xboot 0.1.19

static variables like module-level database connections can be initialized asynchronously before the program starts. / 在程序启动前通过异步函数初始化静态变量，如模块级数据库连接。
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# xboot

## English Readme

With the help of [linkme](https://github.com/dtolnay/linkme), call an asynchronous function to initialize static variables.

You can connect to the database before the program starts and set it as a module-level variable, refer to [xkv: redis global connector](https://crates.io/crates/xboot).

linkme will report an error when linking with `rust-lld` on Linux [Missing symbol on Linux](https://github.com/dtolnay/linkme/issues/107).

Please use [mold](https://github.com/rui314/mold) instead, and configure the environment variables as follows:

```
export RUSTFLAGS="$RUSTFLAGS -C linker=clang -C link-arg=-fuse-ld=/usr/bin/mold"
```

## 中文说明

借助 [linkme](https://github.com/dtolnay/linkme)，调用异步函数初始化静态变量。

可在程序启动之前连上数据库，并设置为一个模块级别的变量，参考  [xkv: redis 全局连接器](https://crates.io/crates/xboot) 。

linkme 在 Linux 上用 `rust-lld` 链接会报错 [Missing symbol on Linux](https://github.com/dtolnay/linkme/issues/107)

请改用 [mold](https://github.com/rui314/mold) ，配置环境变量如下:

```
export RUSTFLAGS="$RUSTFLAGS -C linker=clang -C link-arg=-fuse-ld=/usr/bin/mold"
```

## 演示代码

```rust
use aok::{Result, OK};
pub use async_wrap::Wrap;
use tracing::info;

pub mod inner {
  use aok::{Result, OK};
  use async_lazy::Lazy;
  use tokio::time::{sleep, Duration};
  use tracing::info;

  pub struct Client {}

  impl Client {
    pub async fn test(&self) {
      info!("client test success");
    }

    pub async fn connect(&self) -> Result<()> {
      info!("Sleeping for 3 seconds...");
      sleep(Duration::from_secs(3)).await;
      OK
    }
  }

  pub static CLIENT: Lazy<Client> = Lazy::const_new(|| {
    Box::pin(async {
      let client = Client {};
      loop {
        match client.connect().await {
          Ok(_) => {
            return client;
          }
          Err(err) => {
            tracing::error!("connect error: {}", err);
          }
        }
      }
    })
  });

  pub fn async_init() -> xboot::Task {
    tokio::task::spawn(async {
      use std::future::IntoFuture;
      CLIENT.into_future().await;
      OK
    })
  }

  #[linkme::distributed_slice(xboot::ASYNC)]
  static INIT: xboot::AsyncFn = async_init;
}

pub static CLIENT: Wrap<inner::Client> = Wrap::<inner::Client>(&inner::CLIENT);

#[tokio::main]
async fn main() -> Result<()> {
  xboot::init().await?;
  info!("inited");
  CLIENT.test().await;
  OK
}
```

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