Module 28: Axum State Middleware

Practice Tasks

Complete these tasks to reinforce what you learned in this module.

Task 1: Shared state counter

Create an AppState with a counter (e.g. AtomicU32 inside an Arc). Attach it to the router with .with_state(state). Add a GET / handler that uses State<AppState>, increments the counter, and returns the current count as a string. Run the server on port 3000.

Expected Output:

Each `curl http://127.0.0.1:3000/` returns `count: 0`, `count: 1`, `count: 2`, etc.

Hint: The state type must be Clone; wrap a counter in Arc so all clones share it. Attach state with .with_state(...). In the handler, use the State extractor and increment the counter (e.g. with an atomic).

Starter Code:

task.rs

// Task 1: Shared state counter. See tasks/TASKS.md.

fn main() {
    todo!("AppState with counter, with_state, handler");
}

Task 2: Add TraceLayer

Add tower_http::trace::TraceLayer::new_for_http() to the router with .layer(...). Use the same or a minimal route. Run and make a request; you should see trace output in the console.

Expected Output:

Console shows request trace (method, path, status) when you curl the server.

Hint: Add a layer to the router with .layer(...). The theory mentions TraceLayer for request logging; add it so the server logs requests.

Starter Code:

task.rs

// Task 2: Add TraceLayer. See tasks/TASKS.md.

fn main() {
    todo!("Router with TraceLayer::new_for_http()");
}