How to reactive with quarkus-mutiny

[Daniel Borella]

Hello Quarkus community,

I'm struggling with my first attempts to create a reactive service (preferably with Mutiny).

The use case is the following:

I get a list of items from an async api (Promise SearchResult),

then I complete (transform) each item with other information (new type),

before I send the item to storage.

This pretty much sound like a nice stream. So, my first idea was wrapping things:

public Multi<Item> getResult(){

ItemResult result = async.call().get() // get of the Promise

return Multi.createFrom().iterable(result.getItems());

}

And

public Uni<CustomType> buildCutomType(Item item){

//Do stuff to build new obj

return Uni.createFrom().item(obj);

}

The problem I have is to find the correct sequence of functions like:

adapter.getResult() //return Multi<Item>

                .onItem()

                .transform(item -> buildCutomType(item)) //as this returns Uni<CustomType> do I need to "transformToUni"?

                .onItem()

                .call(obj -> repo.store(obj)); //necessary to wait at the end for completion?

Maybe, the approach to wrap things like above is already wrong, and it's better to return a Uni<ItemResult> at the beginning, but then again I need to stream the single items out of it?? Hmmm :-/

I checked the "reactive" topics in the guides and the Mutiny docs, but there is a lack of complex examples.

A little guidance on that topic would be very much appreciated 

Regards,

Daniel

[Julien Ponge]

Hi Daniel,

It's a bit hard to say with just a few snippets, but note that:

• transform models synchronous transformations (e.g., extracting a JSON entry from a payload)
• transformToUni models asynchronous transformations (hence the mapping function returns a Uni), think of indeed making a call to another service for each item
• if buildCustomType does not do I/O it might just be a transform
• looks like repo.store(obj) is a candidate for another transformToUni

Hope it helps.

---

From: quark...@googlegroups.com <quark...@googlegroups.com> on behalf of Daniel Borella <borella...@gmail.com>
Sent: Wednesday, October 13, 2021 8:28 AM
To: Quarkus Development mailing list <quark...@googlegroups.com>
Subject: [quarkus-dev] How to reactive with quarkus-mutiny

 

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