CODEWITHSUNDEEP
springkotlinspring-webfluxproject-reactorchaining
Pedro Pepê
Pedro Pepê

Reputation: 123

Chaining multiple publishers transforming the responses

I want to chain one mono after each flux event. The mono publisher will need information from each event published by the flux. The response should be a flux with data of the flux event and the mono response.

After digging, I end up with a map inside a flatMap. The code looks like this:

override fun searchPets(petSearch: PetSearch): Flux<Pet> {
    return petRepository
        .searchPets(petSearch) // returns Flux<pet>
        .flatMap { pet -> 
            petService
            .getCollarForMyPet() // returns Mono<collar>
            .map { collar -> PetConverter.addCollarToPet(pet, collar) } //returns pet (now with with collar)
        }
}

My main concerns are:

Upvotes: 0

Views: 972

Answers (1)

Simon Basl&#233;
Simon Basl&#233;

Reputation: 28301

This approach is perfectly fine.

The Reactive Streams specification mandates that onNext events don't overlap, so there won't be an issue with race conditions.

flatMap introduces concurrency though, so multiple calls to the PetService will run in parallel. This shouldn't be an issue, unless searchPets emits some instance of Pet twice.

Not that due to that concurrency, flatMap can kind of reorder pets in this scenario. Imagine the search returns petA then petB, but the petService call for petA takes longer. In the ouptut of the flatMap, petB would be emitted first (with its collar set), then petA.

Upvotes: 1

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