Using ChainState as Chain Backend

Recall that UtreexoNode is the high-level component of Floresta that will interact with the P2P network. It is made of its Context and a NodeCommon that holds a Chain backend (for validation and state tracking). This and the following chapters will focus solely on the Floresta chain backend.

In this chapter we will learn about ChainState, a type that implements UpdatableChainstate + BlockchainInterface, so we can use it as Chain backend.

ChainState is the default blockchain backend provided by Floresta, with all its logic encapsulated within the floresta-chain library.

The following associations clarify the module structure:

• UtreexoNode declaration and logic resides in floresta-wire
• ChainState declaration and logic resides in floresta-chain

ChainState Structure

The job of ChainState is to validate blocks, update the state and store it.

For a node to keep track of the chain state effectively, it is important to ensure the state is persisted to some sort of storage system. This way the node progress is saved, and we can recover it after the device is turned off.

That's why ChainState uses a generic PersistedState type, bounded by the ChainStore trait, which defines how we interact with our persistent state database.

Figure 2: Diagram of the ChainState type.

Filename: pruned_utreexo/chain_state.rs

// Path: floresta-chain/src/pruned_utreexo/chain_state.rs

pub struct ChainState<PersistedState: ChainStore> {
    inner: RwLock<ChainStateInner<PersistedState>>,
}

// Path: floresta-chain/src/pruned_utreexo/chain_state.rs

impl<PersistedState: ChainStore> BlockchainInterface for ChainState<PersistedState> {
    // Implementation of BlockchainInterface for ChainState

// Path: floresta-chain/src/pruned_utreexo/chain_state.rs

impl<PersistedState: ChainStore> UpdatableChainstate for ChainState<PersistedState> {
    // Implementation of UpdatableChainstate for ChainState

As Floresta is currently only pruned, the expected database primarily consists of the block header chain and the utreexo accumulator; blocks themselves are not stored.

The default implementation of ChainStore is KvChainStore, which uses a key-value store. This means that developers may:

• Implement custom UpdatableChainstate + BlockchainInterface types for use as Chain backends.
• Use the provided ChainState backend:
  • With their own ChainStore implementation.
  • Or the provided KvChainStore.

Next, let’s build the ChainState struct step by step!