Dmitry Markin
1cd6acdff3
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.
Integration of the GRANDPA finality gadget into Substrate.
This crate is unstable and the API and usage may change.
This crate provides a long-running future that produces finality notifications.
Usage
First, create a block-import wrapper with the block_import function. The
GRANDPA worker needs to be linked together with this block import object, so
a LinkHalf is returned as well. All blocks imported (from network or
consensus or otherwise) must pass through this wrapper, otherwise consensus
is likely to break in unexpected ways.
Next, use the LinkHalf and a local configuration to run_grandpa_voter.
This requires a Network implementation. The returned future should be
driven to completion and will finalize blocks in the background.
Changing authority sets
The rough idea behind changing authority sets in GRANDPA is that at some point, we obtain agreement for some maximum block height that the current set can finalize, and once a block with that height is finalized the next set will pick up finalization from there.
Technically speaking, this would be implemented as a voting rule which says, "if there is a signal for a change in N blocks in block B, only vote on chains with length NUM(B) + N if they contain B". This conditional-inclusion logic is complex to compute because it requires looking arbitrarily far back in the chain.
Instead, we keep track of a list of all signals we've seen so far (across all forks), sorted ascending by the block number they would be applied at. We never vote on chains with number higher than the earliest handoff block number (this is num(signal) + N). When finalizing a block, we either apply or prune any signaled changes based on whether the signaling block is included in the newly-finalized chain.
License: GPL-3.0-or-later WITH Classpath-exception-2.0