feat: add tracing

tests/health_check.rs

@@ -1,8 +1,27 @@
 use learn_axum::configuration::{get_configuration, DatabaseSettings};
+use learn_axum::telemetry::{get_subscriber, init_subscriber};
+use once_cell::sync::Lazy;
 use sqlx::{Connection, Executor, PgConnection, PgPool};
 use tokio::net::TcpListener;
 use uuid::Uuid;
 
+/// Ensure that the `tracing` stack is only initialised once using `once_cell`
+static TRACING: Lazy<()> = Lazy::new(|| {
+    let default_filter_level = "info".to_string();
+    let subscriber_name = "test".to_string();
+    // We cannot assign the output of `get_subscriber` to a variable based on the
+    // value TEST_LOG` because the sink is part of the type returned by
+    // `get_subscriber`, therefore they are not the same type. We could work around
+    // it, but this is the most straight-forward way of moving forward.
+    if std::env::var("TEST_LOG").is_ok() {
+        let subscriber = get_subscriber(subscriber_name, default_filter_level, std::io::stdout);
+        init_subscriber(subscriber);
+    } else {
+        let subscriber = get_subscriber(subscriber_name, default_filter_level, std::io::sink);
+        init_subscriber(subscriber);
+    };
+});
+
 pub struct TestApp {
     pub address: String,
     pub db_pool: PgPool,
@@ -86,6 +105,10 @@ async fn subscribe_returns_a_200_for_valid_form_data() {
 }
 
 async fn spawn_app() -> TestApp {
+    // The first time `initialize` is invoked the code in `TRACING` is executed.
+    // All other invocations will instead skip execution.
+    Lazy::force(&TRACING);
+
     let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
     let address = format!("http://{}", listener.local_addr().unwrap());