05 | Command Line & Config File

05 | Command Line & Config File

This is a hands-on tutorial, so please switch to the corresponding code branch before reading.

Repo: https://github.com/jacob-chia/tinychain.git

Branch：git fetch && git switch 05-cmd-config

Important crates used in this lesson:

clap: Command Line Argument Parser for Rust

toml: A serde-compatible TOML-parsing library

In this lesson, we will add two commands:

new-account: create an account and return the address. The account storage path can be specified by parameters.
run: run the tinychain node service. The running parameters are passed in through the configuration file.

1 Defining Command Line Arguments

Define the Opts and SubCommand according to the requirements of clap. Let's look at the code directly.

// src/main.rs

/// The command of tinychain
#[derive(Debug, Parser)]
struct Opts {
    #[command(subcommand)]
    subcmd: SubCommand,
}

#[derive(Debug, Subcommand)]
enum SubCommand {
    /// Create a new account for signing transactions
    NewAccount {
        /// the keystore directory, default is `./db/keystore/`
        #[arg(short, long, default_value_t = String::from("./db/keystore/"))]
        keystore_dir: String,
    },
    /// Run the node
    Run {
        /// the config file path, default is `config.toml`
        #[arg(short, long, default_value_t = String::from("config.toml"))]
        config: String,
    },
}

2 Parsing and Executing Commands

// src/main.rs

#[tokio::main]
async fn main() {
    pretty_env_logger::init();
    let opts = Opts::parse();
    match opts.subcmd {
        SubCommand::NewAccount { keystore_dir } => new_account(&keystore_dir),
        SubCommand::Run { config } => run(&config).await,
    }
}

fn new_account(keystore_dir: &str) {
    let wallet = Wallet::new(keystore_dir);
    let acc = wallet.new_account().unwrap();
    info!("📣 New account: {:?}", acc);
}

async fn run(config_file: &str) {
    let cfg = Config::load(config_file).unwrap();
    info!("📣 Config loaded: {:?}", cfg);

    // ...
}

When it comes to SubCommand::Run, we need to specify a configuration file, and here is a template: ./config-template.toml. Accordingly, a struct should be defined to deserialize the configuration file. The code is as follows:

// src/config.rs

#[derive(Clone, Debug, Default, Deserialize)]
pub struct Config {
    /// The path to the data directory.
    pub data_dir: String,
    /// The path to the genesis file.
    pub genesis_file: String,
    /// The address to listen on for HTTP Server.
    pub http_addr: String,
    /// The miner account to receive mining rewards.
    pub author: String,
    /// Wallet configuration.
    pub wallet: WalletConfig,
}

impl Config {
    /// Load the configuration from the given path.
    pub fn load(path: &str) -> Result<Self, Error> {
        let content =
            fs::read_to_string(path).map_err(|_| Error::ConfigNotExist(path.to_string()))?;

        let config: Config = toml::from_str(&content)?;
        Ok(config)
    }
}

3 Demo

Note: The log level in the code is info, so we need to add the RUST_LOG=info parameter when running.

Build: cargo build;
Check the commands: RUST_LOG=info ./target/debug/tinychain:
Create an account: RUST_LOG=info ./target/debug/tinychain new-account:
Run the service: RUST_LOG=info ./target/debug/tinychain run -c ./config-template.toml: