v0.1.2-pre.005

crates/ksp-logging-lib/tests/overhead.rs

@@ -0,0 +1,47 @@
+// file: crates/ksp-logging-lib/tests/overhead.rs
+// version: 1
+
+//! Diagnostic gross-overhead probe for the reload layer used by KSP Logging.
+
+use tracing_subscriber::layer::SubscriberExt; // rust-rules: trait-import
+
+const TEST_TARGET: &str = "ksp-logging-lib";
+const ITERATIONS: u64 = 200_000;
+
+fn emit_probe_events() {
+    for sequence in 0..ITERATIONS {
+        tracing::trace!(target: TEST_TARGET, sequence, "reload overhead probe");
+    }
+}
+
+fn trace_filter() -> tracing_subscriber::filter::Targets {
+    return tracing_subscriber::filter::Targets::new()
+        .with_default(tracing_subscriber::filter::LevelFilter::OFF)
+        .with_target(TEST_TARGET, tracing_subscriber::filter::LevelFilter::TRACE);
+}
+
+#[test]
+#[ignore = "diagnostic timing probe; run explicitly with --ignored --nocapture"]
+fn reload_layer_overhead_remains_within_a_gross_regression_guardrail() {
+    let baseline_subscriber = tracing_subscriber::registry().with(trace_filter());
+    let baseline_start = std::time::Instant::now();
+    tracing::subscriber::with_default(baseline_subscriber, || {
+        emit_probe_events();
+        return;
+    });
+    let baseline_elapsed = baseline_start.elapsed();
+    let (reload_layer, _reload_handle) = tracing_subscriber::reload::Layer::new(trace_filter());
+    let reload_subscriber = tracing_subscriber::registry().with(reload_layer);
+    let reload_start = std::time::Instant::now();
+    tracing::subscriber::with_default(reload_subscriber, || {
+        emit_probe_events();
+        return;
+    });
+    let reload_elapsed = reload_start.elapsed();
+    let gross_ceiling = baseline_elapsed.saturating_mul(100).saturating_add(std::time::Duration::from_millis(100));
+    println!("KSP reload overhead probe: baseline={baseline_elapsed:?}, reload={reload_elapsed:?}, iterations={ITERATIONS}");
+    assert!(
+        reload_elapsed <= gross_ceiling,
+        "reload layer exceeded the gross regression guardrail: baseline={baseline_elapsed:?}, reload={reload_elapsed:?}"
+    );
+}