rust.tokio.missing_graceful_shutdown

Stability High

Detects Tokio applications without graceful shutdown handling.

Why It Matters

Without graceful shutdown:

Data loss — In-progress requests terminated mid-operation
Broken connections — Clients see connection reset errors
Database corruption — Transactions interrupted
Deploy failures — Kubernetes kills pods that don’t stop cleanly

Graceful shutdown lets existing work complete before the process exits.

Example

// ❌ Before
#[tokio::main]
async fn main() {
    let app = Router::new().route("/", get(handler));

    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

SIGTERM kills the process immediately.

// ✅ After
use tokio::signal;

#[tokio::main]
async fn main() {
    let app = Router::new().route("/", get(handler));

    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .with_graceful_shutdown(shutdown_signal())
        .await
        .unwrap();
}

async fn shutdown_signal() {
    let ctrl_c = async {
        signal::ctrl_c()
            .await
            .expect("failed to install Ctrl+C handler");
    };

    #[cfg(unix)]
    let terminate = async {
        signal::unix::signal(signal::unix::SignalKind::terminate())
            .expect("failed to install signal handler")
            .recv()
            .await;
    };

    #[cfg(not(unix))]
    let terminate = std::future::pending::<()>();

    tokio::select! {
        _ = ctrl_c => {},
        _ = terminate => {},
    }
}

What Unfault Detects

Tokio main without signal handling
Server without with_graceful_shutdown
Missing SIGTERM handler

Auto-Fix

Unfault adds graceful shutdown signal handling.

Best Practices

// Set a shutdown timeout
let server = axum::Server::bind(&addr)
    .serve(app.into_make_service())
    .with_graceful_shutdown(shutdown_signal());

// Force shutdown after timeout
tokio::select! {
    _ = server => {},
    _ = tokio::time::sleep(Duration::from_secs(30)) => {
        tracing::warn!("graceful shutdown timed out, forcing exit");
    }
}

// Cleanup resources
cleanup_connections().await;
flush_metrics().await;