What methods are used to manage the sequence of transactions in the Saga model?

In the Saga model, transaction sequence management is carried out using two main methods:

1. Choreography — each local transaction publishes events that other services listen to and initiate their transactions. There is no central coordinator, and the sequence of transactions is managed through events.

2. Orchestration — a centralized orchestrator manages the execution of each transaction by sending commands to services and waiting for their responses. The orchestrator controls the sequence and compensating actions in case of errors.

In Go, Saga can be implemented using channels and goroutines for asynchronous interaction, as well as contexts for canceling operations upon errors.

Example of simplified orchestration in Go:

func SagaOrchestrator(ctx context.Context) error {
    if err := Step1(ctx); err != nil {
        return err
    }
    if err := Step2(ctx); err != nil {
        compensateStep1(ctx)
        return err
    }
    if err := Step3(ctx); err != nil {
        compensateStep2(ctx)
        compensateStep1(ctx)
        return err
    }
    return nil
}

Here, each step is a local transaction, and in case of an error, compensating actions are called to rollback previous steps.