how to interupt chain operation

[Archsx]

I'm using Kotlin and Quarkus to building restful api , I wanna know how to interrupt the chain operation when there is some error.
say we have code below:

fun asyncOperation1(): Uni<String> {}

fun asyncOperation2(): Uni<String> {}

fun asyncOperation3(): Uni<String> {}

@POST
@Path("/somepath")
@ReactiveTransactional
fun m1(payload: Payload): Uni<MyResponse<String>> {
    val uniRes1 = asyncOperation1()
    val uniRes2 = asyncOperation2()
    val uniRes3 = asyncOperation3()

    return Uni.combine().all().unis(uniRes1, uniRes2, uniRes3).combinedWith { str1, str2, str3 ->
        val arr = listOf(str1, str2, str3)
        for (item in arr) {
            if(item == "invalid string"){
                return Uni.createFrom().failure("Invalid String")
                // throw Exception()
            }
        }
        arr
    }.chain { arr -> 
       // ...
    }.onFailure {
        return Uni.createFrom().Item(Myresponse.error("invalid"))
    }
    .chain{} // further operaion
    .chain{
         return Uni.createFrom().Item(Myresponse.Ok("Success"))
     }
}

the code is for demostration. Here I have three async operation , and I wanna check if any of the results is "invalid string", if any I'd prefer stop the chain operaion immediately and return the HttpResponse to frontend(return at the OnFailure method and no more further operation).if there is not, then pass the list of results to the further operation.

the docs says we could create failed Uni instances with Uni.createFrom().failure(new Exception("boom")), could I just throw a runtimeExcepition?

is the code above the right way to handle the error in Mutiny?

[jponge]

Returning a failed Uni is indeed the correct way. Internally we catch some exceptions from lambdas so it might work sometimes, but this is not the proper way.

You might also look at https://smallrye.io/smallrye-mutiny/2.5.3/guides/joining-unis/ and the fail-fast option.

[Archsx]

Hi, I've tried to return a failed Uni but it didn't work .

fun main(args: Array<String>) {
    val uni1 = Uni.createFrom().item(Random.nextInt(0, 6))
    val uni2 = Uni.createFrom().item(Random.nextInt(0, 6))
    val uni3 = Uni.createFrom().item(Random.nextInt(0, 6))

    Uni.combine()
        .all()
        .unis(uni1, uni2, uni3)
        .combinedWith { res1, res2, res3 ->
            if (res2 < 2) {
                return@combinedWith Uni.createFrom()
                    .failure<RuntimeException>(RuntimeException("less than 2"))
            }
            res1 + res2 + res3
        } // Uni<Any!>! 
        .onFailure()
        .recoverWithUni(Uni.createFrom().item(1000))
        //        .recoverWithItem(1000)
        .map { total -> (total as Int) + 1 }
        .map { total -> total + 2 }
        .subscribe()
        .with(System.out::println)
}

it is interesting that it seems to lose type when I return a failure in combinedWith, as you can see, the IDEA shows the result of combinedWith is Uni<Any!>!, but not Uni<Int>

and when failure occurs, both recoverWithUni and recoverWithItem didn't recover it , I got error

Exception received by: io.smallrye.mutiny.infrastructure.Infrastructure.handleDroppedException(Infrastructure.java:295)
java.lang.ClassCastException: class io.smallrye.mutiny.operators.uni.builders.UniCreateFromKnownFailure cannot be cast to class java.lang.Integer (io.smallrye.mutiny.operators.uni.builders.UniCreateFromKnownFailure is in unnamed module of loader 'app'; java.lang.Integer is in module java.base of loader 'bootstrap')

[jponge]

Would you mind trying join()?