Improve tracing (#5698)

* Improve tracing implementation

* Enable tracing in runtime interfaces

* Switch to `TRACE` level

substrate/primitives/runtime-interface/test/Cargo.toml

@@ -19,3 +19,4 @@ sp-runtime-interface-test-wasm-deprecated = { version = "2.0.0-dev", path = "../
 sp-state-machine = { version = "0.8.0-dev", path = "../../../primitives/state-machine" }
 sp-runtime = { version = "2.0.0-dev", path = "../../runtime" }
 sp-io = { version = "2.0.0-dev", path = "../../io" }
+tracing = "0.1.13"

substrate/primitives/runtime-interface/test/src/lib.rs

@@ -27,6 +27,8 @@ use sp_runtime_interface_test_wasm_deprecated::WASM_BINARY as WASM_BINARY_DEPREC
 use sp_wasm_interface::HostFunctions as HostFunctionsT;
 use sc_executor::CallInWasm;
 
+use std::{collections::HashSet, sync::{Arc, Mutex}};
+
 type TestExternalities = sp_state_machine::TestExternalities<sp_runtime::traits::BlakeTwo256, u64>;
 
 fn call_wasm_method<HF: HostFunctionsT>(binary: &[u8], method: &str) -> TestExternalities {
@@ -150,3 +152,47 @@ fn test_versionining_with_new_host_works() {
 		"test_versionning_works",
 	);
 }
+
+#[test]
+fn test_tracing() {
+	use tracing::span::Id as SpanId;
+
+	#[derive(Clone)]
+	struct TracingSubscriber(Arc<Mutex<Inner>>);
+
+	#[derive(Default)]
+	struct Inner {
+		spans: HashSet<&'static str>,
+	}
+
+	impl tracing::subscriber::Subscriber for TracingSubscriber {
+		fn enabled(&self, _: &tracing::Metadata) -> bool { true }
+
+		fn new_span(&self, span: &tracing::span::Attributes) -> tracing::Id {
+			let mut inner = self.0.lock().unwrap();
+			let id = SpanId::from_u64((inner.spans.len() + 1) as _);
+			inner.spans.insert(span.metadata().name());
+			id
+		}
+
+		fn record(&self, _: &SpanId, _: &tracing::span::Record) {}
+
+		fn record_follows_from(&self, _: &SpanId, _: &SpanId) {}
+
+		fn event(&self, _: &tracing::Event) {}
+
+		fn enter(&self, _: &SpanId) {}
+
+		fn exit(&self, _: &SpanId) {}
+	}
+
+	let subscriber = TracingSubscriber(Default::default());
+	let _guard = tracing::subscriber::set_default(subscriber.clone());
+
+	// Call some method to generate a trace
+	call_wasm_method::<HostFunctions>(&WASM_BINARY[..], "test_return_data");
+
+	let inner = subscriber.0.lock().unwrap();
+	assert!(inner.spans.contains("return_input_version_1"));
+	assert!(inner.spans.contains("ext_test_api_return_input_version_1"));
+}