- 2020-06-30: Initial draft
- 2020-07-02: approved with corrections
The initial approach to use callbacks in order to capture async responses
from requests issued by the Handle to its Supervisor introduces a couple of
drawbacks, i.e. try semantics, scope and borrow complexities. As the
general pattern seems to be that a bounded channel is constructed to transport
the response it could be reworked to be the actual value send with the event to
the Supervisor. Which in turn send back the response on the typed channel to the
Handle. As an added side-effect this could remove the need for the Callback
abstraction all together and fully embraces CSP style concurrency.
Furthermore we have async versions of most Handle methods, but no real
use-case driving it. At this point we can't anticipate the limitations of the
current design with regards to concurrent access.
Remove the callback abstraction in favour of passing channels in the events
exchanged directly as the pattern is present already in the current concrete
implementation of the supervisor::Handle anyway.
Remove async versions of the public methods until a use-case drives their implementation. We will leave concurrency to be informed by emerging use-cases and field reports. With the first real integration likely happen in the RPC server and ibc relayer.
Approved
- Smaller public surface of the Handle abstraction
- Removal of Callback type
- Easier to reason code
- No explicit async version of Supervisor methods