Alt Block/ Chain Handling

[Boog900]

What

Adding alt block handling to Cuprate's components, the consensus and DB code needs to be able to handle reorgs.

The block downloader can already handle downloading an alt chain.

How

Consensus changes

The consensus changes are being completed in this PR: #214

Database changes

#214 makes some changes to the BCRequest/response enums these new requests will need to be handled in the DB.

To do this some new tables will need to be added:

AltChainsInfo

Key: ChainID
Value: AltChainInfo

struct AltChainInfo {
    parent_chain: Chain,
    common_ancestor_height: u64
}

AltBlockHeights

Key: Block Hash ([u8; 32]).
Value: AltBlockHeight

struct AltBlockHeight {
     /// The ID of the alt chain the alt block is on.
    chain_id: ChainID,
    height: u64
}

AltBlocksInfo

Key: AltBlockHeight
Value: CompactAltBlockInfo

struct CompactAltBlockInfo {
    /// The block's hash.
    ///
    /// [`Block::hash`].
    pub block_hash: [u8; 32],
    /// The block's proof-of-work hash.
    pub pow_hash: [u8; 32],
    /// The block's height.
    pub height: u64,
    /// The adjusted block size, in bytes.
    pub weight: usize,
    /// The long term block weight, which is the weight factored in with previous block weights.
    pub long_term_weight: usize,
    /// The cumulative difficulty of all blocks up until and including this block.
    pub cumulative_difficulty: u128,
}

AltBlockBlobs

Key: AltBlockHeight
Value: Vec<u8>

AltTransactionBlobs

Key: Tx hash ([u8; 32])
Value: Vec<u8>

AltTransactionsInfo

Key: Tx hash ([u8; 32])
Value: AltTransactionInfo

struct AltTransactionInfo {
    /// The transaction's weight.
    ///
    /// [`Transaction::weight`].
    pub tx_weight: usize,
    /// The transaction's total fees.
    pub fee: u64,
    /// The transaction's hash.
    ///
    /// [`Transaction::hash`].
    pub tx_hash: [u8; 32],
}

DB request changes

And some new request variants need to be added:

// https://github.com/Cuprate/cuprate/blob/dced4ed7ecd6f5a93b0102f3bde6bf13ad5aff4d/types/src/blockchain.rs#L110
pub enum BCWriteRequest {
    ....

    /// Pop some blocks from the top of the main chain, adding the popped blocks to the alt block tables 
    PopBlocks(usize),
    /// Add an alt block to the alt block tables.
    AddAltBlock(AltBlockInformation),
    /// Clear all alt block tables.
    FlushAltBlocks,
}

// https://github.com/Cuprate/cuprate/blob/dced4ed7ecd6f5a93b0102f3bde6bf13ad5aff4d/types/src/blockchain.rs#L24
pub enum BCReadRequest {
    ....

    /// Returns all blocks in an alt chain up to the point the chain meets the main chain.
    /// The input is the top block hash in the alt chain 
    AltChain([u8; 32])
}

// https://github.com/Cuprate/cuprate/blob/dced4ed7ecd6f5a93b0102f3bde6bf13ad5aff4d/types/src/blockchain.rs#L125
pub enum BCResponse {
    ....
    /// A list of alt blocks in chronological order.
    AltChain(Vec<AltBlockInformation>)
    

These todos also need to be completed:

cuprate/storage/blockchain/src/service/read.rs

Line 210 in dced4ed

R::FindBlock(_) => todo!("Add alt blocks to DB"),

cuprate/storage/blockchain/src/service/read.rs

Line 326 in dced4ed

Chain::Alt(_) => todo!("Add alt blocks to DB"),

cuprate/storage/blockchain/src/service/read.rs

Line 382 in dced4ed

Chain::Alt(_) => todo!("Add alt blocks to DB"),