Telemetry per node (#7463)

substrate/client/tracing/src/logging/layers/prefix_layer.rs

@@ -0,0 +1,86 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2021 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+use tracing::{span::Attributes, Id, Subscriber};
+use tracing_subscriber::{layer::Context, registry::LookupSpan, Layer};
+
+/// Span name used for the logging prefix. See macro `sc_tracing::logging::prefix_logs_with!`
+pub const PREFIX_LOG_SPAN: &str = "substrate-log-prefix";
+
+/// A `Layer` that captures the prefix span ([`PREFIX_LOG_SPAN`]) which is then used by
+/// [`EventFormat`] to prefix the log lines by customizable string.
+///
+/// See the macro `sc_cli::prefix_logs_with!` for more details.
+pub struct PrefixLayer;
+
+impl<S> Layer<S> for PrefixLayer
+where
+	S: Subscriber + for<'a> LookupSpan<'a>,
+{
+	fn new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>) {
+		let span = ctx
+			.span(id)
+			.expect("new_span has been called for this span; qed");
+
+		if span.name() != PREFIX_LOG_SPAN {
+			return;
+		}
+
+		let mut extensions = span.extensions_mut();
+
+		if extensions.get_mut::<Prefix>().is_none() {
+			let mut s = String::new();
+			let mut v = PrefixVisitor(&mut s);
+			attrs.record(&mut v);
+
+			if !s.is_empty() {
+				let fmt_fields = Prefix(s);
+				extensions.insert(fmt_fields);
+			}
+		}
+	}
+}
+
+struct PrefixVisitor<'a, W: std::fmt::Write>(&'a mut W);
+
+macro_rules! write_node_name {
+	($method:ident, $type:ty, $format:expr) => {
+		fn $method(&mut self, field: &tracing::field::Field, value: $type) {
+			if field.name() == "name" {
+				let _ = write!(self.0, $format, value);
+			}
+		}
+	};
+}
+
+impl<'a, W: std::fmt::Write> tracing::field::Visit for PrefixVisitor<'a, W> {
+	write_node_name!(record_debug, &dyn std::fmt::Debug, "[{:?}] ");
+	write_node_name!(record_str, &str, "[{}] ");
+	write_node_name!(record_i64, i64, "[{}] ");
+	write_node_name!(record_u64, u64, "[{}] ");
+	write_node_name!(record_bool, bool, "[{}] ");
+}
+
+#[derive(Debug)]
+pub(crate) struct Prefix(String);
+
+impl Prefix {
+	pub(crate) fn as_str(&self) -> &str {
+		self.0.as_str()
+	}
+}