Improve tracing (#5698)

* Improve tracing implementation

* Enable tracing in runtime interfaces

* Switch to `TRACE` level

substrate/primitives/tracing/src/lib.rs

@@ -0,0 +1,84 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Substrate tracing primitives and macros.
+//!
+//! To trace functions or invidual code in Substrate, this crate provides [`tracing_span`]
+//! and [`enter_span`]. See the individual docs for how to use these macros.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(feature = "std")]
+#[doc(hidden)]
+pub use tracing;
+
+/// Runs given code within a tracing span, measuring it's execution time.
+///
+/// If tracing is not enabled, the code is still executed.
+///
+/// # Example
+///
+/// ```
+/// sp_tracing::tracing_span! {
+///     "test-span";
+///     1 + 1;
+///     // some other complex code
+/// }
+/// ```
+#[macro_export]
+macro_rules! tracing_span {
+	(
+		$name:expr;
+		$( $code:tt )*
+	) => {
+		{
+			$crate::enter_span!($name);
+			$( $code )*
+		}
+	}
+}
+
+/// Enter a span.
+///
+/// The span will be valid, until the scope is left.
+///
+/// # Example
+///
+/// ```
+/// sp_tracing::enter_span!("test-span");
+/// ```
+#[macro_export]
+macro_rules! enter_span {
+	( $name:expr ) => {
+		let __tracing_span__ = $crate::if_tracing!(
+			$crate::tracing::span!($crate::tracing::Level::TRACE, $name)
+		);
+		let __tracing_guard__ = $crate::if_tracing!(__tracing_span__.enter());
+	}
+}
+
+/// Generates the given code if the tracing dependency is enabled.
+#[macro_export]
+#[cfg(feature = "std")]
+macro_rules! if_tracing {
+	( $if:expr ) => {{ $if }}
+}
+
+#[macro_export]
+#[cfg(not(feature = "std"))]
+macro_rules! if_tracing {
+	( $if:expr ) => {{}}
+}