Question 121302 in Redis Question posted in
The official documentation can be found here.

Redis – MassTransit StateMachine correlation by Int

New to Masstransit here and I wanted to correlate my message with an int value (let’s call it OrderId of type INT. I will use the same order management example from Masstransit).

I wanted to see if anyone was able to use an int to correlate events and messages in Masstransit.

I used this code in my events (both the events)

x.CorrelateById<int>(state => state.OrderId, context => context.Message.OrderId)

This compiles fine but then throws and exception

NotImplementedByDesignException. Masstransit doc says : "Redis only supports event correlation by CorrelationId, it does not support queries. If a saga uses expression-based correlation, a NotImplementedByDesignException will be thrown."

I am using CorrelateById() so not sure why I am seeing this exception. I don’t see any query here (or is it this func that returns the OrderId? The correlationId has a similar expression although it takes only one argument of type: Func<ConsumeContext<TMessage>, Guid> selector)

All I want is to be able to correlate message and event by an Int prop coming to my first event of the state machine. (That I have no control over by the way).

I feel creating another GUID just for Masstransit and link it to that OrderId is not the best option here.

My other question: is there any out of the box way in MassTransit to get the all event data for a specific CorrelationId (event sourcing style). I saw there was a MassTransit.EventStoreIntegration repo on github but since we can get the last version of the state instance I thought there would be a way to see all state instances/ or messages being persisted then pulled.

Sure I can see that in the log but I would like to see only the state changes that were pushed.

Thanks

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2

Answers


  1. Chosen as BEST ANSWER
    0

    As per @Chris answer, and because I wanted to use an INT property and still use redis, I used Guid CorrelationId that was generated from that INT value with padded zeros.

    CorrelationId = new Guid(OrderIdIntValue.ToString().PadLeft(32, '0'))

    I am aware of the Guid vs int discussion in distributed systems. For my case this works with no issues since that Int value is generated by a unique source of truth (that I consume and don't have control over).


  2. 0

    Correlation by anything other than the Guid CorrelationId property is a query. And, as you’ve found out, Redis doesn’t support queries. If you need to correlate events using a type other than a Guid, Redis is not an option.

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