Rust跨链交互库cumulus-relay-chain-interface的使用，实现Polkadot平行链与中继链高效通信

安装

在项目目录中运行以下Cargo命令：

cargo add cumulus-relay-chain-interface

或者在Cargo.toml中添加以下行：

cumulus-relay-chain-interface = "0.25.0"

示例代码

以下是使用cumulus-relay-chain-interface实现Polkadot平行链与中继链通信的完整示例：

use cumulus_relay_chain_interface::{RelayChainInterface, RelayChainResult};
use polkadot_service::client::Client;
use sc_service::Configuration;
use sp_runtime::traits::Block as BlockT;

// 创建中继链接口
async fn create_relay_chain_interface() -> RelayChainResult<impl RelayChainInterface> {
    // 配置中继链连接参数
    let config = Configuration {
        chain_spec: Box::new(polkadot_service::chain_spec::polkadot_config()),
        // 其他配置参数...
        ..Default::default()
    };
    
    // 创建客户端
    let client = Client::new(config).await?;
    
    // 创建中继链接口
    RelayChainInterface::new(client)
}

// 获取中继链最新区块高度
async fn get_relay_chain_block_number(
    relay_chain_interface: &impl RelayChainInterface,
) -> RelayChainResult<u32> {
    relay_chain_interface.best_block_number().await
}

// 提交平行链区块到中继链
async fn submit_parachain_block_to_relay(
    relay_chain_interface: &impl RelayChainInterface,
    parachain_block: Vec<u8>,
) -> RelayChainResult<()> {
    relay_chain_interface
        .submit_block_to_relay_chain(parachain_block)
        .await
}

// 主函数示例
#[tokio::main]
async fn main() -> RelayChainResult<()> {
    // 创建中继链接口
    let relay_chain_interface = create_relay_chain_interface().await?;
    
    // 获取中继链最新区块高度
    let block_number = get_relay_chain_block_number(&relay_chain_interface).await?;
    println!("Relay chain best block number: {}", block_number);
    
    // 模拟平行链区块数据
    let parachain_block = vec![0x1, 0x2, 0x3];
    
    // 提交平行链区块到中继链
    submit_parachain_block_to_relay(&relay_chain_interface, parachain_block).await?;
    
    Ok(())
}

完整示例代码

以下是一个更完整的示例，包含了更多实用功能：

use cumulus_relay_chain_interface::{RelayChainInterface, RelayChainResult};
use polkadot_service::client::Client;
use sc_service::Configuration;
use sp_runtime::{traits::Block as BlockT, generic::BlockId};

// 创建中继链接口
async fn create_relay_chain_interface() -> RelayChainResult<impl RelayChainInterface> {
    // 配置中继链连接参数
    let config = Configuration {
        chain_spec: Box::new(polkadot_service::chain_spec::polkadot_config()),
        transport: polkadot_service::build_network_transport(),
        ..Default::default()
    };
    
    // 创建客户端
    let client = Client::new(config).await?;
    
    // 创建中继链接口
    RelayChainInterface::new(client)
}

// 获取中继链最新区块头
async fn get_relay_chain_header(
    relay_chain_interface: &impl RelayChainInterface,
) -> RelayChainResult<Option<sp_runtime::generic::Header<u32, sp_runtime::traits::BlakeTwo256>>> {
    let best_hash = relay_chain_interface.best_block_hash().await?;
    relay_chain_interface.header(BlockId::Hash(best_hash)).await
}

// 监听中继链新块事件
async fn watch_relay_chain_blocks(
    relay_chain_interface: impl RelayChainInterface,
) -> RelayChainResult<()> {
    let mut import_notification_stream = relay_chain_interface.import_notification_stream().await?;
    
    while let Some(notification) = import_notification_stream.next().await {
        println!(
            "New relay chain block: #{} ({})",
            notification.header.number,
            notification.hash
        );
    }
    
    Ok(())
}

// 主函数示例
#[tokio::main]
async fn main() -> RelayChainResult<()> {
    // 创建中继链接口
    let relay_chain_interface = create_relay_chain_interface().await?;
    
    // 获取中继链最新区块信息
    let block_number = get_relay_chain_block_number(&relay_chain_interface).await?;
    println!("Relay chain best block number: {}", block_number);
    
    // 获取最新区块头
    if let Some(header) = get_relay_chain_header(&relay_chain_interface).await? {
        println!("Latest block header: {:?}", header);
    }
    
    // 启动监听线程
    let interface_clone = relay_chain_interface.clone();
    tokio::spawn(async move {
        if let Err(e) = watch_relay_chain_blocks(interface_clone).await {
            eprintln!("Error watching relay chain blocks: {}", e);
        }
    });
    
    // 模拟平行链区块数据
    let parachain_block = vec![0x1, 0x2, 0x3];
    
    // 提交平行链区块到中继链
    submit_parachain_block_to_relay(&relay_chain_interface, parachain_block).await?;
    
    Ok(())
}

主要功能

1. 创建中继链连接：通过RelayChainInterface::new()建立与中继链的连接
2. 获取中继链信息：如最新区块高度、区块头等
3. 监听中继链事件：实时获取新块通知
4. 提交平行链数据：将平行链区块提交到中继链

注意事项

• 使用前需要确保正确配置中继链连接参数
• 所有操作都是异步的，需要使用async/await语法
• 错误处理通过RelayChainResult类型进行
• 克隆接口实例可以在多个任务中安全使用