feat(health): implement GET /health/deep readiness probe (#1)

src/routes/health.rs

@@ -3,3 +3,91 @@
 // GET /health/deep  - readiness probe (checks DB + Horizon connectivity)
 // Added by Chiamaka Eze (#159)
 pub const HEALTH_ROUTER_VERSION: &str = "1.0";
+
+use crate::AppState;
+use axum::{
+    extract::State,
+    http::StatusCode,
+    response::{IntoResponse, Response},
+    Json,
+};
+use serde_json::json;
+use std::sync::Arc;
+use std::time::Duration;
+
+/// GET /health/deep — readiness probe checking database and Horizon upstream connectivity.
+pub async fn health_deep(
+    State(state): State<Arc<AppState>>,
+) -> Response {
+    let mut is_healthy = true;
+    let mut database_status = "ok";
+    let mut horizon_status = "ok";
+
+    // 1. Check Database connectivity with timeout
+    let db_check = tokio::time::timeout(
+        Duration::from_secs(2),
+        sqlx::query("SELECT 1").execute(&state.pool),
+    )
+    .await;
+
+    match db_check {
+        Ok(Ok(_)) => {}
+        Ok(Err(e)) => {
+            tracing::warn!(error = %e, "health_deep: database check failed");
+            database_status = "error";
+            is_healthy = false;
+        }
+        Err(_) => {
+            tracing::warn!("health_deep: database check timed out");
+            database_status = "timeout";
+            is_healthy = false;
+        }
+    }
+
+    // 2. Check Horizon connectivity with timeout
+    let horizon_url = format!("{}/", state.config.horizon_url.trim_end_matches('/'));
+    let client = reqwest::Client::builder()
+        .timeout(Duration::from_secs(2))
+        .build();
+
+    match client {
+        Ok(c) => match c.get(&horizon_url).send().await {
+            Ok(resp) => {
+                if resp.status().is_success() {
+                    // Horizon root responded successfully
+                } else {
+                    tracing::warn!(status = %resp.status(), "health_deep: horizon check returned non-200");
+                    horizon_status = "error";
+                    is_healthy = false;
+                }
+            }
+            Err(e) => {
+                tracing::warn!(error = %e, "health_deep: horizon check failed");
+                horizon_status = "unreachable";
+                is_healthy = false;
+            }
+        },
+        Err(e) => {
+            tracing::warn!(error = %e, "health_deep: failed to build HTTP client for horizon check");
+            horizon_status = "error";
+            is_healthy = false;
+        }
+    }
+
+    let status_code = if is_healthy {
+        StatusCode::OK
+    } else {
+        StatusCode::SERVICE_UNAVAILABLE
+    };
+
+    let body = json!({
+        "success": is_healthy,
+        "data": {
+            "status": if is_healthy { "ok" } else { "degraded" },
+            "database": database_status,
+            "horizon": horizon_status,
+        }
+    });
+
+    (status_code, Json(body)).into_response()
+}

src/routes/mod.rs

@@ -1,6 +1,7 @@
 pub mod accounts;
 pub mod auth;
 pub mod escrows;
+pub mod health;
 pub mod keeper;
 pub mod payment_requests;
 pub mod payments;
@@ -20,6 +21,7 @@ pub fn build_router(state: Arc<AppState>) -> Router {
     Router::new()
         // ── Health ──────────────────────────────────────────────────────────
         .route("/health", get(health_check))
+        .route("/health/deep", get(health::health_deep))
         // ── Auth ────────────────────────────────────────────────────────────
         .route("/api/auth/register", post(auth::register))
         .route("/api/auth/login", post(auth::login))