency is only working on the first stream created

This is my code

 class Program

    {

        static void Main(string[] args)

        {

            var connection = EventStoreConnection.Create(new Uri("tcp://admin:changeit@127.0.0.1:1113"));

Thank you