Chapter 20 — Health checks

3 tests, no DB — rustango::health::HealthRouter. Run with cargo test --test cookbook_chapter20_health.

/health is liveness (always 200 {"status":"ok"}, probes nothing — point your load balancer here). /ready is readiness: it pings the DB (SELECT 1) and runs every registered check, returning 200 when all pass and 503 (with the failing check named) when any fails — the shape a rollout / deploy gate wants.

use rustango::health::HealthRouter;

let health = HealthRouter::new(pool)
    .tcp_probe("redis", "127.0.0.1:6379")
    .check("payments", || async { ping_gateway().await })
    .into_router();
app.merge(health);

• §20.148 — /health liveness → 200 {"status":"ok"}. → health_liveness_is_ok
• §20.149 — /ready with all checks passing → 200, each check reports status + latency_ms. → ready_ok_when_all_checks_pass
• §20.150 — a failing check flips /ready to 503 and names the unhealthy downstream. → ready_503_when_a_check_fails

(.tcp_probe / .cache_probe / .http_probe add ready-probes for downstreams; .skip_db_probe() drops the built-in SELECT 1.)