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/backing/src/lib.rs

@@ -37,7 +37,7 @@ use polkadot_node_primitives::{
 	FromTableMisbehavior, Statement, SignedFullStatement, MisbehaviorReport, ValidationResult,
 };
 use polkadot_subsystem::{
-	jaeger::{self, JaegerSpan},
+	JaegerSpan, PerLeafSpan,
 	messages::{
 		AllMessages, AvailabilityStoreMessage, CandidateBackingMessage, CandidateSelectionMessage,
 		CandidateValidationMessage, PoVDistributionMessage, ProvisionableData,
@@ -923,9 +923,10 @@ impl util::JobTrait for CandidateBackingJob {
 
 	const NAME: &'static str = "CandidateBackingJob";
 
-	#[tracing::instrument(skip(keystore, metrics, rx_to, tx_from), fields(subsystem = LOG_TARGET))]
+	#[tracing::instrument(skip(span, keystore, metrics, rx_to, tx_from), fields(subsystem = LOG_TARGET))]
 	fn run(
 		parent: Hash,
+		span: Arc<JaegerSpan>,
 		keystore: SyncCryptoStorePtr,
 		metrics: Metrics,
 		rx_to: mpsc::Receiver<Self::ToJob>,
@@ -952,7 +953,7 @@ impl util::JobTrait for CandidateBackingJob {
 				}
 			}
 
-			let span = jaeger::hash_span(&parent, "run:backing");
+			let span = PerLeafSpan::new(span, "backing");
 			let _span = span.child("runtime-apis");
 
 			let (validators, groups, session_index, cores) = futures::try_join!(
@@ -1340,7 +1341,10 @@ mod tests {
 	) {
 		// Start work on some new parent.
 		virtual_overseer.send(FromOverseer::Signal(
-			OverseerSignal::ActiveLeaves(ActiveLeavesUpdate::start_work(test_state.relay_parent)))
+			OverseerSignal::ActiveLeaves(ActiveLeavesUpdate::start_work(
+				test_state.relay_parent,
+				Arc::new(JaegerSpan::Disabled),
+			)))
 		).await;
 
 		// Check that subsystem job issues a request for a validator set.