CorrelationId is not included when publish from/to Saga

Question

Im using MassTransit Sagas. It starts when an incoming event(AccountCreatedInWebAppEvent) does some processing and will then publish another event (SagaAccountCreatedEvent)

I have a consumer that listens to SagaAccountCreatedEvent, but in the consumer the context.CorrelationId is null if I dont set it explicitly as in the example below (return new SagaAccountCreatedEvent() {...}). Shoulnt the correlationId be included without me having to insert it into the message, by the Saga-magic? (the same goes for publishing from a consumer to Saga-"handler")

InstanceState(i => i.CurrentState);
Event(() => AccountCreatedInWebAppEvent, e => e.CorrelateBy<int>(sagaState => sagaState.AccountId, context => context.Message.Account.AccountId)
                                                .SelectId(context => Guid.NewGuid()))

...

Initially(
    When(AccountCreatedInWebAppEvent)
        .Then(context =>
        {
            context.Instance.AccountId = context.Data.Account.AccountId;
            context.Instance.CreatedInWebApp = DateTime.Now; 
        })
        .TransitionTo(AccountCreatedSentOut)
        .Publish(context =>
        {
            return new SagaAccountCreatedEvent() { Account = context.Data.Account, CorrelationId = context.CorrelationId.Value };
        })

Consumer method

public async Task Consume(ConsumeContext context) {

//here context.correlationId is null

}

Chris Patterson Chris Patterson · Accepted Answer · 2019-11-07T13:35:49

Since your initial event is correlated by an int property, you are initializing the instance with SelectId(x => Guid.NewGuid()). To get that value when you publish the subsequent event, you should use context.Instance.CorrelationId as shown:

.Publish(context =>
    new SagaAccountCreatedEvent() 
    {
        Account = context.Data.Account,
        CorrelationId = context.Instance.CorrelationId
    })

The value you were using, context.CorrelationId is from the saga's consume context and is only present for events that are directly correlated by Guid using the CorrelationId.

CorrelationId is not included when publish from/to Saga

1 Answers