Mutiny Multi and Quarkus Caching

[Manuel Wallrapp]

Hi everyone

We used mutiny to develop our backend services. We cached some data with the Quarkus  @CacheResult annotation. While this works ok for Uni's, since Caffein also uses Uni's under the hood. 

How is caching done for Multi's? 

It would be great to have a more clear explanation how to cache Uni's AND Multi's in the Quarkus caching guide.

If in the @CacheResult annotated method I subscribe to a multi and collect it and then return a Uni<List<MyType>> it tells me, I am blocking the thread.  

@CacheResult(cacheName = BITBUCKET_REPO_BRANCHES)
public Uni<List<GitBranchDto>> getBranchesForRepo(String projectKey, String repositorySlug) {
return Uni.createFrom().item(
bitbucketClient.getBranchesForRepo(projectKey, repositorySlug, PageRequest.fetchAll())
.subscribe()
.asStream()
.collect(Collectors.toList()))
;
}

In general I miss also a guide for caching in the Mutiny Guide. 

Thanks for your help

Manu

[clement escoffier]

Hello,

I don't believe we support caching Multi. Julien Ponge is working on a Multi operator that may let you do this (replay, which will replay the last items). 

In your code, you are blocking because `asStream` returns a blocking stream. So, it blocks until you read all the items (and accumulate them in a list). It would have been similar to:

```
List<GitBranchDto> list = .... # get the list using a blocking API
return Uni.createFrom().item(list);
```

You need to do something like:

```

@CacheResult(cacheName = BITBUCKET_REPO_BRANCHES)
public Uni<List<GitBranchDto>> getBranchesForRepo(String projectKey, String repositorySlug) {

 return bitbucketClient.getBranchesForRepo(projectKey, repositorySlug, PageRequest.fetchAll()).collect().asList();
}
```

The difference is that you do not block. You return a Uni that will emit its item when you read all the items from the Multi.

Clement

[Julien Ponge]

Replaying of Multi is indeed on the radar (and it's a not that simple!).

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