Improve shared streams interfaces

[mateiidavid]

Would you like to work on this feature?

yes

What problem are you trying to solve?

We added experimental support for shared stream interfaces in PR #1449. Although the change is code complete, it has some rough edges.

Improvements

• Introduce a new type to do writes against the store.

  • All writes on a store are handled through Writer<K>. There are two different types of writers: those that are backed by a channel (and can distribute events to listeners) and those that are not. We should differentiate between these two different contracts by introducing an appropriate type for a "shared" writer. This will allow us to avoid awkward public interface, like the subscribe() method

• Return a concrete type that implements Stream from reflector().

  • It would be good to try and change the type returned by a reflector(). Because a writer can now broadcast events to listeners, it has to call into an async function when a watcher stream is threaded through it. To keep it simple, we are using the stream! macro, but it tends to obfuscate the implementation. It would be nicer to deal with a concrete type here (which in turn might make subscribing easier)

• Shared streams Controller interfaces for relations (watches_shared_stream and owns_shared_stream)

  • We should extend for_shared_stream in such a way that Controllers may accept shared streams for owned objects.

Parts of this have already been mentioned as future work in #1080.

Describe the solution you'd like

N/A

Describe alternatives you've considered

N/A

Documentation, Adoption, Migration Strategy

No response

Target crate for feature

kube-runtime