The sync controller (syncer) enforces a sync binding between two attribute sets. A binding can be of kind: Sync or Match.

Each attribute set is given by a URI, typically in the form of /namespace/name/[attributes]. If the URI points to a leaf attribute, then the attribute set contains only one element (the leaf); otherwise, all the attributes in the subtree will be considered as part of the binding.

The idea of a sync binding is simple:

• Attribute sets under Sync binding will be eventually synced to each other, e.g., an update to one will be reflected to the other. The two attribute sets need to share identical schemas.
• Attribute sets under Match binding will have the target eventually synced to the source.

A sync binding can be defined as:

apiVersion: ..
kind: Sync
spec:
    source: [AURI]
    target: [AURI]
    mode: [sync | match]

E.g.,

apiVersion: ..
kind: Sync
spec:
    source: /default/scene/spec/outputs/objects
    target: /default/null/spec/inputs/json
    mode: match

TBD: concurrent writes in a kind: Sync binding might with concurrent reconciliations TBD: sync with stronger than eventual guarantee.