Complex headers+messages Millau<->Rialto relay (#878)

* complex headers+messages relay

* post-merge fix

* fix + test issue with on-demand not starting

bridges/relays/exchange/src/exchange_loop.rs

@@ -78,6 +78,11 @@ impl<BlockNumber: Clone + Copy> TransactionProofsRelayStorage for InMemoryStorag
 	}
 }
 
+/// Return prefix that will be used by default to expose Prometheus metrics of the exchange loop.
+pub fn metrics_prefix<P: TransactionProofPipeline>() -> String {
+	format!("{}_to_{}_Exchange", P::SOURCE_NAME, P::TARGET_NAME)
+}
+
 /// Run proofs synchronization.
 pub async fn run<P: TransactionProofPipeline>(
 	storage: impl TransactionProofsRelayStorage<BlockNumber = BlockNumberOf<P>>,
@@ -89,12 +94,9 @@ pub async fn run<P: TransactionProofPipeline>(
 	let exit_signal = exit_signal.shared();
 
 	relay_utils::relay_loop(source_client, target_client)
-		.with_metrics(
-			format!("{}_to_{}_Exchange", P::SOURCE_NAME, P::TARGET_NAME),
-			metrics_params,
-		)
-		.loop_metric(ExchangeLoopMetrics::default())?
-		.standalone_metric(GlobalMetrics::default())?
+		.with_metrics(Some(metrics_prefix::<P>()), metrics_params)
+		.loop_metric(|registry, prefix| ExchangeLoopMetrics::new(registry, prefix))?
+		.standalone_metric(|registry, prefix| GlobalMetrics::new(registry, prefix))?
 		.expose()
 		.await?
 		.run(|source_client, target_client, metrics| {

bridges/relays/exchange/src/exchange_loop_metrics.rs

@@ -17,7 +17,9 @@
 //! Metrics for currency-exchange relay loop.
 
 use crate::exchange::{BlockNumberOf, RelayedBlockTransactions, TransactionProofPipeline};
-use relay_utils::metrics::{register, Counter, CounterVec, GaugeVec, Metrics, Opts, Registry, U64};
+use relay_utils::metrics::{
+	metric_name, register, Counter, CounterVec, GaugeVec, Opts, PrometheusError, Registry, U64,
+};
 
 /// Exchange transactions relay metrics.
 #[derive(Clone)]
@@ -30,31 +32,38 @@ pub struct ExchangeLoopMetrics {
 	processed_transactions: CounterVec<U64>,
 }
 
-impl Metrics for ExchangeLoopMetrics {
-	fn register(&self, registry: &Registry) -> Result<(), String> {
-		register(self.best_block_numbers.clone(), registry).map_err(|e| e.to_string())?;
-		register(self.processed_blocks.clone(), registry).map_err(|e| e.to_string())?;
-		register(self.processed_transactions.clone(), registry).map_err(|e| e.to_string())?;
-		Ok(())
-	}
-}
-
-impl Default for ExchangeLoopMetrics {
-	fn default() -> Self {
-		ExchangeLoopMetrics {
-			best_block_numbers: GaugeVec::new(
-				Opts::new("best_block_numbers", "Best finalized block numbers"),
-				&["type"],
-			)
-			.expect("metric is static and thus valid; qed"),
-			processed_blocks: Counter::new("processed_blocks", "Total number of processed blocks")
-				.expect("metric is static and thus valid; qed"),
-			processed_transactions: CounterVec::new(
-				Opts::new("processed_transactions", "Total number of processed transactions"),
-				&["type"],
-			)
-			.expect("metric is static and thus valid; qed"),
-		}
+impl ExchangeLoopMetrics {
+	/// Create and register exchange loop metrics.
+	pub fn new(registry: &Registry, prefix: Option<&str>) -> Result<Self, PrometheusError> {
+		Ok(ExchangeLoopMetrics {
+			best_block_numbers: register(
+				GaugeVec::new(
+					Opts::new(
+						metric_name(prefix, "best_block_numbers"),
+						"Best finalized block numbers",
+					),
+					&["type"],
+				)?,
+				registry,
+			)?,
+			processed_blocks: register(
+				Counter::new(
+					metric_name(prefix, "processed_blocks"),
+					"Total number of processed blocks",
+				)?,
+				registry,
+			)?,
+			processed_transactions: register(
+				CounterVec::new(
+					Opts::new(
+						metric_name(prefix, "processed_transactions"),
+						"Total number of processed transactions",
+					),
+					&["type"],
+				)?,
+				registry,
+			)?,
+		})
 	}
 }