feat: harden community production foundation through story 1.5

crates/crank-observability/tests/request_correlation.rs

@@ -0,0 +1,60 @@
+use std::sync::Arc;
+
+use crank_observability::{current_request_correlation, with_request_correlation};
+
+#[tokio::test]
+async fn concurrent_request_correlation_is_task_local() {
+    let barrier = Arc::new(tokio::sync::Barrier::new(2));
+    let first = observe(
+        "request-first",
+        "0af7651916cd43dd8448eb211c80319c",
+        Arc::clone(&barrier),
+    );
+    let second = observe(
+        "request-second",
+        "1af7651916cd43dd8448eb211c80319c",
+        barrier,
+    );
+    let (first, second) = tokio::join!(first, second);
+
+    assert_eq!(
+        first,
+        (
+            Some("request-first".to_owned()),
+            Some("0af7651916cd43dd8448eb211c80319c".to_owned()),
+        )
+    );
+    assert_eq!(
+        second,
+        (
+            Some("request-second".to_owned()),
+            Some("1af7651916cd43dd8448eb211c80319c".to_owned()),
+        )
+    );
+    assert_eq!(current_request_correlation(), (None, None));
+}
+
+#[tokio::test]
+async fn invalid_correlation_strings_never_enter_task_local_state() {
+    let observed = with_request_correlation(
+        "bad request id".to_owned(),
+        "CANARY-NOT-A-TRACE-ID".to_owned(),
+        async { current_request_correlation() },
+    )
+    .await;
+
+    assert_eq!(observed, (None, None));
+}
+
+async fn observe(
+    request_id: &str,
+    trace_id: &str,
+    barrier: Arc<tokio::sync::Barrier>,
+) -> (Option<String>, Option<String>) {
+    with_request_correlation(request_id.to_owned(), trace_id.to_owned(), async move {
+        barrier.wait().await;
+        tokio::task::yield_now().await;
+        current_request_correlation()
+    })
+    .await
+}