Extract `WarpSync` (and `StateSync` as part of warp sync) from
`ChainSync` as independent syncing strategy called by `SyncingEngine`.
Introduce `SyncingStrategy` enum as a proxy between `SyncingEngine` and
specific syncing strategies.
## Limitations
Gap sync is kept in `ChainSync` for now because it shares the same set
of peers as block syncing implementation in `ChainSync`. Extraction of a
common context responsible for peer management in syncing strategies
able to run in parallel is planned for a follow-up PR.
## Further improvements
A possibility of conversion of `SyncingStartegy` into a trait should be
evaluated. The main stopper for this is that different strategies need
to communicate different actions to `SyncingEngine` and respond to
different events / provide different APIs (e.g., requesting
justifications is only possible via `ChainSync` and not through
`WarpSync`; `SendWarpProofRequest` action is only relevant to
`WarpSync`, etc.)
---------
Co-authored-by: Aaro Altonen <48052676+altonen@users.noreply.github.com>
Previously, it was only possible to retry the same request on a
different protocol name that had the exact same binary payloads.
Introduce a way of trying a different request on a different protocol if
the first one fails with Unsupported protocol.
This helps with adding new req-response versions in polkadot while
preserving compatibility with unupgraded nodes.
The way req-response protocols were bumped previously was that they were
bundled with some other notifications protocol upgrade, like for async
backing (but that is more complicated, especially if the feature does
not require any changes to a notifications protocol). Will be needed for
implementing https://github.com/polkadot-fellows/RFCs/pull/47
TODO:
- [x] add tests
- [x] add guidance docs in polkadot about req-response protocol
versioning
This PR moves syncing-related code from `sc-network-common` to
`sc-network-sync`.
Unfortunately, some parts are tightly integrated with networking, so
they were left in `sc-network-common` for now:
1. `SyncMode` in `common/src/sync.rs` (used in `NetworkConfiguration`).
2. `BlockAnnouncesHandshake`, `BlockRequest`, `BlockResponse`, etc. in
`common/src/sync/message.rs` (used in `src/protocol.rs` and
`src/protocol/message.rs`).
More substantial refactoring is needed to decouple syncing and
networking completely, including getting rid of the hardcoded sync
protocol.
## Release notes
Move syncing-related code from `sc-network-common` to `sc-network-sync`.
Delete `ChainSync` trait as it's never used (the only implementation is
accessed directly from `SyncingEngine` and exposes a lot of public
methods that are not part of the trait). Some new trait(s) for syncing
will likely be introduced as part of Sync 2.0 refactoring to represent
syncing strategies.
Dmitry Markin