io.smallrye.mutiny.Uni 多线程不起作用 (Quarkus)

Question

I try to perform 2 different operations with different threads each.Here is my code :

 Uni.combine().all()
            .unis(getItem(), getItemDetails())
            .asTuple().subscribe().with(tuple -> {
                context.setItem(tuple.getItem1());
                context.setItemDetails(tuple.getItem2());
            });

Methods :

public Uni<ItemResponse> callGetItem(){
    Supplier<ItemResponse> supplier = () -> itemService.getItem("item_id_1");
    return Uni.createFrom().item(supplier);
}

public Uni<ItemDetailsResponse> callGetItemDetail(){
        Supplier<ItemDetailsResponse> supplier = () -> itemService.getItemDetail("dummy_item_id");
        return Uni.createFrom().item(supplier) ;
    }

But when i run the code both callGetItem() and callGetItemDetail() methods works in the same thread (executor-thread-0).

Where am i doing wrong?

Edit:

When i give an executor service Executors.newFixedThreadPool(2) for my Unis, They still work in single thread. I mofified callGetItem() and callGetItemDetail() as :

 public Uni<ItemResponse> callGetItem(){
    Supplier<ItemResponse> supplier = () -> itemService.getItem("item_id_1");
    return Uni.createFrom().item(supplier).emitOn(executor);
}

public Uni<ItemDetailsResponse> callGetItemDetail(){
        Supplier<ItemDetailsResponse> supplier = () -> itemService.getItemDetail("dummy_item_id");
        return Uni.createFrom().item(supplier).emitOn(executor) ;
    }

executor is :

  ExecutorService executor = Executors.newFixedThreadPool(2);

but they still works in same thread. Do you have any idea why it happens?

Answer 1

Since you are composing different Uni s using Uni.combine().all().unis().asTuple() , the combined Uni will emit its result (combination) after the last element has emitted its item.

The last (upstream) Uni will have its item emitted (as is the case for other Uni s as well) on whatever Thread that you have declaratively set it to emit on. Hence the combination Uni will follow execution on the same calling Thread .

As a result, if you are accessing the combined group values, you will be accessing these on the same execution carrier Thread .