SagaInterceptor

Interceptor for saga step execution, enabling pre/post-step hooks with veto capability.

Interceptors allow cross-cutting concerns (logging, metrics, authorization, audit logging) to run before and after every saga step and can veto a step before its side effect fires.

Functional Interface

This is a functional interface (SAM — Single Abstract Method), which means you can use lambda expressions to create interceptors:

val auditInterceptor = SagaInterceptor<OrderContext, OrderResult, Unit> { phase ->
    when (phase) {
        is StepPhase.Before -> {
            auditLog.append("About to execute: ${phase.step.stringValue}")
            InterceptorOutcome.Continue
        }
        is StepPhase.After -> {
            auditLog.append("Completed: ${phase.step.stringValue}")
            InterceptorOutcome.Continue
        }
        is StepPhase.Compensation -> {
            auditLog.append("Compensated: ${phase.step.stringValue}")
            InterceptorOutcome.Continue
        }
    }
}

Veto Semantics

Returning InterceptorOutcome.Veto from a Before phase aborts the step and initiates compensation of all prior completed steps. The veto reason is carried in SagaExecutionError.

Ordering

For multiple interceptors A, B, C registered in order:

• Before is called A → B → C

• After is called C → B → A (LIFO, mirrors compensation semantics)

Parameters