Rust区块链共识引擎库sc-consensus-epochs的使用，实现Substrate框架下的可配置分时纪元机制

概述

sc-consensus-epochs是用于基于纪元的共识引擎的通用工具库。它提供了在Substrate框架中实现可配置分时纪元机制的基础设施。

安装

在项目目录中运行以下Cargo命令：

cargo add sc-consensus-epochs

或者在Cargo.toml中添加：

sc-consensus-epochs = "0.50.0"

示例代码

以下是一个使用sc-consensus-epochs实现可配置分时纪元机制的完整示例：

use sc_consensus_epochs::{Epoch, epoch_changes::EpochChanges, SharedEpochChanges};
use sp_consensus::Error as ConsensusError;
use sp_runtime::traits::{Block as BlockT, NumberFor};
use std::sync::Arc;

// 定义纪元描述符结构
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct EpochDescriptor<B: BlockT> {
    pub epoch_start: NumberFor<B>,
    pub epoch_end: NumberFor<B>,
    pub epoch_duration: NumberFor<B>,
}

// 实现纪元变化跟踪器
pub struct EpochTracker<B: BlockT, E> {
    epoch_changes: SharedEpochChanges<B, E>,
}

impl<B: BlockT, E> EpochTracker<B, E> {
    // 创建新的纪元跟踪器
    pub fn new() -> Self {
        Self {
            epoch_changes: SharedEpochChanges::new(),
        }
    }

    // 添加新纪元
    pub fn add_epoch(
        &self,
        epoch_start: NumberFor<B>,
        epoch_end: NumberFor<B>,
        epoch_duration: NumberFor<B>,
        epoch_data: E,
    ) -> Result<(), ConsensusError> {
        let descriptor = EpochDescriptor {
            epoch_start,
            epoch_end,
            epoch_duration,
        };

        let mut epoch_changes = self.epoch_changes.shared_data();
        epoch_changes.import(
            descriptor,
            epoch_start,
            epoch_data,
        )?;

        Ok(())
    }

    // 获取当前纪元
    pub fn current_epoch(&self, block_number: NumberFor<B>) -> Option<Epoch<E>> {
        let epoch_changes = self.epoch_changes.shared_data();
        epoch_changes.epoch_data(&block_number, |slot| slot)
    }
}

// 使用示例
fn main() {
    type BlockNumber = u64;
    type TestEpochData = String;

    let epoch_tracker = EpochTracker::<BlockNumber, TestEpochData>::new();

    // 添加纪元配置
    epoch_tracker.add_epoch(
        0,      // 纪元开始区块
        100,    // 纪元结束区块
        10,     // 纪元持续时间(区块数量)
        "First Epoch".to_string(), // 纪元数据
    ).unwrap();

    // 查询纪元信息
    if let Some(epoch) = epoch_tracker.current_epoch(50) {
        println!("Current epoch data: {}", epoch.data);
        println!("Epoch start: {}", epoch.start_slot);
        println!("Epoch end: {}", epoch.end_slot);
    }
}

完整示例扩展

下面是一个更完整的示例，展示了如何在Substrate运行时中使用sc-consensus-epochs：

use sc_consensus_epochs::{
    Epoch, epoch_changes::{EpochChanges, EpochChangesFor}, 
    SharedEpochChanges, EpochHeader
};
use sp_consensus::{Error as ConsensusError, SelectChain};
use sp_runtime::{
    traits::{Block as BlockT, NumberFor, Zero},
    generic::BlockId,
};
use std::{sync::Arc, marker::PhantomData};

// 自定义纪元数据
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct CustomEpochData {
    pub validator_set: Vec<String>,
    pub randomness: [u8; 32],
}

// 纪元管理器
pub struct EpochManager<B: BlockT, C> {
    epoch_changes: SharedEpochChanges<B, CustomEpochData>,
    client: Arc<C>,
    _phantom: PhantomData<B>,
}

impl<B: BlockT, C> EpochManager<B, C> 
where
    C: SelectChain<B>,
{
    pub fn new(client: Arc<C>) -> Self {
        Self {
            epoch_changes: SharedEpochChanges::new(),
            client,
            _phantom: PhantomData,
        }
    }

    // 初始化创世纪元
    pub fn initialize_genesis_epoch(
        &self,
        epoch_data: CustomEpochData,
    ) -> Result<(), ConsensusError> {
        let mut epoch_changes = self.epoch_changes.shared_data();
        epoch_changes.import(
            EpochHeader {
                start_slot: Zero::zero(),
                end_slot: Zero::zero(),
            },
            Zero::zero(),
            epoch_data,
        )?;
        Ok(())
    }

    // 获取或创建新纪元
    pub fn get_or_create_epoch(
        &self,
        parent_hash: B::Hash,
        slot_number: NumberFor<B>,
    ) -> Result<Epoch<CustomEpochData>, ConsensusError> {
        let epoch_changes = self.epoch_changes.shared_data();
        let chain_head = self.client.best_chain()?;
        
        epoch_changes.epoch_data_for_child_of(
            &parent_hash,
            &chain_head,
            slot_number,
            |slot| slot,
        )
    }

    // 添加新纪元配置
    pub fn add_epoch_configuration(
        &self,
        start_slot: NumberFor<B>,
        end_slot: NumberFor<B>,
        epoch_data: CustomEpochData,
    ) -> Result<(), ConsensusError> {
        let mut epoch_changes = self.epoch_changes.shared_data();
        epoch_changes.import(
            EpochHeader {
                start_slot,
                end_slot,
            },
            start_slot,
            epoch_data,
        )?;
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use sc_consensus::LongestChain;
    use sp_core::H256;
    use substrate_test_runtime_client::{
        runtime::{Block, Header},
        TestClientBuilder, TestClientBuilderExt,
    };

    #[test]
    fn test_epoch_management() {
        let builder = TestClientBuilder::new();
        let client = Arc::new(builder.build());
        let select_chain = LongestChain::new(client.backend());
        
        let epoch_manager = EpochManager::<Block, _>::new(Arc::new(select_chain));
        
        let genesis_data = CustomEpochData {
            validator_set: vec!["Alice".into(), "Bob".into()],
            randomness: [0u8; 32],
        };
        
        epoch_manager.initialize_genesis_epoch(genesis_data.clone()).unwrap();
        
        // 添加新纪元配置
        let new_epoch_data = CustomEpochData {
            validator_set: vec!["Charlie".into(), "Dave".into()],
            randomness: [1u8; 32],
        };
        
        epoch_manager.add_epoch_configuration(1, 100, new_epoch_data.clone()).unwrap();
        
        // 获取纪元信息
        let header = Header {
            parent_hash: H256::zero(),
            number: 1,
            state_root: H256::zero(),
            extrinsics_root: H256::zero(),
            digest: Default::default(),
        };
        
        let epoch = epoch_manager.get_or_create_epoch(header.hash(), 1).unwrap();
        assert_eq!(epoch.data.validator_set, new_epoch_data.validator_set);
    }
}

关键功能

1. 纪元管理：创建和管理区块链的不同纪元阶段
2. 纪元过渡：平滑处理纪元之间的过渡
3. 可配置性：允许自定义纪元长度和参数
4. 线程安全：通过SharedEpochChanges提供线程安全的纪元访问

许可证

该库采用GPL-3.0-or-later许可证，并带有Classpath-exception-2.0附加条款。