Stateful triggers

[JPaja]

Would you like to work on this feature?

yes

What problem are you trying to solve?

Currently internal trigger functions (watches, owns, etc..) cannot reconcile parent reference when resource is removed or reference inside resource is modified/removed.

Because of this managing Custom Resources like Service that rely on selectors is much harder.

Describe the solution you'd like

create *_stateful' variant of internal trigger functions (trigger_with,trigger_others, trigger_others_shared, trigger_owners, trigger_owners_shared`)

where new implementation trigger_with (trigger_with_stateful) would create new Mapper stream that would contain state.
State would have some kind of HashMap that would keep previously produced ObjectReferences from mapper function. If cached ObjectReference is not included in new mapper result, it would still produce ReconcileRequest and it would be removed from cache.

And potentially new ReconcileReason could be added ObjectRelationRemoved { obj_ref: Box<ObjectRef<DynamicObject>> }

Describe alternatives you've considered

Alternative of creating _stateful variant of functions would be to add new parameter to watcher::Config that would enable relation caching.

Documentation, Adoption, Migration Strategy

No response

Target crate for feature

kube-runtime