Add one Jaeger span per relay parent (#2196)

* Add one Jaeger span per relay parent

This adds one Jaeger span per relay parent, instead of always creating
new spans per relay parent. This should improve the UI view, because
subsystems are now grouped below one common span.

* Fix doc tests

* Replace `PerLeaveSpan` to `PerLeafSpan`

* More renaming

* Moare

* Update node/subsystem/src/lib.rs

Co-authored-by: Andronik Ordian <write@reusable.software>

* Skip the spans

* Increase `spec_version`

Co-authored-by: Andronik Ordian <write@reusable.software>

polkadot/node/core/candidate-selection/src/lib.rs

@@ -25,7 +25,7 @@ use futures::{
 };
 use sp_keystore::SyncCryptoStorePtr;
 use polkadot_node_subsystem::{
-	jaeger,
+	jaeger, JaegerSpan, PerLeafSpan,
 	errors::ChainApiError,
 	messages::{
 		AllMessages, CandidateBackingMessage, CandidateSelectionMessage, CollatorProtocolMessage,
@@ -39,7 +39,7 @@ use polkadot_node_subsystem_util::{
 use polkadot_primitives::v1::{
 	CandidateReceipt, CollatorId, CoreState, CoreIndex, Hash, Id as ParaId, PoV,
 };
-use std::pin::Pin;
+use std::{pin::Pin, sync::Arc};
 use thiserror::Error;
 
 const LOG_TARGET: &'static str = "candidate_selection";
@@ -95,12 +95,13 @@ impl JobTrait for CandidateSelectionJob {
 	#[tracing::instrument(skip(keystore, metrics, receiver, sender), fields(subsystem = LOG_TARGET))]
 	fn run(
 		relay_parent: Hash,
+		span: Arc<JaegerSpan>,
 		keystore: Self::RunArgs,
 		metrics: Self::Metrics,
 		receiver: mpsc::Receiver<CandidateSelectionMessage>,
 		mut sender: mpsc::Sender<FromJobCommand>,
 	) -> Pin<Box<dyn Future<Output = Result<(), Self::Error>> + Send>> {
-		let span = jaeger::hash_span(&relay_parent, "candidate-selection:run");
+		let span = PerLeafSpan::new(span, "candidate-selection");
 		async move {
 			let _span = span.child("query-runtime");
 			let (groups, cores) = futures::try_join!(