识别当 Tokio 工作员过于繁忙而无法处理更多工作时的情况。

监控 Tokio 工作员的繁忙比例

TooBusy 允许您跟踪 Tokio 工作员的繁忙比例，并在它们过于繁忙时相应地做出反应。

在下面的示例中，创建并使用了一个 TooBusy 来评估 Tokio 工作员的繁忙比例，并在繁忙比例超过低水位阈值时逐步拒绝请求

use axum::{
    extract::{Request, State},
    http::StatusCode,
    middleware::{self, Next},
    response::{IntoResponse, Response},
    routing::get,
    Router,
};
use tokio::time::Duration;
use tokio_too_busy::*;

#[derive(Clone)]
struct AppState {
    too_busy: TooBusy,
}

async fn root() -> &'static str {
    "Hello, World!"
}

async fn my_middleware(State(state): State<AppState>, request: Request, next: Next) -> Response {
   if state.too_busy.eval() {
       return (StatusCode::SERVICE_UNAVAILABLE, "Server is too busy").into_response();
   }
   next.run(request).await
}

#[tokio::main(flavor = "multi_thread", worker_threads = 1)]
async fn main() {
   let too_busy = TooBusy::builder()
       .interval(Duration::from_secs(1))
       .ewma_alpha(0.1)
       .high_watermark(95)
       .low_watermark(90)
       .build();

   let state = AppState { too_busy };

   let app = Router::new()
      .route("/", get(root))
      .route_layer(middleware::from_fn_with_state(state.clone(), my_middleware))
      .with_state(state);

  let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
  axum::serve(listener, app).await.unwrap();
}