Micronaut: mixing @transaction with gRPC Endpoint methods

CreateProposalEndpoint.kt

@Singleton
open class CreateProposalEndpoint(@Inject val repository: ProposalRespository) : ProposalGrpcServiceGrpc.ProposalGrpcServiceImplBase() {

    @Transactional // starts the current transaction
    open override fun create(request: CreateProposalRequest, responseObserver: StreamObserver<CreateProposalResponse>) {

        val proposal = repository.save(request.toModel()) // with Hibernate, the INSERT may not be flushed here

        // returns to the client without waiting for the commit
        responseObserver.onNext(CreateProposalResponse.newBuilder().build())
        responseObserver.onCompleted()
      
    } // WARNING: the current transaction is only commited (and flushed) here
}

Some interesting articles about Reactive Transaction Management with Spring Boot:

• Reactive Transactions with Spring
• StackOverflow: Does Spring Transaction Management Work with Spring WebFlux?
  
• StackOverflow: Transaction handling when wrapping Stream into Flux
• StackOverflow: Transaction rollback in a reactive application

GitHub Issue #187 - Transactional methods close before transaction is commited

https://stackoverflow.com/questions/64136645/is-it-possible-to-use-transactional-and-kotlin-coroutines-in-spring-boot

Micronaut Data Transactions with R2DBC